Product depletion sensor

Abstract

A product depletion sensor can include a housing having a first surface and defining a flow channel. The circuit board can be coupled to the first surface of the housing and support the thermistor bridge. The thermistor bridge can be arranged such that some thermistors are located in the first sensing region and other thermistors are located in the second sensing region. The housing can be configured such that a thermal resistance between the flow channel and the first sensing region is lower than a thermal resistance between the flow channel and the second sensing region, and / or fluid flowing in the flow channel is directed more toward the first sensing region than the second sensing region. The liquid in the flow channel can differently affect the thermal behavior of the thermistors in the first sensing region and the second sensing region, and can be used to determine whether the liquid flows through the sensor.

Description

Cross-reference to related applications

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 581,853, filed on September 11, 2023, the contents of which are incorporated herein by reference in their entirety. Background Technology

[0002] Fluid distribution systems typically deliver large quantities of fluid to one or more components within a system. In some applications, fluid distribution systems can deliver small amounts of fluid. For example, in the medical field, fluid distribution systems can be used to deliver small amounts of fluid to a patient's vascular system. However, in other applications, fluid distribution systems can deliver much larger quantities of fluid. For instance, in large hotels or other laundries or restaurant facilities, fluid distribution systems may need to continuously deliver large quantities of detergent, rinsing agent, bleach, or other cleaning agents.

[0003] In fluid delivery systems that transport large volumes of fluid, the fluid can be supplied automatically. In such systems, the supply source (such as a bottle) and the fluid delivery lines (such as a supply pipe) are often integrated with the device that delivers the fluid, such as a dishwashing machine or washing machine. This makes it more difficult for the operator to check the amount of remaining fluid in the supply source and often results in the system running out of fluid, for example, during a cleaning cycle. Summary of the Invention

[0004] Various aspects of this disclosure relate to product depletion (OOP) sensors. Existing OOP sensors typically detect the absence of fluid in the sensor, thus indicating when the delivery system is empty (filled with air). However, many products are delivered from compressible bottles, and the tubing in the delivery system remains filled with fluid when the product is depleted. Conventional OOP sensors fail to identify delivery failures when the product is in the tubing but not moving. Some aspects of this disclosure utilize pulse-mode thermistor excitation in the OOP sensor, which in some examples allows the detection of three distinct states: “empty (air)”, “product present but not flowing”, and “product flowing”. Such improvements to existing systems can be used to identify when the product is depleted and no longer flowing, but rather remains present in the sensor. Additionally or alternatively, in some capacitance-dependent OOP sensors, viscous liquid coating the inside of the sensor can affect sensor readings even when the liquid is no longer flowing and even when there is no significant amount of stagnant liquid.

[0005] Additionally or alternatively, some OOP sensors not only detect the presence or absence of a product, but also provide information about the normal functioning of the liquid delivery system, such as detecting air bubbles in the flow line, issuing a warning if the corresponding pump is not working, or indicating whether the liquid delivery line is damaged. Various settings and thresholds can be calibrated and customized for a given system so that the OOP sensor can accurately determine various flow information based on the specific configuration and / or purpose of the system.

[0006] Some OOP sensors according to this disclosure include a housing having a first surface and defining a flow channel. An inlet and an outlet fluidly connect the flow channel to the outside of the housing. A circuit board is coupled to the first surface of the housing and supports a thermistor bridge having multiple thermistors.

[0007] The thermistors in the thermistor bridge can be located in a first sensing region and a second sensing region, and the housing of the OOP sensor can be configured such that the thermal resistance between the flow channel and the first sensing region is lower than the thermal resistance between the flow channel and the second sensing region, and / or the fluid flowing in the flow channel is directed more towards the first sensing region than the second sensing region. In some such cases, the fluid flowing through the flow channel will have a greater thermal effect on the thermistors in the first sensing region than on the thermistors in the second sensing region. The different thermal effects on the different thermistors in the thermistor bridge caused by the fluid flowing through the flow channel can provide information about the presence of fluid flowing through the flow channel.

[0008] The thermistor bridge includes a first branch and a second branch. The first branch has a first thermistor connected in series with a second thermistor and a first point located between the first and second thermistors. The second branch has a third thermistor connected in series with a fourth thermistor and a second point located between the third and fourth thermistors. The first and second branches can be arranged in parallel between the power supply side and the reference side of the thermistor bridge, such that the first and third thermistors are coupled to the power supply side of the thermistor bridge, and the second and fourth thermistors are coupled to the reference side of the thermistor bridge.

[0009] The controller can be configured to allow current to flow from a power source to a thermistor bridge for a duration of heating. The controller can measure the thermal behavior of the thermistor bridge to determine the flow state of the fluid through the flow channels, such as whether the fluid flows through the flow channels, is stagnant in the flow channels, or is not present in the flow channels. The controller can provide multiple measurement pulses to the thermistor bridge at a measurement frequency, receiving a measurement signal value representing the voltage between a first point and a second point of the thermistor bridge during each measurement pulse, and determining the average measurement signal value. The controller can determine the flow state through the flow channels based on the average measurement signal value.

[0010] In some cases, determining the flow state within a flow channel includes determining that fluid is flowing in the flow channel if the average measured signal value meets a first predetermined threshold condition. Additionally or alternatively, in some cases, determining the flow state within a flow channel includes determining that fluid is not present in the flow channel if the average measured signal value meets a second predetermined threshold condition. The first predetermined threshold condition may include an average measured signal value below a first predetermined threshold, and the second predetermined threshold may include an average measured signal value above a second predetermined threshold, which is higher than the first predetermined threshold. Determining the flow state may further include determining that fluid is present in the flow channel but is not flowing if the average measured signal value is between the first predetermined threshold and the second predetermined threshold. The absence of liquid when liquid is expected can indicate a product depletion event.

[0011] Temperature information can be used to correct for the effect of temperature on the behavior of a thermistor bridge. The controller can be configured to receive a second signal representing the temperature of the fluid in the flow channel. In some examples, the controller can use the second signal to calculate the temperature. The second signal can represent the voltage drop across the thermistors in the thermistor bridge or individual thermistors. The second signal can be used to calculate a correction measurement signal value.

[0012] The differences in thermal behavior of thermistors in different sensing regions allow for easy differentiation of flow states within a flow channel, such as the time when liquid flows through the sensor's flow channel, when liquid is not present in the flow channel, or when liquid stagnates within the flow channel. Temperature measurements can be used to correct the measured signal value to compensate for the effect of temperature on thermal behavior. Attached Figure Description

[0013] Figure 1A This is a diagram illustrating an example fluid flow system with a product depletion sensing system that detects the presence and / or absence of a product to be dispensed.

[0014] Figure 1BThis is a diagram illustrating another example system that distributes multiple products.

[0015] Figure 2 An example schematic diagram of various aspects of a product depletion sensing system is shown.

[0016] Figure 3 shows a side view of an example configuration of the product depletion sensor.

[0017] Figure 4A An example cross-sectional view of an implementation of a product depletion sensor is shown.

[0018] Figure 4B It shows Figure 4A The product exhausts the sensor's exploded perspective view.

[0019] Figure 4C It shows Figure 4A Another breakdown perspective of the product's depleted sensor.

[0020] Figure 5A An example cross-sectional view of an implementation of a product depletion sensor is shown.

[0021] Figure 5B It shows Figure 5A The product exhausts the sensor's exploded perspective view.

[0022] Figure 5C It shows Figure 5A Another breakdown perspective of the product's depleted sensor.

[0023] Figure 6A An example cross-sectional view of an implementation of a product depletion sensor is shown.

[0024] Figure 6B It shows Figure 6A The product exhausts the sensor's exploded perspective view.

[0025] Figure 6C It shows Figure 6A Another breakdown perspective of the product's depleted sensor.

[0026] Figure 7 An example cross-sectional view of an implementation of a product depletion sensor is shown.

[0027] Figure 8 An example of a product-depleted sensor is shown.

[0028] Figure 9 This is an example voltage-to-time graph showing the voltage in a product depletion sensing system.

[0029] Figure 10 An example graph of the average measured signal value over time is shown in a product depletion sensing system.

[0030] Figure 11 An example current pulse through a thermistor bridge is shown for an example implementation.

[0031] Figure 12 Example readings measured at input 7a and example corresponding flow state indications based on these readings are shown.

[0032] Figure 13 Example graphs showing the variation of measured signals with temperature under various flow conditions are shown.

[0033] Figure 14 Example graphs are shown of raw sensor readings and corrected sensor readings at different temperature ranges under constant flow rates.

[0034] Figure 15 The diagram shows calibrated sensor readings for different flow states within different temperature ranges.

[0035] Figure 16 An alternative exemplary schematic diagram is shown, illustrating various aspects of a product depletion sensing system that includes an independent thermistor.

[0036] Figure 17A An example cross-sectional view of an implementation of an OOP sensor that includes a separate thermistor in addition to the thermistor bridge is shown.

[0037] Figure 17B It shows Figure 17A An exploded perspective view of the OOP sensor.

[0038] Figure 17C It shows Figure 17A Another breakdown perspective of the product's depleted sensor.

[0039] Figure 18A An example graph showing the variation of the measurement signal with measurement frequency during a constant fluid flow through an OOP sensor is shown.

[0040] Figure 18B An example graph showing the relationship between the measurement frequency required to maintain a constant measurement signal and temperature is shown.

[0041] Figure 19 An example measurement signal is shown for a constant fluid flow through an OOP sensor, at a constant measurement frequency and a measurement frequency that varies linearly with temperature.

[0042] Figure 20 An example graph of the measurement signal over time, which can be used to detect bubbles in an OOP sensor, is shown. Detailed Implementation

[0043] The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of this disclosure in any way. In fact, the following description provides some practical illustrations of examples for implementing this disclosure. Examples of construction, materials, dimensions, and manufacturing processes are provided for selected elements, and all other elements use construction, materials, dimensions, and manufacturing processes known to one of ordinary skill in the art. Those skilled in the art will recognize that many of the examples mentioned have multiple suitable alternatives.

[0044] Figure 1A This is a diagram illustrating an example fluid flow system having a product depletion sensing system for detecting the presence and / or absence of a product to be dispensed. System 100A includes a controller 104, a pump 102, and a product reservoir 103. Pump 102 draws product (e.g., a liquid product) from reservoir 103 and delivers the product to dispensing point 105. Pump 102 draws product from product reservoir 103 via input fluid delivery line 120 and supplies fluid to dispensing point 105 via output fluid delivery line 122. Product reservoir 103 may contain any of a variety of different types of products with different transparency and / or turbidity. In some embodiments, product depletion (“OOP”) sensor 200 is configured to detect the presence or absence of fluid, for example, flowing in input fluid delivery line 120 and / or output fluid delivery line 122. In the illustrated example, OOP sensor 200 is positioned in line with input fluid delivery line 120 and may be configured to determine, for example, the presence or absence of fluid (e.g., a liquid) in the line.

[0045] Controller 104 may communicate with pump 102 via connection 118. In some examples, pump 102 draws product from reservoir 103 or stops pumping under the control of controller 104. In some examples, controller 104 may communicate with dispensing unit 105 via another connection (not shown).

[0046] In some examples, controller 104 includes processor 112, user interface 108, and memory 114. In some examples, the system may include multiple controllers 104. Signals generated by OOP sensor 200 may be transmitted to controller 104 via connection 116. Connection 116 may transmit digital or analog signals. Connection 116 may include, for example, a standard I2C connection. However, any suitable connection / communication channel known in the art may be used. Controller 104 may also include at least one external connection 124, such as the Internet, telephone, wireless, or other connections, for enabling external communication.

[0047] In some examples, memory 114 stores software for running controller 104 and also stores data generated or used by processor 112. In some examples, processor 112 runs software stored in memory 114 to manage the operation of controller 104. User interface 108 may be as simple as a few light-emitting diodes (LEDs) and / or user-operable buttons or may include a display, keyboard or keypad, mouse, or other suitable mechanism for communicating with the user.

[0048] The dispensing point 105 may be the final point of use for the product or some other intermediate location. For example, when the fluid flow system 100A is used in a commercial laundromat or kitchen application, the dispensing point 105 may be a washing machine or dishwashing machine, in which case the product may be dispensed into the dispensing mechanism of the switching unit or directly into the washing environment. In the example described, the dispensed product may include laundry or dishwashing detergent, fabric softener, bleach, disinfectant, rinse aid, etc. As another example, when the fluid dispensing system is used in a hotel, commercial, industrial, or other application in which cleaning work is performed by waiters, the dispensing point 105 may be a bucket, a tub, or other container into which the product is dispensed. The dispensing point 105 may also be a hose or other tube that guides the fluid from thereto to the desired location. It should be understood that the product depletion sensing system can be used in many different applications in which fluid is dispensed, and this disclosure is not limited to this aspect. Examples of applications in which the product depletion sensing system can be used include laundry applications, dishwashing applications, commercial cleaning operations, food preparation and packaging applications, industrial processes, healthcare applications, vehicle care applications, and other applications known in the art.

[0049] The inlet fluid delivery line 120 and the outlet fluid delivery line 122 may be implemented using any type of flexible or non-flexible tubing, depending on the application. This tubing may be transparent, translucent, braided, or other types of tubing. The tubing may be made of polyethylene, ethylene-vinyl acetate, polytetrafluoroethylene, or any other suitable material. For simplicity and not limitation, the inlet fluid delivery line 120 and the outlet fluid delivery line may be referred to as “inlet pipe 120” and “outlet pipe 122”, respectively. The inlet pipe 120, the outlet pipe 122, and the pump 102 may be referred to herein as “dispensing channels.” The pump 102 may be any type of pumping mechanism that supplies fluid from the product reservoir 103 to the dispensing point 105. For example, the pump 102 may include a peristaltic pump or other forms of continuous pump, positive displacement pump, or other types of pump suitable for a particular application.

[0050] exist Figure 1AIn the example system shown, the OOP sensor 200 is positioned to detect the presence and / or absence of product in the input tube 120. During operation, when the fluid dispensing system attempts to dispense a cycle from the product reservoir 103, which has remaining product, the input tube 120 will also contain product. In some examples, the OOP sensor 200 continuously sends signals to the controller 104, and the controller 104 interprets those signals to determine whether product is present or absent in the input tube 120. Over time, as operation continues and more and more product is dispensed, the product reservoir 103 becomes substantially empty. Because product is no longer available for dispensing, the input tube 120 also becomes substantially empty. When the controller 104 determines, based on the signals from the OOP sensor 200, that a product depletion event has occurred, the controller 104 may generate a product depletion warning.

[0051] In some implementations, a "product exhaustion event" (e.g., an event in which controller 104 detects the absence of fluid within input pipe 120) is determined relative to one or more predefined product exhaustion thresholds. When controller 104 detects a product exhaustion event, controller 104 may generate one or more alerts, including visual and / or audible product exhaustion alerts displayed on user interface 108 (such as text or graphics with or without accompanying sound). Additionally or alternatively, controller 104 may initiate and send product exhaustion message service calls (such as via pager, email, text message, etc.) to a technology service provider via external connection 124.

[0052] When an alert is activated to indicate a product depletion event, a user (such as an employee or service technician) can manually refill the product reservoir 103. In this embodiment, the user can temporarily interrupt or shut down the operation of the fluid flow system before refilling the product reservoir 103. In one example, the user can do this by entering a command into the controller 104 to stop the operation of the pump 102 and / or the dispensing unit 105. In another example, the user can do this by entering a control command via the user interface 108 of the controller 104 to silence audible and / or visual warnings for a period of time. In yet another example, the user can do this by entering a control command via the user interface 108 of the controller 104 to stop the operation of the pump 102 and / or the dispensing unit 105. In yet another example, the user can manually turn off the pump 102 and / or the dispensing unit 105. After the user has refilled the product reservoir 103, the user can manually restart the pump 102 and / or the dispensing unit 105. This can be done by inputting a control command into the controller 104, or by inputting a control command via the user interface 108 to cause the controller 104 (e.g., via connection 118) to send a control signal to restart the pump 102 and / or the dispensing unit 105. The controller 104 can further reset or clear the warning at appropriate times (e.g., after the user manually clears it, after the product reservoir 103 has been refilled, or after the system has been restarted).

[0053] In response to a product depletion event, controller 104 may automatically stop pump 102 and / or dispensing section 105 and / or automatically stop dispensing section 105 upon detecting a product depletion event. In one example, controller 104 may send a control signal to pump 102 and / or dispensing section 105 to temporarily stop the operation of the corresponding components without user intervention. Controller 104 may then restart pump 102 and / or dispensing section 105 after receiving input from the user that the product reservoir 103 has been refilled. In another example, controller 104 may temporarily stop pump 102 and / or dispensing section 105 without user intervention. System controller may then send a signal to restart pump 102 and / or dispensing section 105 after receiving input from the user that the product reservoir 103 has been refilled.

[0054] The OOP sensor 200 or controller 104 can also generate a visual indicator indicating the presence of fluid within the input tube 120. For example, one color of light (such as green) can be used to indicate that fluid is flowing through the OOP sensor 200, indicating that the product reservoir 103 has remaining product, while another color of light (such as red or flashing) can be used to indicate that fluid is not flowing through the OOP sensor 200, indicating that the product reservoir 103 is empty and needs to be refilled.

[0055] Figure 1BThis is a diagram illustrating another example system for dispensing multiple products. For this purpose, system 100B includes multiple product channels (A to N), each having an associated product reservoir 103A to 103N, pumps 102A to 102N, a controller 104, and dispensing points 105A to 105N. Pumps 102A to 102N are included in pump assembly 101. Pumps 102A to 102N draw fluid from the corresponding product reservoirs 103A to 103N through inlet pipes 120A to 120N and supply fluid to one of the dispensing points 105A to 105N through inlet pipes 122A to 122N. Each product reservoir 103A to 103N may contain any of a variety of different types of products. OOP sensors 200A to 200N detect the presence and / or absence of the product dispensed in each corresponding dispensing channel.

[0056] although Figure 1B The illustrated system 100B shows each distribution channel having its own dedicated product reservoir 103, input pipe 120, input pipe 122, pump 102, target location 105, and OOP sensor 200; however, it should be understood that each distribution channel need not be a one-to-one correspondence. For example, sensors 200A to 200N can be implemented in a single unit, with the input pipe of each distribution channel arranged through said single unit. Alternatively, various combinations of one channel per sensor or two or more channels per sensor can be used, and this disclosure is not limited to this aspect.

[0057] same, Figure 1B The example pump assembly 101 includes multiple pumps 102A to 102N, each for each dispensed product. However, it should be understood that there need not be a one-to-one correspondence between pumps 102A to 102N and the dispensing channels. For example, some dispensed products may share one or more pumps, which switch from one dispensed product to another under the control of controller 104. One or more pumps 102A to 102N supply fluid from one of the product reservoirs 103A to 103B to the appropriate dispensing sites 105A to 105N.

[0058] It should also be understood that any of sensors 200A to 200N can also be positioned to detect the presence and / or absence of a product within output tubes 122A to 122N, but not within input tubes 120A to 120N, such as... Figure 1B As shown, and in some cases, the placement of sensors 200A to 200N may be more of a convenience issue than a system performance issue.

[0059] In some examples, controller 104 may be coupled to pump assembly 101 via connection 118. Through connection 118, controller 104 is able to communicate with pump assembly 101, thereby effectively controlling the operation of each individual pump 102 (e.g., temporary stop or start operation, as previously referenced). Figure 1A (As described).

[0060] Depending on the application, the controller 104 may also communicate with one or more distribution units 105A to 105N.

[0061] Each OOP sensor 200A to 200N detects the presence and / or absence of fluid in its corresponding input tube 120A to 120N. Controller 104 is coupled to each sensor 200A to 200N via corresponding connections 116A to 116N. Controller 104 monitors signals received from each OOP sensor 200A to 200N and can respond to any detected product depletion event as described above. For example, if the system controller detects one or more product depletion events, controller 104 can generate a visual or audible warning or display a message on user interface 108. The visual or audible warning and / or message displayed on user interface 108 and / or messages sent via pager, email, or text message, etc., will indicate which product receptacles 103A to 103N are empty, thus informing the user which product receptacle needs to be filled. In some examples, controller 104 may also automatically and temporarily stop and then restart pumps 102A to 102N corresponding to empty product reservoirs 103A to 103N and / or initiate an automatic refill cycle for the empty product reservoirs, as described above. In other examples, pumps 102A to 102N and / or dispensing sections 105A to 105N may be stopped and restarted automatically or manually with or without communication from the controller, as described above regarding Figure 1A As described.

[0062] Despite Figure 1B In this diagram, each sensor assembly is shown as having a dedicated connection to controller 104, but it should be understood that sensors 200A to 200N can be connected to controller 104 in any of several different ways. For example, sensors 200A to 200N can be daisy-chained to controller 104. In this example, controller 104 is directly coupled to the first OOP sensor 200A via connection 116A, and each subsequent OOP sensor 200B to 200N is coupled to the next sensor assembly, etc. Communication protocols for identifying each OOP sensor 200A to 200N and communicating individually with each OOP sensor can also be used. However, it should be understood that this disclosure is not limited to the specific architecture by which sensors 200A to 200N connect and communicate with controller 104, and the system can be configured in many different ways known to those skilled in the art.

[0063] Figure 2 An example schematic diagram of various aspects of a product depletion sensing system is shown. In the illustrated example, the thermistor bridge 10 includes a plurality of thermistors, including a first thermistor 1a, a second thermistor 2b, a third thermistor 2a, and a fourth thermistor 1b. In the illustrated example, the thermistor bridge 10 includes a first branch that includes the first thermistor 1a connected in series with the second thermistor 2b, wherein a first point 11 is located between the first thermistor 1a and the second thermistor 2b. Figure 2 The thermistor bridge 10 also includes a second branch comprising a third thermistor 2a connected in series with the fourth thermistor 1b, wherein a second point 12 is located between the third thermistor 2a and the fourth thermistor 1b. In some examples, as described elsewhere herein, the first thermistor 1a and the fourth thermistor 1b form a first pair of thermistors 21, and the second thermistor 2b and the third thermistor 2a form a second pair of thermistors 22.

[0064] As shown in the figure, the first and second branches are arranged in parallel between the power supply side 15 and the reference side 16 of the thermistor bridge 10. In the illustrated example, the first thermistor 1a and the third thermistor 2a are coupled to the power supply side 15 of the thermistor bridge 10, and the second thermistor 2b and the fourth thermistor 1b are coupled to the reference side 16 of the thermistor bridge 10.

[0065] Figure 2 The example system includes a power supply 6, which is coupled to the supply side 15 of the thermistor bridge 10 via a switch 4 and a current-limiting resistor 3. In some examples, the power supply 6 includes a DC power supply configured to output a DC voltage. In some examples, the power supply 6 is configured to output a constant voltage, such as 5VDC. In other examples, the power supply 6 may have a controllable output. The reference side 16 of the thermistor bridge 10 is coupled to a reference potential 25, such as system ground. In various examples, the switch 4 may include any type of switch capable of selectively interrupting the flow of current, such as a mechanical switch or a transistor. During operation, if the switch 4 is in the ON state, current can flow from the power supply 6 through the switch 4 and the current-limiting resistor 3 to the supply side 15 of the thermistor bridge 10, and through the branches of the thermistor bridge 10 to the reference side 16.

[0066] Figure 2 The system includes an analog-to-digital converter (ADC) 7 having a first differential input 7a and a second differential input 7b. Figure 2In the example, the first input 7a of ADC 7 includes an input coupled to a first point 11 and a second point 12 of the thermistor bridge 10. Therefore, in some examples, the first input 7a of ADC 7 is configured to receive a signal representing the voltage difference between the first point 11 and the second point 12. Additionally, in Figure 2 In the example, the second input 7b of ADC 7 includes an input coupled to the second point 12 of the thermistor bridge 10 and the reference potential 25. Therefore, in some examples, the second input 7b of ADC 7 is configured to receive a signal representing the voltage difference between the second point 12 and the reference voltage.

[0067] Figure 2 The system includes a controller 5 that communicates with the ADC 7, switch 4, and power supply 6. In some examples, the controller 5 is configured to receive, for example, a measured signal value representing the voltage between a first point 11 and a second point 12 from the ADC 7.

[0068] Additionally or alternatively, in some embodiments, the controller 5 is configured to control the operation of the switch 4, for example, to control when current is allowed or prevented from flowing between the power supply 6 and the thermistor bridge 10. Additionally or alternatively, the controller 5 is configured to control the operation of the power supply 6, for example, to enable / disable the output of power from the power supply 6 and / or adjust the output of the power supply 6.

[0069] In the illustrated example, controller 5 includes three outputs: digital output 5a, analog output 5b, and logic output 5c. In various examples, controller 5 may include one or more such outputs, but not necessarily all three. In some examples, controller 5 is configured to provide outputs based on information representing the voltage between the first point 11 and the second point 12 of the thermistor bridge 10 (such as, for example, received from ADC 7).

[0070] In some examples, controller 5 communicates with pump 32, which can be configured to cause fluid to flow through a fluid flow system, such as, for example... Figure 1A Pump 102 is configured to flow fluid from reservoir 103 to dispensing point 105. In some examples, pump 32 is configured to cause fluid to flow past a product depletion sensor. In some examples, controller 5 is configured to control the operation of pump 32, such as turning the pump on and off and / or controlling the pump speed. In other examples, controller 5 is configured to receive information from pump 32, such as the operating status of pump 32 (e.g., on / off).

[0071] In various examples, controller 5 may include a general-purpose microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a programmable logic device (PLD), or other equivalent logic device, or a combination of one or more such components. In some examples, the functions attributed to the controller as described herein may be performed by one or more controllers. In some examples, the system may include multiple controllers working in coordination distributed throughout the system.

[0072] In some examples, controller 5 includes or otherwise communicates with memory, which may include instructions (e.g., in a non-transitory computer-readable medium) for causing the controller to perform one or more functions. In some examples, memory includes random access memory (RAM), such as synchronous dynamic random access memory (SDRAM), read-only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), embedded dynamic random access memory (eDRAM), static random access memory (SRAM), flash memory, magnetic or optical data storage media, or a combination of one or more such components.

[0073] In some implementations, it is used to interact with Figure 2 The OOP sensor, which is used in conjunction with various components of the OOP system, includes a housing that defines a flow channel through which the product flows. Figure 3A A side view of an example configuration of an OOP sensor is shown. In the illustrated example, the OOP sensor 300 includes a housing 304 having a first surface 306 and defining a flow channel 308 through which fluid can flow. The sensor 300 includes an inlet 310 and an outlet 312, each inlet and outlet fluidly connecting the flow channel 308 to the outside of the housing 304. In some examples, the inlet 310 and outlet 312 are configured to be coupled to a conduit that can deliver fluid to and from the sensor 300, such that fluid flows from the conduit through the inlet 310, through the flow channel 308, through the outlet 312, and into an additional conduit. Referring to Figure 1, in some examples, the conduit may connect the inlet 310 to a reservoir (e.g., 103), and the additional conduit may connect the outlet 312 to a dispensing location (e.g., 105). In some examples, a pump (e.g., 102) may be positioned between such a reservoir (e.g., 103) and inlet 310 and / or between outlet 312 and such dispensing location (e.g., 105).

[0074] Sensor 300 includes a circuit board 320 coupled to a first surface 306 of housing 304. In some examples, circuit board 320 supports a thermistor bridge, such as... Figure 2The bridge 10 is shown. In some embodiments, fluid flowing through flow channel 308 (e.g., liquid product from a product reservoir) thermally interacts with portions of the thermistor bridge supported by circuit board 320, such that the fluid affects the temperature of one or more thermistors in the thermistor bridge. In some examples, an air gap is provided around the thermistors to prevent heat loss from the thermistors to other structures of the OOP sensor.

[0075] Figure 3B It shows Figure 3A A top view of the OOP sensor. Figure 3B In the example, the OOP sensor 300 includes an inlet 310 and an outlet 312, such as regarding Figure 3A As described. The OOP sensor includes a circuit board 320 supported by a first surface of the housing of the OOP sensor 300. In this example, the circuit board 320 supports a first thermistor 301a, a second thermistor 302b, a third thermistor 302a, and a fourth thermistor 301b. Figure 2 As indicated in the examples, in some embodiments, a first thermistor 301a and a fourth thermistor 301b form a first pair of thermistors 321, and a second thermistor 302b and a third thermistor 302a and a second thermistor 302b form a second pair of thermistors 322. In some embodiments, the first pair of thermistors 321 is positioned in a first sensing region 331, and the second pair of thermistors 322 is positioned in a second sensing region 332. In some such embodiments, the housing 304 is configured such that the thermal resistance between the flow channel of the OOP sensor 300 and the first sensing region 331 is lower than the thermal resistance between the flow channel of the OOP sensor 300 and the second sensing region 332. In some such examples, the fluid flowing in the flow channel of the OOP sensor (e.g., liquid from a product reservoir) will have a greater influence on the temperature of the first pair of thermistors 321 than the second pair of thermistors 322. Furthermore, in some examples, the fluid flowing in flow channel 308 (e.g., a liquid product) will affect the thermal behavior of the first pair of thermistors compared to the absence of fluid (e.g., when only air is present in the flow channel).

[0076] Although Figure 3A and Figure 3B The descriptions shown are top and side views, but such labels are for ease of reference and do not limit the orientation of the OOP sensor 300 that can be used during operation. In some examples, the inlet 310 and outlet 312 are vertically aligned, allowing fluid to flow upward through the flow channel 308. Other orientations are possible.

[0077] Figure 4AAn example cross-sectional view of an implementation of an OOP sensor is shown. Figure 4A The OOP sensor 400 includes a housing 404, a flow channel 408, an inlet 410, and an outlet 412, each inlet and outlet coupling the flow channel 408 to the outside of the housing 404. In some examples, the OOP sensor 400 is configured such that fluid flows in the direction of arrow 490. During example operation, the OOP sensor can be oriented such that arrow 490 points upward and fluid flows vertically upward through the flow channel 408, but operation in other orientations is possible. The housing includes a first surface 406, and the OOP sensor 400 includes a circuit board 420 supported by the first surface of the housing.

[0078] exist Figure 4A In one example, the flow channel 408 includes a bend 409 toward the circuit board 420. The bend 409 may be configured to direct fluid flowing through the flow channel 408 more toward certain portions of the circuit board 420 than others. In some embodiments, the bend 409 in the flow channel 408 directs fluid more toward the first sensing area where the first pair of thermistors are located, compared to the second sensing area where the second pair of thermistors are located.

[0079] Figure 4B It shows Figure 4A An exploded perspective view of the OOP sensor. As shown, the circuit board 420 is configured to join the first surface 406 of the housing 404. In some examples, the thickness of the circuit board is between approximately 0.025 mm and 0.2 mm. In some examples, the circuit board comprises a glass epoxy laminate FR-4 or polyimide.

[0080] The circuit board 420 includes a first pair of thermistors 421 (e.g., including thermistor 401) located in a first sensing region 431 and a second pair of thermistors 422 (e.g., including thermistor 402) located in a second sensing region 432. In an example embodiment, when the circuit board 420 engages a first surface 406 of the housing 404 (e.g., via threaded bolts configured to extend through corresponding holes in the circuit board 420 and engage corresponding threaded holes in the housing 404), the first sensing region 431 is positioned above a bend 409 in the flow channel 408, while the second sensing region 432 is positioned closer to the inlet 410. In some examples, the bend 409 directs fluid flowing in the flow channel 408 toward the first sensing region 431 but not toward the second sensing region 432. Therefore, in some examples, the fluid flowing through the flow channel 408 will have a greater influence on the temperature of the thermistors in the first sensing region 431 than the second sensing region 432.

[0081] For example, Figure 4A A thermistor 401 is shown in a first sensing region above a bend 409 in the flow channel 408, and a thermistor 402 is shown in a second sensing region not above the bend 409. In some embodiments, the bend causes the fluid in the flow channel 408 to move towards the thermistor 401 rather than towards thermistor 402. In some such examples, the temperature of thermistor 401 is more affected by the fluid flowing in the flow channel 408 than the temperature of thermistor 402.

[0082] In some examples, the thermistors (e.g., in the first pair of thermistors 421 and / or the second pair of thermistors 422) are positioned on the inner surface of the circuit board 420 such that the thermistors face inward toward the flow channel. In some examples, a protective layer (such as an acrylic or Teflon film) is placed between the thermistors and the flow channel. In some examples, the thermistors (e.g., in the first pair of thermistors 421 and / or the second pair of thermistors 422) are positioned on the outer surface of the circuit board 420 such that the circuit board 420 is located between the thermistors and the flow channel.

[0083] Figure 4C It shows Figure 4A Another exploded perspective view of the OOP sensor.

[0084] In some examples, the OOP sensor 400 includes a cover 460 configured to be coupled to the OOP sensor housing 404, for example, by one or more bolts (e.g., via threaded bolts configured to extend through corresponding holes in the circuit board 420 and the cover 460 and engage corresponding threaded holes in the housing 404). In some examples, the cover 460 is positioned over the circuit board 420 such that the inner surface of the cover 460 faces the circuit board 420. The inner surface of the cover 460 may include cavities to receive thermistors on the circuit board. In the example of FIG. 4, cavities 441 and 442 may be positioned such that when the cover 460 is positioned over the circuit board 420, a first pair of thermistors 421 is received in cavity 441, and a second pair of thermistors 422 is received in cavity 442. The cavities may provide an air gap around the thermistors to prevent heat loss from the thermistors, for example, by conducting heat to the cover 460 or other components of the OOP sensor 400.

[0085] Figure 5A An example cross-sectional view of an implementation of an OOP sensor is shown. Figure 5AThe OOP sensor 500 includes a housing 504, a flow channel 508, an inlet 510, and an outlet 512, each inlet and outlet coupling the flow channel 508 to the outside of the housing 504. In some examples, the OOP sensor 500 is configured such that fluid flows in the direction of arrow 590. During example operation, the OOP sensor can be oriented such that arrow 590 points upward and fluid flows vertically upward through the flow channel 508, but operation in other orientations is possible. The housing includes a first surface 506, and the OOP sensor 500 includes a circuit board 520 supported by the first surface of the housing.

[0086] exist Figure 5A In one example, the flow channel 508 includes a bend 509 toward the circuit board 520. The bend 509 may be configured to direct fluid flowing through the flow channel 508 more toward certain portions of the circuit board 520 than others. In some embodiments, the bend 509 in the flow channel 508 directs fluid more toward the first sensing area where the first pair of thermistors are located, compared to the second sensing area where the second pair of thermistors are located.

[0087] Figure 5B It shows Figure 5A An exploded perspective view of the OOP sensor. As shown, the circuit board 520 is configured to join the first surface 506 of the housing 504. In some examples, the thickness of the circuit board is between approximately 0.025 mm and 0.2 mm. In some examples, the circuit board comprises a glass epoxy laminate FR-4 or polyimide.

[0088] The OOP sensor 500 includes an insert 550 (e.g., a plastic insert) configured to insert into an aperture 507 in a first surface 506 of a housing 504. In some examples, the insert engages with a portion of a flow channel 508. For example, in some embodiments, the housing 504 defines a first half of a tubular flow channel 508, and the insert 550 includes an inner surface defining a second half of the tubular flow channel. In some such embodiments, when the insert is inserted into the aperture in the first surface 506 of the housing 504, the flow channel defined by the housing 504 and the inner surface of the insert 550 engages to form a closed tubular flow channel.

[0089] The insert 550 shown in the figure includes an aperture 552 extending therethrough. In some examples, when assembling the OOP sensor 500, the aperture 552 provides a fluid path between the flow channel 508 and the circuit board 520.

[0090] The circuit board 520 includes a first pair of thermistors 521 (e.g., including thermistor 501) located in a first sensing region 531 and a second pair of thermistors 522 (e.g., including thermistor 502) located in a second sensing region 532. In an example embodiment, when the circuit board 520 engages a first surface 506 of the housing 504 (e.g., via threaded bolts configured to extend through a corresponding orifice in the circuit board 520 and engage a corresponding threaded hole in the housing 504), the first sensing region 531 is positioned above an orifice 552 in the insert 550, which forms a second half of a flow channel 508 at a bend 509, while the second sensing region 532 is positioned closer to the inlet 510 and is not positioned above the orifice 552. In some examples, the bend 509 directs fluid flowing in the flow channel 508 toward the first sensing region 531 but not toward the second sensing region 532. Additionally or alternatively, the orifice 552 in the insert 550 allows fluid in the flow channel 508 to reach the circuit board 520 at the first sensing region 531, while preventing fluid in the flow channel 508 from reaching the circuit board 520 at the second sensing region 532. Therefore, in some examples, the fluid flowing through the flow channel 508 will have a greater impact on the temperature of the thermistor in the first sensing region 531 compared to the second sensing region 532.

[0091] For example, Figure 5A A thermistor 501 is shown in a first sensing region above an aperture 552 in the insert 550, and a thermistor 502 is shown in a second sensing region not above the aperture 552. In some embodiments, the insert 550 provides thermal insulation between the flow channel 508 and the thermistor 502, but does not provide thermal insulation between the flow channel 508 and the thermistor 501 due to the aperture 552.

[0092] In some examples, a protective layer is positioned between a thermistor in the first sensing region 531 (e.g., in the first pair of thermistors 521 in the first sensing region 531) and the flow channel 508. In some examples, the thermistor is positioned on a first surface of the circuit board 520 such that the circuit board 520 is located between the thermistor and the flow channel 508. In some such examples, the circuit board 520 serves as a protective layer. In other examples, the thermistor is positioned on an inner surface of the circuit board 520 such that the thermistor faces the flow channel 508. In some examples, an acrylic or Teflon protective layer may be positioned above the thermistor to form a protective layer between the thermistor and the flow channel 508.

[0093] Figure 5C It shows Figure 5A Another exploded perspective view of the OOP sensor.

[0094] In some examples, the OOP sensor 500 includes a cover 560 configured to be coupled to the OOP sensor housing 504, for example, by one or more bolts (e.g., via threaded bolts configured to extend through corresponding holes in the circuit board 520 and the cover 560 and engage corresponding threaded holes in the housing 504). In some examples, the cover 560 is positioned over the circuit board 520 such that the inner surface of the cover 560 faces the circuit board 520. The inner surface of the cover 560 may include cavities to receive thermistors on the circuit board. In the example of FIG. 5, cavities 541 and 542 may be positioned such that when the cover 560 is positioned over the circuit board 520, a first pair of thermistors 521 is received in cavity 541, and a second pair of thermistors 522 is received in cavity 542. The cavities may provide an air gap around the thermistors to prevent heat loss from the thermistors, for example, by conducting heat to the cover 560 or other components of the OOP sensor 500.

[0095] Figure 6A An example cross-sectional view of an implementation of an OOP sensor is shown. Figure 6A The OOP sensor 600 includes a housing 604, a flow channel 608, an inlet 610, and an outlet 612, each inlet and outlet coupling the flow channel 608 to the outside of the housing 604. In some examples, the OOP sensor 600 is configured such that fluid flows in the direction of arrow 690. During example operation, the OOP sensor can be oriented such that arrow 690 points upward and fluid flows vertically upward through the flow channel 608, but operation in other orientations is possible. The housing includes a first surface 606, and the OOP sensor 600 includes a circuit board 620 supported by the first surface of the housing. Figure 6A In the example, the flow channel 608 includes a cylindrical flow channel, and the first surface 606 of the housing 604 and the circuit board 620 are curved.

[0096] Figure 6B It shows Figure 6A An exploded perspective view of the OOP sensor. As shown, the circuit board 620 is curved and configured to engage the curved first surface 606 of the housing 604. In some examples, the thickness of the circuit board is between about 0.025 mm and 0.2 mm. In some examples, the circuit board comprises a glass epoxy laminate FR-4 or polyimide. In some examples, the circuit board 620 is not curved when it exists alone, but is flexible, and bends when engaging the curved first surface 606 of the housing 604.

[0097] The OOP sensor 600 includes an aperture 607 in a first surface 606 of a housing 604. In some examples, when the OOP sensor 600 is assembled, the aperture 607 provides a fluid path between a flow channel 608 and a circuit board 620.

[0098] The circuit board 620 includes a first pair of thermistors 621 (e.g., including thermistor 601) located in a first sensing region 631 and a second pair of thermistors 622 (e.g., including thermistor 602) located in a second sensing region 632. In an example embodiment, when the circuit board 620 engages a first surface 606 of the housing 604 (e.g., via threaded bolts configured to extend through a corresponding orifice in the circuit board 620 and engage a corresponding threaded orifice in the housing 604), the first sensing region 631 is positioned above an orifice 607 in the first surface 606 of the housing 604, while the second sensing region 632 is positioned closer to the inlet 610 and not positioned above the orifice 607. In some examples, the orifice 607 allows fluid in the cylindrical flow channel 608 to reach the circuit board 620 at the first sensing region 631 while preventing fluid in the flow channel 608 from reaching the circuit board 620 at the second sensing region 632. Additionally or alternatively, in some embodiments, the curved first surface 606 of the housing 604 further separates the second sensing region 632 from the flow channel 608 compared to the first sensing region 631, and in some examples, the first surface 606 is thicker in the region of the second sensing region 632 than the first sensing region 631, and provides a greater thermal resistance between the second sensing region 632 and the flow channel 608 compared to the thermal resistance between the first sensing region 631 and the flow channel 608. Therefore, in some examples, the fluid flowing through the flow channel 608 will have a greater impact on the temperature of the thermistor in the first sensing region 631 than the fluid flowing through the second sensing region 632.

[0099] For example, Figure 6A A thermistor 601 in a first sensing region and a thermistor 602 in a second sensing region are shown. In some embodiments, a first surface 606 of the housing 604 includes an aperture below the thermistor 601. In some examples, the first surface 606 of the housing 604 provides thermal insulation between the flow channel 608 and the thermistor 602, but not between the flow channel 608 and the thermistor 601 due to the aperture in the first surface 606. Additionally or alternatively, in some examples, the curved first surface is thicker between the thermistor 602 and the flow channel 608 than between the thermistor 601 and the flow channel 608, and provides greater thermal resistance between the flow channel 608 and the thermistor 602 than between the flow channel 608 and the thermistor 601.

[0100] In some examples, a protective layer is positioned between a thermistor (e.g., a first pair of thermistors 621 in the first sensing region 631) and the flow channel 608. In some examples, the thermistor is positioned on a first surface of a circuit board 620 such that the circuit board 620 is positioned between the thermistor and the flow channel 608. In some such examples, the circuit board 620 serves as a protective layer. In other examples, the thermistor is positioned on an inner surface of the circuit board 620 such that the thermistor faces the flow channel 608. In some examples, an acrylic or Teflon protective layer may be positioned over the thermistor to form a protective layer between the thermistor and the flow channel 608.

[0101] Figure 6C It shows Figure 6A Another exploded perspective view of the OOP sensor.

[0102] In some examples, the OOP sensor 600 includes a cover 660 configured to be coupled to the OOP sensor housing 604, for example, by one or more bolts (e.g., via threaded bolts configured to extend through corresponding holes in the circuit board 620 and the cover 660 and engage corresponding threaded holes in the housing 604). In some examples, the cover 660 is positioned over the circuit board 620 such that the inner surface of the cover 660 faces the circuit board 620. The inner surface of the cover 660 may include cavities to receive thermistors on the circuit board. In the example of FIG. 6, cavities 641 and 642 may be positioned such that when the cover 660 is positioned over the circuit board 620, a first pair of thermistors 621 is received in cavity 641, and a second pair of thermistors 622 is received in cavity 642. The cavities may provide an air gap around the thermistors to prevent heat loss from the thermistors, for example, by conducting heat to the cover 660 or other components of the OOP sensor 600.

[0103] Figure 7 An example cross-sectional view of an implementation of an OOP sensor is shown. Figure 7 The OOP sensor 700 includes a housing 704, a flow channel 708, an inlet 710, and an outlet 712, each inlet and outlet coupling the flow channel 708 to the outside of the housing 704. In some examples, the OOP sensor 700 is configured such that fluid flows in the direction of arrow 790. During example operation, the OOP sensor can be oriented such that arrow 790 points upward and fluid flows vertically upward through the flow channel 708, but operation in other orientations is possible. The housing includes a first surface 706, and the OOP sensor 700 includes a circuit board 720 supported by the first surface of the housing. Figure 7In the example, the flow channel 708 includes a cylindrical flow channel, and the first surface 706 of the housing 704 and the circuit board 720 are curved.

[0104] As shown in the figure, the circuit board 720 is curved and configured to engage the curved first surface 706 of the housing 704. In some examples, the thickness of the circuit board is between about 0.025 mm and 0.2 mm. In some examples, the circuit board comprises a glass epoxy laminate FR-4 or polyimide. In some examples, the circuit board 720 is not curved when it exists alone, but is flexible, and bends when engaging the curved first surface 706 of the housing 704.

[0105] In some embodiments, the circuit board 720 includes a first pair of thermistors (e.g., including thermistor 701) located in a first sensing region 731 and a second pair of thermistors (e.g., including thermistor 702) located in a second sensing region 732. Figure 7 In the illustrated examples, the first surface 706 of the housing 704 is thicker between the cylindrical flow channel 708 and the second sensing region 732 than between the cylindrical flow channel 708 and the first sensing region 731. In some such examples, the thicker first surface 706 of the housing 704 provides greater thermal resistance between the flow channel and the corresponding sensing region. Therefore, in some examples, the fluid flowing through the flow channel 708 will have a greater impact on the temperature of the thermistor in the first sensing region 731 than the second sensing region 732. In some examples, the housing 704 forms a fully closed flow channel 708 with a first surface 706 having regions of different thicknesses to provide varying degrees of thermal insulation between the flow channel 708 and the sensing region of the first surface 706 opposite to the flow channel 708. In some examples, closing the flow channel 708 with the first surface 706 of the housing 704 can protect the circuit board 720 and / or components on it (e.g., one or more thermistors) from the effects of fluids flowing in the flow channel 708, such as corrosive fluids that may damage such components.

[0106] In some examples, the OOP sensor 700 includes a cover 760 configured to be coupled to the OOP sensor housing 704, for example, by one or more bolts (e.g., via threaded bolts configured to extend through corresponding holes in the circuit board 720 and the cover 760 and engage corresponding threaded holes in the housing 704). In some examples, the cover 760 is positioned above the circuit board 720 such that the inner surface of the cover 760 faces the circuit board 720. The inner surface of the cover 760 may include a cavity to accommodate a thermistor on the circuit board. Figure 7In the example, cavities 741 and 742 can be positioned such that when the cover 760 is placed over the circuit board 720, thermistor 701 is received in cavity 741, and thermistor 702 is received in cavity 742. The cavities may provide an air gap around the thermistors to prevent heat loss from the thermistors, for example, by conducting heat to the cover 760 or other components of the OOP sensor 700.

[0107] As described, in various examples, the OOP sensor may include at least a first sensing region and a second sensing region, and may be configured such that the thermal resistance between the flow channel and the first sensing region is lower than the thermal resistance between the flow channel and the second sensing region, and / or the fluid flowing in the flow channel is directed more towards the first sensing region than the second sensing region. In some examples, bends in the flow channel may direct the fluid towards the first sensing region, for example, as... Figure 4A As illustrated in the implementation scheme. Additionally or alternatively, in some examples, the OOP sensor may include an obstruction in the flow channel configured to alter the flow of fluid through the channel and direct the fluid in the flow channel toward a sensing area (e.g., a first sensing area).

[0108] Figure 8 An example OOP sensor is shown. Figure 8 The OOP sensor 800 includes a housing 804, a flow channel 808, an inlet 810, and an outlet 812, each inlet and outlet coupling the flow channel 808 to the outside of the housing 804. In some examples, the OOP sensor 800 is configured such that fluid flows in the direction of arrow 890. During example operation, the OOP sensor can be oriented such that arrow 890 points upward and fluid flows vertically upward through the flow channel 808, but operation in other orientations is possible. Figure 8 The OOP sensor includes an obstacle 809 positioned within a flow channel 808 that can alter the flow of fluid through the flow channel 808. Figure 8 The obstacle 809 includes a U-shaped wall, but other shapes of obstacles are also possible. In some examples, the obstacle (e.g., 809) may be configured to guide fluid flowing in the flow channel (e.g., 808) toward the first sensing area rather than toward the second sensing area.

[0109] While the illustrated examples include arrows indicating the direction of flow (e.g., 490, 590, 690, 790, 890), in some examples, the OOP sensors shown and described herein can operate when fluid flows through the sensor in either direction. For example, in some examples, although described as including an inlet and an outlet coupled to a flow channel, various OOP sensors can be configured to receive fluid at either inlet or outlet, such that fluid flows from one inlet or outlet to the other. In some embodiments, the OOP sensor is symmetrical, such that when fluid is configured to flow through the OOP in either direction, similar measurements can be used to detect the presence or absence of fluid in the OOP sensor.

[0110] As described, in some examples, the OOP sensor may be configured such that fluid flowing through its flow channel (e.g., liquid product from a product reservoir) will have a greater effect on the temperature of the thermistor in the first sensing region than the thermistor in the second sensing region, for example, due to the lower thermal resistance between the flow channel and the first sensing region compared to the flow channel between the second sensing region, and / or directing the fluid toward the first sensing region rather than the second sensing region.

[0111] Figure 2 An example connection between thermistors 1a, 1b, 2a, 2b and power supply 6 is illustrated. Typically, when using a thermistor to measure temperature, the current flowing through the thermistor is regulated to limit power dissipation within the thermistor. The thermistor changes its resistance in response to temperature changes. In this case, the resistance reflects the ambient temperature.

[0112] In some examples of operating an OOP sensor according to this disclosure, a high-current pulse is briefly applied to the thermistor, causing a transient change in the thermistor's temperature. In some embodiments, this temperature change may exceed 20°C, and in some cases, reach or exceed 100°C.

[0113] In the example implementation, the thermistors 1a, 1b, 2a, and 2b used in the OOP sensor are NTC thermistors, which introduce positive feedback over time. When a constant voltage V is applied to the NTC thermistors, the power dissipation P initially increases from P0 = V. 2 / R t0 Beginning, where R t0 This indicates the initial resistance. Nevertheless, as the temperature rises, the resistance of the thermistor decreases, causing the current to gradually increase over time unless the applied voltage is reduced or the circuit is closed. A constant resistor (e.g., a current-limiting resistor 3) connected in series with the thermistor protects the thermistor from potential damage.

[0114] like Figure 2 As depicted in the circuit diagram, thermistors 1a, 1b, 2a, and 2b are arranged in bridge 10, and current-limiting resistor 3 is connected in series. The selection of the nominal resistance values ​​of the thermistors, current-limiting resistor, and applied voltage is strategic, allowing for rapid self-heating without jeopardizing the thermistors. In the proposed configuration, self-heating (e.g., applying voltage from power supply 6) similarly raises the temperature of all thermistors. This temperature uniformity is achieved through a short preheating duration and a more gradual heat transfer characteristic.

[0115] Therefore, the thermistors exhibit similar temperatures during the self-heating process. Once the voltage is deactivated, the temperature of the thermistor begins to decrease as heat dissipates into the surrounding environment. The rate of heat transfer can vary when different materials approach the thermistor, allowing differentiation between fluids and air. As described elsewhere in this document, short voltage pulses applied to the thermistor bridge can be used to allow signals to be read from one or more thermistors without heating them. As the temperature of one or more thermistors in the thermistor bridge 10 changes, the resulting change in thermistor resistance can lead to, for example, different signals received at ADC 7.

[0116] As described elsewhere in this document, in some examples, thermistors 1a and 1b form a first pair of thermistors, and thermistors 2a and 2b form a second pair of thermistors. In some examples, the first pair of thermistors is positioned in a first sensing region, while the second pair of thermistors is positioned in a second sensing region, wherein the first sensing region makes its thermistor temperature more susceptible to the influence of the fluid flowing in the flow channel of the OOP sensor. In example embodiments, each of thermistors 1a, 1b, 2a, and 2b has the same resistance-to-temperature relationship. In this example, if all thermistors have the same temperature and the same resistance, the voltage drop across thermistors 1a and 2a will be the same, and the voltage difference between points 11 and 12 will be zero. If thermistors 1a and 1b are at the same temperature, and thermistors 2a and 2b are at the same temperature, and thermistors 1a and 1b have a lower resistance than thermistors 2a and 2b (e.g., due to the temperature effect of the fluid in the flow channel), then thermistor 1a will drop less voltage than thermistor 2a, and the voltage difference between point 11 and point 12 will be non-zero. Therefore, in some examples, the temperature deviation between the first sensing area and the second sensing area can cause a voltage difference between point 11 and point 12 (such as in…) Figure 2The change in voltage difference is measured at input 7a of ADC 7. In some examples, the signal at input 7b (representing the voltage drop across the thermistor 2b) represents the general temperature level of the thermistor in the second sensing region.

[0117] During the example operation, the controller (e.g., Figure 2 The controller 5 in the middle can be configured to work with multiple thermistors (e.g., Figure 2 The interactions of 1a, 1b, 2a, and 2b in the OOP sensor are used to detect the presence of a product in the flow channel. (Reference) Figure 2 In an example implementation, controller 5 is configured to place switch 4 in an ON state to allow current to flow from power supply 6 to the thermistor bridge 10 to heat one or more thermistors of the thermistor bridge 10. Figure 2 In the example, current from power supply 6 flows through both the first and second branches of the thermistor bridge to reach the reference potential. In some examples, the current through the thermistor causes the thermistor's temperature to rise. The fluid flowing through the flow channels of the OOP sensor can affect the thermistor's temperature differently; for example, it may affect the thermistor in the first sensing region more than the thermistor in the second sensing region.

[0118] In some examples, the controller is configured to place the switch in the ON state to allow current to flow from the power supply to the thermistor bridge for a heating duration. In some examples, the heating duration is between 1 ms and 1000 ms. In some examples, the controller 5 is configured to place the switch 4 in the OFF state to stop current flow to the thermistor bridge 10 and maintain the switch in the OFF state for a delay duration. In some examples, the delay duration is between 1 ms and 1000 ms. After the delay duration and during the reading duration, the controller 5 is configured to provide multiple measurement pulses to the thermistor bridge 10, for example, by switching the switch 4 between the OFF and ON states. In some embodiments, the reading duration is between 10 ms and 2000 ms. In some examples, each measurement pulse has a measurement pulse duration between 0.1 ms and 5 ms (e.g., the time the switch is in the ON state) and is provided at a measurement frequency between 10 Hz and 100 Hz. For example, in some examples, the time between the rising edges of consecutive pulses is between 10 ms and 100 ms.

[0119] Figure 9 This is an example voltage-time graph showing the voltage output from switch 4. For example, in some examples, power supply 6 is configured to output 5VDC, and the switch controls whether 5VDC is output from the switch. In the illustrated example, controller 5 controls switch 4 to output 5VDC at excitation time t.E During this period, power is supplied to the thermistor bridge 10, and the power supply is stopped for a duration of time t. D , so as to read at time t R A series of excitation pulses are provided during the period, each measurement pulse having a reading pulse time t. p The rising edge of each pulse is determined by the measurement period t. m Separately. After a series of measurement pulses during the reading time, controller 5 can cause switch 4 to stop supplying power to the thermistor bridge 10 for a duration normalized time t. N During the normalization time, the thermistor can return to its equilibrium temperature. In some examples, the excitation time, delay time, reading time, and normalization time are combined to form a measurement cycle. In some examples, the measurement cycle can be repeated over time.

[0120] In some examples, the excitation time can be between 1 ms and 1000 ms, the delay time can be between 1 ms and 1000 ms, the reading time can be between 10 ms and 2000 ms, the normalization time can be between 10 ms and 10,000 ms, the reading pulse can be between 0.1 ms and 5 ms, and the measurement period can be between 5 ms and 200 ms. In various implementations, one or more of these times can be adjustable.

[0121] Figure 11 An example current pulse through a thermistor bridge is shown for an example implementation. Figure 12 Example readings measured at input 7a and example corresponding flow state indications based on these readings are shown.

[0122] The controller 5 can be configured to receive a measurement signal value during each of a plurality of measurement pulses. In some examples, the measurement signal value represents the voltage between points 11 and 12 of the thermistor bridge 10. In some examples, the measurement signal value is the output of the ADC 7 communicating with points 11 and 12. In some examples, the measurement signal is a voltage. In some examples, the measurement signal corresponds to the temperature difference between thermistors in a first sensing region and a second sensing region.

[0123] In some implementations, the measurement pulse is short enough not to significantly change the temperature of the thermistor, but long enough to determine the measurement signal value during the measurement pulse. In some examples, the current-limiting resistor 3 suppresses the current flowing through the thermistor during the measurement pulse to prevent heating of the thermistor. Additionally or alternatively, in some examples, the current-limiting resistor 3 suppresses the current flowing through the thermistor during the heating duration to prevent damage to the thermistor. In some examples, the power supply 6 provides a 5VDC output. In some examples, the current-limiting resistor is between approximately 10 ohms and 100 ohms. In some examples, the resistance of the thermistor varies between approximately 30 ohms and 100 ohms over a range of operating temperatures.

[0124] In some implementations, controller 5 is further configured to receive a second signal representing the voltage drop across a thermistor (e.g., a signal related to the voltage drop across the thermistor 1b received as a second input 7b of ADC 7). In some examples, the second signal provides an indication of the temperature of the thermistor in the first sensing region. In some examples, the temperature of such a thermistor can be used for temperature correction of the measured signal value. Therefore, in some examples, a measurement pulse is used to receive a signal based on... Figure 2 The controller 5 can receive a second signal representing the voltage drop between points 11 and 12 in the second sensing area, and can be configured to receive a second signal representing the voltage drop across the thermistor 2b. The controller 5 can use the second signal representing the temperature of the second sensing area to determine a correction measurement signal value. For example, correction (e.g., polynomial correction) can be used to compensate for hot or cold fluid flowing through the OOP sensor.

[0125] Figure 13 Example graphs showing the variation of measured signals with temperature under various flow conditions are shown. Figure 13 The example first signal X7a occurring at different temperatures for different OOPs is shown (e.g., from...). Figure 2 The different contours of the measurement signal generated by the input 7a of the ADC 7. Temperature variations in the first signal X7a can be mitigated by applying a multiplication of X7a with an adjustable correction coefficient. In some examples, the correction coefficient can be constructed as the second signal X7b (e.g., Figure 2 The fourth-order polynomial of the input 7b) of ADC 7. For example, in the example implementation, the correction signal X7a_corr can be calculated for each measurement using the following equation:

[0126] X7a_corr = X7a (1 +(X7b0 -X7b) (A + (X7b0 -X7b) (B +(X7b0 -X7b) (C +D (X7b0 -X7b)))))

[0127] Where X 7a and X 7b These are the first and second signals currently being measured, and X 7b0 A, B, C, and D are constants recorded in the controller's memory. In some cases, these constants can be calculated during factory calibration.

[0128] In some examples, this temperature correction mechanism effectively addresses situations involving fluids passing through the sensor at different temperatures, such as... Figure 14 The diagram depicts example graphs of raw and calibrated sensor readings at constant flow rates over different temperature ranges. Similarly, its effectiveness extends to capturing OOP events under varying temperature conditions, such as... Figure 15 The example illustrates the calibrated sensor readings for different flow states within different temperature ranges.

[0129] Although Figures 11 to 15 The graphs in the diagram include units on both the horizontal and vertical axes, but such graphs illustrate example operation according to some implementation schemes. Other values ​​(such as other current, voltage, and time scales) are possible.

[0130] Other temperature measurement and / or calibration techniques are possible. In some implementations, a separate thermistor can be used to measure temperature. Figure 16 An alternative exemplary schematic diagram is shown, illustrating various aspects of a product depletion sensing system including an independent thermistor. Similar to... Figure 2 Example, Figure 16The example illustrates a thermistor bridge 10 comprising a plurality of thermistors, including a first thermistor 1a, a second thermistor 2b, a third thermistor 2a, and a fourth thermistor 1b. In the illustrated example, the thermistor bridge 10 includes a first branch comprising the first thermistor 1a connected in series with the second thermistor 2b, wherein a first point 11 is located between the first thermistor 1a and the second thermistor 2b. The thermistor bridge 10 also includes a second branch comprising the third thermistor 2a connected in series with the fourth thermistor 1b, wherein a second point 12 is located between the third thermistor 2a and the fourth thermistor 1b. In some examples, as described elsewhere herein, the first thermistor 1a and the fourth thermistor 1b form a first pair of thermistors 21, and the second thermistor 2b and the third thermistor 2a form a second pair of thermistors 22. The first and second branches are connected in parallel between the power supply side 15 and the reference side 16 of the thermistor bridge 10. In the illustrated example, the first thermistor 1a and the third thermistor 2a are coupled to the power supply side 15 of the thermistor bridge 10, and the second thermistor 2b and the fourth thermistor 1b are coupled to the reference side 16 of the thermistor bridge 10.

[0131] Figure 16 The components can be related to... Figure 2 The components with the same number described operate in a similar manner. Power supply 6 can provide power to the power supply side 15 of the thermistor bridge 10 via switch 4 controlled by controller 5. Resistor 3 can limit the current supplied to the thermistor bridge 10. The first input 7a of ADC 7 can be configured to receive a signal representing the voltage difference between the first point 11 and the second point 12, which can provide information about the temperature deviation between the first and second sensing areas of the OOP sensor.

[0132] exist Figure 16 In the example, the independent thermistor 8 receives power from the power supply 6 via a load resistor 9 connected in series with the independent thermistor 8. The independent thermistor 8 may be supported by a circuit board in a location near the thermistor bridge 10. In the illustrated example, the load resistor 9 receives a constant voltage from the power supply 6. In some embodiments, the load resistor 9 and the independent thermistor 8 have high resistance to reduce the load current generated by the voltage from the power supply 6 and to reduce self-heating. For example, in some embodiments, the nominal resistance of the thermistor and the load resistor may be selected from between about 10kΩ and 100kΩ.

[0133] In the illustrated example, load resistor 9 and independent thermistor 8 are connected in series between power supply 6 and reference potential 25. If the temperature (and therefore the resistance) of independent thermistor 8 changes, the amount of voltage drop from power supply 6 due to independent thermistor 8 also changes. Therefore, the voltage drop due to independent thermistor 8 is a function of the temperature of independent thermistor.

[0134] exist Figure 16 In the example, instead of such Figure 2 The ADC receives a signal representing the voltage drop across the thermistor 2b, and the second input 7b of the ADC is configured to receive a signal representing the voltage drop across the independent thermistor 8, which corresponds to the temperature of the independent thermistor 8.

[0135] In an example implementation, controller 5 is configured to receive input from the ADC based on the signal at the second input 7b of the ADC, and can be configured to determine the temperature of the independent thermistor 8 based on the received input. In some implementations, the temperature can be calculated based on a measured voltage at the second input 7b corresponding to the voltage across the independent thermistor 8. In the example implementation, the temperature is calculated using a second-order polynomial fit as a function of voltage, where the thermistor temperature T = AV. 2 +BV+C, where A, B, and C are constants, and V is the voltage across the independent thermistor 8 at the second input 7b. The constants A, B, and C can be determined empirically. In one example, A = 1.27 × 10⁻⁶. -6 B = -6.32 × 10 -2 C=78.6.

[0136] Figure 17A An example cross-sectional view of an implementation of an OOP sensor that includes a separate thermistor in addition to the thermistor bridge is shown. Figure 17A The OOP sensor 1700 includes a housing 1704, a flow channel 1708, an inlet 1710, and an outlet 1712, each inlet and outlet coupling the flow channel 1708 to the outside of the housing 1704. In some examples, the OOP sensor 1700 is configured such that fluid flows in the direction of arrow 1790. During example operation, the OOP sensor can be oriented such that arrow 1790 points upward and fluid flows vertically upward through the flow channel 1708, but operation in other orientations is possible. The housing includes a first surface 1706, and the OOP sensor 1700 includes a circuit board 1720 supported by the first surface of the housing.

[0137] exist Figure 17AIn one example, the flow channel 1708 includes a bend 1709 toward the circuit board 1720. The bend 1709 may be configured to direct fluid flowing through the flow channel 1708 toward certain portions of the circuit board 1720 rather than others. In some embodiments, the bend 1709 in the flow channel 1708 directs fluid toward the first sensing area where the first pair of thermistors is located, rather than toward the second sensing area where the second pair of thermistors is located.

[0138] Figure 17B It shows Figure 17A An exploded perspective view of the OOP sensor. As shown, the circuit board 1720 is configured to join the first surface 1706 of the housing 1704. In some examples, the thickness of the circuit board is between approximately 0.025 mm and 0.2 mm. In some examples, the circuit board comprises a glass epoxy laminate FR-4 or polyimide.

[0139] The OOP sensor 1700 includes an insert 1750 (e.g., a plastic insert) configured to be inserted into an aperture 1707 in a first surface 1706 of a housing 1704. In some examples, the insert engages with a portion of a flow channel 1708. For example, in some embodiments, the housing 1704 defines a first half of a tubular flow channel 1708, and the insert 1750 includes an inner surface defining a second half of the tubular flow channel. In some such embodiments, when the insert is inserted into the aperture in the first surface 1706 of the housing 1704, the flow channel defined by the housing 1704 and the inner surface of the insert 1750 engages to form a closed tubular flow channel.

[0140] The insert 1750 shown in the figure includes an aperture 1752 extending therethrough. In some examples, when assembling the OOP sensor 1700, the aperture 1752 provides a fluid path between the flow channel 1708 and the circuit board 1720.

[0141] The circuit board 1720 includes a first pair of thermistors 1721 (e.g., including thermistor 1701) located in a first sensing region 1731 and a second pair of thermistors 1722 (e.g., including thermistor 1702) located in a second sensing region 1732. In an example embodiment, when the circuit board 1720 engages a first surface 1706 of the housing 1704 (e.g., via threaded bolts configured to extend through a corresponding orifice in the circuit board 1720 and engage a corresponding threaded hole in the housing 1704), the first sensing region 1731 is positioned above an orifice 1752 in the insert 1750, which forms a second half of a flow channel 1708 at a bend 1709, while the second sensing region 1732 is positioned closer to the inlet 1710 and is not positioned above the orifice 1752. In some examples, the bend 1709 directs fluid flowing in the flow channel 1708 toward the first sensing region 1731, but not toward the second sensing region 1732. Additionally or alternatively, the orifice 1752 in the insert 1750 allows fluid in the flow channel 1708 to reach the circuit board 1720 at the first sensing region 1731, while preventing fluid in the flow channel 1708 from reaching the circuit board 1720 at the second sensing region 1732. Therefore, in some examples, the fluid flowing through the flow channel 1708 will have a greater impact on the temperature of the thermistor in the first sensing region 1731 than the thermistor in the second sensing region 1732.

[0142] For example, Figure 17A A thermistor 1701 is shown in a first sensing region above an orifice 1752 in the insert 1750, and a thermistor 1702 is shown in a second sensing region not above the orifice 1752. In some embodiments, the insert 1750 provides thermal insulation between the flow channel 1708 and the thermistor 1702, but does not provide thermal insulation between the flow channel 1708 and the thermistor 1701 due to the orifice 1752.

[0143] In some examples, a protective layer is positioned between a thermistor in the first sensing region 1731 (e.g., in the first pair of thermistors 1721 in the first sensing region 1731) and the flow channel 1708. In some examples, the thermistor is positioned on a first surface of a circuit board 1720 such that the circuit board 1720 is located between the thermistor and the flow channel 1708. In some such examples, the circuit board 1720 serves as a protective layer. In other examples, the thermistor is positioned on an inner surface of the circuit board 1720 such that the thermistor faces the flow channel 1708. In some examples, an acrylic or Teflon protective layer may be positioned over the thermistor to form a protective layer between the thermistor and the flow channel 1708.

[0144] Figure 17C It shows Figure 17A Another exploded perspective view of the OOP sensor.

[0145] In some examples, the OOP sensor 1700 includes a cover 1760 configured to be coupled to the OOP sensor housing 1704, for example, by one or more bolts (e.g., via threaded bolts configured to extend through corresponding holes in the circuit board 1720 and the cover 1760 and engage corresponding threaded holes in the housing 1704). In some examples, the cover 1760 is positioned over the circuit board 1720 such that the inner surface of the cover 1760 faces the circuit board 1720. The inner surface of the cover 1760 may include cavities to receive thermistors on the circuit board. In the example of FIG. 17, cavities 1741 and 1742 may be positioned such that when the cover 1760 is positioned over the circuit board 1720, a first pair of thermistors 1721 is received in cavity 1741, and a second pair of thermistors 1722 is received in cavity 1742. The cavity can provide an air gap around the thermistor to prevent heat loss from the thermistor, for example, by conducting heat to other components of the cover 1760 or OOP sensor 1700.

[0146] The OOP sensor 1700 also includes an independent thermistor 1703 located on a circuit board 1720. This independent thermistor is on the same side as the first pair of thermistors 1721 and the second pair of thermistors 1722 and is located in a third sensing area 1733. A cavity 1743 in the cover 1760 can receive the independent thermistor 1703 when the cover 1760 is placed over the circuit board 1720 and provides an air gap around the independent thermistor 1703. The independent thermistor 1703 may be similar to Figure 16 The independent thermistor 8 in the middle is electrically configured.

[0147] An orifice 1752 in the cover 1750 extends such that at least a portion of the third sensing region 1733 is exposed to fluid flowing through the flow channel 1708 via the orifice to allow thermal contact between the fluid and the third sensing region. In some such examples, a separate thermistor 1703 may be used to sense the temperature of the fluid.

[0148] In some implementations, the OOP sensor 1700 includes a heat sink 1719 positioned near the second pair of thermistors 1722, such that the heat sink 1719 affects the thermal behavior of the second pair of thermistors 1722. Figure 17DAn example heat sink is shown near a pair of thermistors. In some examples, heat sink 1719 is placed on top of a second pair of thermistors 1722. Heat sink 1719 stabilizes the temperature of the second pair of thermistors 1722. The heat sink may comprise metal foil (e.g., copper or stainless steel), and in various embodiments, the thickness of the metal foil may be from 0.05 mm to 0.3 mm and have dimensions from 1 × 2 mm to 5 × 5 mm. In some cases, the presence of heat sink 1719 increases the difference in the measured signal between the state corresponding to the flow of fluid through flow channel 1708 and the state corresponding to the presence of air and the absence of fluid in flow channel 1708, compared to other similar designs without a heat sink.

[0149] Figures 17A to 7 C illustrates an example OOP sensor 1700, which has some features similar to OOP sensor 500, including a flow channel with a bend and an insert with an orifice. Figures 17A to 17D One or more features of the OOP sensor 1700 (such as independent thermistors and corresponding structures and / or heat sinks near the second pair of thermistors) may be included in the various OOP sensor designs described herein.

[0150] As described elsewhere herein, in some implementations, temperature information (e.g., received at input 7b of ADC 7) can be used to correct the value of the measured signal (e.g., received at input 7a of ADC 7). The temperature information can be obtained using a thermistor (e.g., as part of a thermistor bridge) that is part of a thermistor bridge. Figure 2 (as shown) or use a separate thermistor (e.g., as shown) Figure 16 (As shown) to determine.

[0151] In some examples, the controller can be configured to perform polynomial correction of the thermistor bridge readings based on the measured temperature. In an example implementation, the normalized measured signal voltage can be calculated as:

[0152]

[0153] Where V 流动 (T) = A1 × T 4 + A2 × T 3 + A3 × T 2 + A4 × T + A5, V 测量(t) is the raw measurement signal from the thermistor bridge, where the values ​​of A1, A2, A3, A4, and A5 can be determined by least-squares polynomial fitting of the bridge readings to temperature while the fluid flows constantly through the OOP sensor. In one example: A1 = -1.41 × 10 -4 A2 = 1.86 × 10 -2 A3 = -8.89×10 -1 A4 = 20.82, A5 = -380.

[0154] In another example, the controller can calculate the time derivative of the temperature measurement and use this time derivative to correct the bridge measurement signal based on the temperature. In the example implementation, the time derivative of the temperature is calculated as follows:

[0155]

[0156] The value 'a' can be chosen empirically to minimize noise. In one example, a = 50, such that the time derivative of the temperature at a given point is equal to the temperature change over 50 data points. The time derivative T' can be used to determine the correction factor A(Tʹ). In one example, V 校正 (t, Tʹ) = V 归一化 ( t ) × A(Tʹ), where A(Tʹ) = C1× Tʹ + C2.

[0157] Constants C1 and C2 can be chosen empirically to optimize the signal-to-noise ratio, and in some cases, C2 can be fixed at a predetermined value (e.g., C2 = 1) and C1 can be determined. In an example implementation, C2 = 1 and C1 = 0.16. In various examples, C1 is between 0.04 and 0.2. In some implementations, a similar correction may be additionally or alternatively applied to the original measurement signal V. 测量 (t). In some such examples, with the corrected normalized signal V 归一化 Compared to (t), different constants are used to optimize the correction of the measurement signal.

[0158] In addition to temperature correction of the measurement signal (e.g., using temperature to adjust the measurement signal measured at the thermistor bridge) or as an alternative, other system adjustments can be made to compensate for temperature effects. For example, in some examples, the frequency of the measurement pulse (and...) Figure 9 The measurement period t in m (Inversely proportional) to the measurement signal, which is related to the voltage measured at the thermistor bridge.

[0159] Figure 18AAn example graph showing the measurement signal as a function of measurement frequency during a constant fluid flow through an OOP sensor is shown. As illustrated, in the example, the measurement signal decreases as the measurement frequency increases. Figure 18B An example graph showing the relationship between the measurement frequency required to maintain a constant measurement signal and temperature is presented. As shown in the figure, the measurement frequency required to maintain the measurement signal value increases with increasing temperature. Furthermore, as... Figure 13 As shown, in some cases, the measurement signal increases with temperature. Therefore, in some implementations, the measurement frequency can be adjusted based on temperature so that the effects of temperature and frequency on the measurement signal are at least partially canceled out.

[0160] The measurement frequency can be determined based on the measurement temperature (e.g., the temperature measured at the thermistors of a thermistor bridge or the temperature measured using a separate thermistor). In some examples, the measurement frequency increases linearly with temperature. In other examples, other functional relationships, such as power-law relationships, may be used. Other mappings from temperature to measurement frequency are possible, such as lookup tables or other relationships.

[0161] Figure 19 An example measurement signal is shown for a constant fluid flow through an OOP sensor, at a constant measurement frequency and a measurement frequency that varies linearly with temperature. Figure 19 The measurement signal 1900 at different temperatures using a constant measurement frequency is shown, along with the fitted line 1902 for that measurement signal. Figure 19 Measurement signals 1910 at different temperatures using a measurement frequency that increases linearly with temperature, and a fitted line 1912 for such measurement signals are also shown. As shown, the measurement signal 1910 generated by a measurement frequency that increases with temperature is more constant over the illustrated temperature range at a given flow rate, compared to the measurement signal 1900 generated by a constant measurement frequency.

[0162] In some examples, the relationship between measurement frequency and temperature (whether via a lookup table or a fitted equation) can be defined empirically during calibration. In some cases, the relationship between measurement frequency and temperature can be calibrated for a given system before use.

[0163] In some examples, controller 5 is configured to determine an average measurement signal value based on measurement signal values ​​received during the reading duration, for example, by averaging the measurement signal values ​​associated with each of a plurality of measurement pulses during the reading duration. In some embodiments, the controller is configured to determine an average measurement signal value for each measurement cycle, for example, as... Figure 9 As shown. In some examples, the controller is configured to determine the flow state through the flow channel based on the average measured signal value.

[0164] In some embodiments, determining the flow state through a flow channel includes comparing an average measured signal value with one or more predetermined threshold conditions. In some examples, determining the flow state includes determining that fluid is flowing in the flow channel if the average measured signal value meets a first predetermined threshold condition (e.g., below a predetermined threshold). Additionally or alternatively, in some examples, determining the flow state includes determining that fluid is not present in the flow channel if the average measured signal value meets a second predetermined threshold condition (e.g., above a second predetermined threshold). In some further embodiments, determining the flow state within the flow channel also includes determining that fluid is present in the flow channel but is not flowing if the average measured signal value is between the first predetermined threshold and the second predetermined threshold.

[0165] In some examples, the thermistor is a negative temperature coefficient (NTC) thermistor, meaning its resistance decreases as temperature increases. (Reference) Figure 2 and Figure 9 If thermistors 1a and 1b are more affected by the fluid in the flow channel in the first sensing region than thermistors 2a and 2b in the second sensing region, then during the excitation time ( Figure 9 t in E During this period, the thermistor is heated and allowed to [operate / operate] at [temperature]. Figure 9 The delay time (t) D After a period of rest, thermistors 1a and 1b are cooled more by the fluid in the flow channel than thermistors 2a and 2b because their temperature is significantly lower. If thermistors 1a and 1b are colder than thermistors 2a and 2b, and these thermistors are NTC thermistors, then the resistance of thermistors 1a and 1b will be higher than that of thermistors 2a and 2b. In some such examples, the voltage drop across thermistor 1a will be greater than that across thermistor 2a, and the voltage at point 11 will be higher than that at point 12. In some examples, the greater the temperature difference between thermistors 1a, 1b and thermistors 2a, 2b, the greater the voltage difference at points 11 and 12. In some examples, the higher voltage at point 11 compared to the voltage at point 12 results in a negative voltage at the first input 7a of ADC 7. In some cases, the more lower the temperature of thermistors 1a and 1b is compared to the temperature of thermistors 2a and 2b, the more negative the voltage at the first input 7a of ADC 7 becomes.

[0166] Figure 10 An example graph of the average measured signal value over time is shown. In the illustrated example, the graph shows the voltage changing over time (e.g., in mV to seconds), but other data, such as temperature information, are also possible. Figure 10 In the example, the graph illustrates a first predetermined threshold of 1000 and a second predetermined threshold of 1010. As described elsewhere herein, in some embodiments, if the average measured signal value meets a first predetermined threshold condition, the controller determines that fluid (e.g., liquid from a product reservoir) is flowing in the flow channel, and if the average measured signal value meets a second predetermined threshold condition, the controller determines that fluid (e.g., liquid from a product reservoir) is not present in the flow channel. Reference Figure 10 In some examples, the average measurement signal value that satisfies the first predetermined threshold condition includes an average measurement signal value that is lower than the first predetermined threshold 1000. In some examples, the average measurement signal value that satisfies the second predetermined threshold condition includes an average measurement signal value that is higher than the second predetermined threshold 1010, which is higher than the first predetermined threshold.

[0167] For example, in some examples, as described herein, the thermistor includes an NTC thermistor, and the fluid in the flow channel can cause the thermistor in the first sensing region to have a lower temperature and higher resistance compared to the thermistor in the second sensing region, thereby causing a negative voltage sensed at ADC 7. In some examples, the flowing fluid lowers the temperature of the thermistor in the first sensing region faster and / or to a greater extent than stagnant fluid present in the flow channel but not flowing. However, stagnant fluid can still lower the temperature of the thermistor in the first sensing region faster and / or to a greater extent than the thermistor in the second sensing region. Therefore, in some examples, determining the flow state within the flow channel also includes determining that fluid is present in the flow channel but not flowing if the average measured signal value is between a first predetermined threshold 1000 and a second predetermined threshold 1010.

[0168] refer to Figure 10 In some examples, data points representing average measurements below a first predetermined threshold 1000 correspond to time points when fluid is flowing in the flow channel. Data points representing average measurements above a second predetermined threshold 1010 correspond to time points when fluid is not present in the flow channel. Data points representing average measurements between the first predetermined threshold 1000 and the second predetermined threshold 1010 correspond to time points when fluid is present in the flow channel but is not flowing.

[0169] In some examples, fluid corresponds to liquid, such as from a product reservoir, such that fluid present and / or flowing in the flow channel corresponds to liquid in the flow channel, and fluid not present in the flow channel corresponds to liquid not present in the flow channel. For example, in some cases, the absence of liquid corresponds to the presence of only air in the flow channel without liquid.

[0170] In some examples, the OOP sensing system may include a user interface that communicates with a controller. In example embodiments, the interface includes two lights, and the controller is configured to illuminate the first light if fluid flows through the flow channel and the second light if fluid is not flowing in the flow channel. In various embodiments, either light may be used to indicate that fluid is present in the flow channel but is not flowing. In some examples, the system includes a third light, wherein the controller may illuminate the first light (e.g., a green light) if fluid flows through the flow channel, the controller may illuminate the second light (e.g., a red light) if fluid is not present in the flow channel, and the controller may illuminate the third light (e.g., a yellow light) if fluid is present in the flow channel but is not flowing. Other indicators, such as constantly lit lights, flashing lights, and off lights, may be used.

[0171] Additionally or alternatively, in some embodiments, the user interface includes a graphical display screen configured to output text messages indicating the flow status to the user and / or one or more speakers configured to output sound indicating the flow status to the user.

[0172] In some examples, the thermistor, along with, for example, ADC 7 and / or controller 5, is configured to cause the fluid flowing through the flow channel of the OOP sensor to... Figure 10 The signal becomes more negative. However, in other configurations, the fluid flowing through the flow channel can make the signal more positive, for example, by measuring the opposite polarity at the ADC. In some examples, a positive temperature coefficient thermistor can be used, which changes the behavior of the thermistor as the fluid experiences different temperatures due to the flow in the flow channel.

[0173] Therefore, in some examples, a signal above a first predetermined threshold may correspond to fluid flowing in the flow channel, and a signal below a second predetermined threshold may correspond to the absence of fluid in the flow channel.

[0174] In some examples, the controller (e.g., Figure 2The controller 5) is configured to determine the operating state of the pump (e.g., pump 102 in Figure 1). The controller may be configured to use pump status information to determine the fluid flow state through the OOP sensor. In some examples, the OOP sensor provides an output indicating the fluid flow state only when the pump is operating. In some examples, if the controller determines that the pump is on and no fluid is flowing in the OOP sensor, the controller may be configured to provide an output indicating a product depletion event, for example, via a user interface. For example, a product depletion event indicated by the absence of fluid (e.g., no liquid product from the product reservoir) may indicate that the fluid source (e.g., the reservoir) has been depleted.

[0175] In some implementations, the controller may be programmed with one or more additional thresholds, such as a threshold amount of time before the pump is operational before indicating a product depletion event. For example, in some implementations, for a liquid product that releases gas and is to be pumped from a reservoir through an OOP sensor, initial pumping may cause the gas released from the liquid to be pumped through the corresponding line before the liquid flows through the corresponding line. Therefore, the OOP sensor may not sense the presence of liquid until a certain amount of time after the pump is started. In some implementations, a predetermined amount of time is required between pump start-up and indication of a product depletion event to reduce false detections of the product depletion event. This predetermined amount of time may be calibrated based on, for example, system configuration, liquid product properties, and / or other system properties.

[0176] Additional predetermined thresholds can be calibrated for a given system, including, for example, a first predetermined threshold and a second predetermined threshold corresponding to the detection of the presence or absence of fluid. Additionally or alternatively, in some embodiments, measurement signals from the OOP sensor can be analyzed to provide additional information about the system. For example, the measurement signals can provide information indicating pump malfunction, pipe breakage, the presence of air bubbles in the pipeline, or other flow system characteristics. In some embodiments, the controller can be configured to analyze the measurement signals to detect one or more of these occurrences.

[0177] Figure 20 An example graph of a measurement signal over time that can be used to detect bubbles in an OOP sensor is shown. As illustrated in the example, in some embodiments, when the measurement signal is below a first predetermined threshold of 2000, the controller can determine that fluid is flowing in the flow channel, such as in… Figure 20During time periods t1 and t3, when the measured signal is above a second predetermined threshold 2010, the controller can determine that there is no fluid in the flow channel, such as during time period t5. When the measured signal is between a first predetermined threshold 2000 and a second predetermined threshold 2010, the measured signal can be analyzed to determine further information about the flow state. For example, the measured signal pattern in time period t2 may indicate that fluid is present in the flow channel but is not flowing, while the measured signal pattern in time period t4 may indicate that fluid with bubbles is flowing through the flow channel. The controller can be configured to recognize patterns in the measured signals and output information about the flow state, such as the presence of bubbles in the flow channel.

[0178] In some implementations, when the OOP sensor is arranged in certain orientations, it provides the maximum temperature difference between a first sensing region and a second sensing region, and a greater distinction between average measurements associated with flowing fluid and those without fluid. For example, in some cases, this temperature difference is maximized when the fluid flows vertically upward through the flow channel. Therefore, in some cases, during operation, the OOP sensor is arranged such that the fluid flows vertically through the flow channel and upward through the flow channel. In some examples, a deviation of approximately 15 degrees from the vertical flow direction results in substantially similar performance to that of the vertical orientation.

[0179] In some examples, various orientations are possible. For instance, in some examples, when horizontally oriented or facing another direction, the temperature difference between the first sensing area and the second sensing area creates a detectable distinction between flow states (e.g., fluid flowing through a flow channel and fluid not present in the flow channel). Generally, various embodiments can be used in various orientations.

[0180] Various exemplary implementations have been described. These and other examples are within the scope of this disclosure.

Claims

1. A product exhaustion (OOP) sensing system, comprising: A housing, the housing including a first surface and defining a flow channel; An inlet that fluidly connects the flow passage of the housing to the outside of the housing; An outlet that fluidly connects the flow channel of the housing to the outside of the housing; A circuit board coupled to the first surface of the housing; A thermistor bridge, supported by a circuit board and comprising a plurality of thermistors, includes a first branch and a second branch. The first branch has a first thermistor connected in series with a second thermistor and a first point located between the first and second thermistors. The second branch has a third thermistor connected in series with a fourth thermistor and a second point located between the third and fourth thermistors. The first and second branches are arranged in parallel between the power supply side and the reference side of the thermistor bridge, such that the first and third thermistors are coupled to the power supply side of the thermistor bridge, and the second and fourth thermistors are coupled to the reference side of the thermistor bridge. power supply; A switch, the switch being coupled to the power source; as well as A controller, which communicates with the switch and is configured to control the operation of the switch to selectively allow current to flow through the switch from the power supply to the thermistor bridge; and in The first thermistor and the fourth thermistor are located in the first sensing region and form a first pair of thermistors; The second thermistor and the third thermistor are located in a second sensing region different from the first sensing region and form a second pair of thermistors; The housing is configured such that: (i) The thermal resistance between the flow channel and the first sensing region is lower than the thermal resistance between the flow channel and the second sensing region, and / or (ii) The fluid flowing in the flow channel is directed more towards the first sensing area than the second sensing area; and The controller is configured to: The switch is placed in the ON state to allow current to flow from the power source to the thermistor bridge for a heating duration. At the end of the heating duration, the switch is turned off to prevent current from flowing to the thermistor bridge. The switch is held in the off state for a delay duration. After the delay duration ends and during the reading duration, a plurality of measurement pulses are provided, each of the measurement pulses having a measurement pulse duration, and the plurality of measurement pulses being provided at a measurement frequency; During each of the plurality of measurement pulses, a measurement signal value representing the voltage between the first point on the first branch of the thermistor bridge and the second point on the second branch of the thermistor bridge is received. The average measurement signal value is determined based on the measurement signal value received during the reading duration; and The flow state through the flow channel is determined based on the average measured signal value.

2. The OOP sensing system according to claim 1, wherein: The flow channel includes a cylindrical channel; The first surface of the housing includes a first region and a second region, wherein the housing is thinner in the first region than in the second region; The circuit board is coupled to the first surface of the housing, such that: The first sensing area is positioned above the first area of ​​the first surface, such that the first area of ​​the first surface separates the first pair of thermistors from the flow channel. and The second sensing area is positioned above the second area of ​​the first surface, such that the second area of ​​the first surface separates the second pair of thermistors from the flow channel.

3. The OOP sensing system according to claim 1, wherein: The flow channel includes a cylindrical channel; and The circuit board is curved, such that the first sensing area is closer to the flow channel than the second sensing area.

4. The OOP sensing system according to claim 1, wherein: The first surface includes an aperture extending through the first surface; and The circuit board is coupled to the first surface of the housing, such that: The first sensing area is positioned above the orifice extending through the first surface, such that the first surface does not separate the first pair of thermistors from the flow channel; and The second sensing area is positioned on the circuit board at a location not above the aperture extending through the first surface, such that the first surface separates the second pair of thermistors from the flow channel.

5. The OOP sensing system of claim 4, further comprising a protective layer positioned between the first pair of thermistors and the flow channel, such that the protective layer is exposed to the flow channel through the orifice extending through the first surface.

6. The OOP sensing system of claim 5, wherein the protective layer comprises acrylic or Teflon.

7. The OOP sensing system according to claim 5, wherein the protective layer includes the circuit board.

8. The OOP sensing system of claim 7, wherein the circuit board has a thickness between about 0.025 mm and 0.2 mm.

9. The OOP sensing system according to claim 7 or 8, wherein the circuit board comprises a glass epoxy laminate FR-4 or polyimide.

10. The OOP sensing system of any one of claims 4 to 9, further comprising an insert configured to be inserted into the aperture in the first surface and including an aperture extending through the insert, wherein the circuit board, the first surface of the housing, and the insert are arranged such that the first pair of thermistors are positioned above the aperture extending through the first surface of the housing and above the aperture extending through the insert, such that neither the first surface of the housing nor the insert separates the first pair of thermistors from the flow channel.

11. The OOP sensing system of claim 10, wherein the flow channel defined by the housing includes a first half of a tubular flow channel, and wherein the insert includes an inner surface defining a second half of the tubular flow channel, and is configured such that when the insert is inserted into the orifice in the first surface, the flow channel defined by the housing and the inner surface of the insert engage to form a closed tubular flow channel.

12. The OOP sensing system of claim 11, wherein the closed tubular flow channel includes a bend in the tubular flow channel toward the first surface of the housing.

13. The OOP sensing system according to any one of claims 1 to 12, further comprising a flow obstruction positioned in the flow channel, the flow obstruction being configured to guide fluid flowing through the flow channel toward the first surface of the housing.

14. The OOP sensing system according to any one of claims 1 to 12, wherein the flow channel includes a bend in the flow channel toward the first surface of the housing.

15. The OOP sensing system according to any one of claims 1 to 14, wherein determining the flow state within the flow channel comprises: If the average measured signal value satisfies a first predetermined threshold condition, it is determined that fluid is flowing in the flow channel; and If the average measurement signal value meets a second predetermined threshold condition, it is determined that the fluid does not exist in the flow channel.

16. The OOP sensing system according to claim 15, wherein: The average measurement signal value that satisfies the first predetermined threshold condition includes an average measurement signal value that is lower than the first predetermined threshold; and The average measurement signal value that satisfies the second predetermined threshold condition includes an average measurement signal value that is higher than a second predetermined threshold, wherein the second predetermined threshold is higher than the first predetermined threshold.

17. The OOP sensing system of claim 16, wherein determining the flow state within the flow channel further comprises determining that fluid exists in the flow channel but is not flowing if the average measurement signal value is between the first predetermined threshold and the second predetermined threshold.

18. The OOP sensing system according to any one of claims 1 to 17, wherein each of the plurality of thermistors comprises a negative temperature coefficient (NTC) thermistor.

19. The OOP sensing system according to any one of claims 1 to 18, further comprising an analog-to-digital converter (ADC) communicating with the first point of the thermistor bridge and the second point of the thermistor bridge, wherein the controller is configured to receive the measurement signal value from the ADC.

20. The OOP sensing system according to any one of claims 1 to 19, further comprising a current-limiting resistor connected between the switch and the power supply side of the thermistor bridge, such that when the switch is closed, current flows from the power supply through the switch and through the current-limiting resistor to the power supply side of the thermistor bridge.

21. The OOP sensing system according to any one of claims 1 to 20, wherein the power supply comprises a 5-volt power supply.

22. The OOP sensing system according to any one of claims 1 to 21, wherein the housing is oriented such that fluid flows vertically upward through the flow channel.

23. The OOP sensing system according to any one of claims 1 to 22, wherein the controller is configured to: Receive a second signal representing the voltage drop across one of the plurality of thermistors; and For each received measurement signal value, a corrected measurement signal value is calculated based on the received second signal; and where Determining the average measurement signal value based on the measurement signal values ​​received during the reading duration includes averaging the corrected measurement signal values ​​during the reading duration.

24. The OOP sensing system of claim 23, wherein the second signal represents the voltage drop across the second thermistor.

25. The OOP sensing system of claim 23, wherein calculating the corrected measurement signal value comprises multiplying the measurement signal value by a correction coefficient, wherein the correction coefficient comprises a fourth-order polynomial of the second signal.

26. The OOP sensing system according to any one of claims 1 to 22, further comprising a separate thermistor supported by the circuit board and separate from the first thermistor, the second thermistor, the third thermistor, and the fourth thermistor, wherein the controller is configured to: Receive a second signal representing the voltage drop across the independent thermistor; and For each received measurement signal value, a corrected measurement signal value is calculated based on the received second signal; and where Determining the average measurement signal value based on the measurement signal values ​​received during the reading duration includes averaging the corrected measurement signal values ​​during the reading duration.

27. The OOP sensing system of claim 26, wherein the controller is further configured to calculate the temperature based on the second signal.

28. The OOP sensor of claim 27, wherein the controller is configured to calculate the correction measurement signal value based on the calculated temperature.

29. The OOP sensor of claim 28, wherein the controller is configured to use the time derivative of the calculated temperature to calculate the corrected measurement signal value.

30. The OOP sensor of claim 28, wherein the controller is configured to determine the measurement frequency based on the calculated temperature.

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