Bipolar mutual capacitance liquid sensing

Abstract

The invention is entitled "Bipolar Mutual Capacitance Liquid Sensing." The invention provides a liquid level sensing controller that includes a signal generator circuit for generating an excitation signal. The controller also includes a connection for routing an inverted version of the excitation signal to a first pole electrode of a first capacitor. The first pole electrode is coupled to a container for holding a liquid. The controller also includes a connection for routing the excitation signal to a second pole electrode of a second capacitor. The second pole electrode is coupled to the container. The controller also includes a connection to a sense electrode for forming the first capacitor with the first pole electrode and the second capacitor with the second pole electrode. The controller also includes a measurement circuit configured to measure a charge at the sense electrode and determine whether the liquid in the container has reached a liquid level of the second pole electrode based on the measured charge.

Description

Technical Field

[0001] This disclosure relates to liquid level sensing, and more specifically, to bipolar mutual capacitance liquid sensing. Background Technology

[0002] Various techniques exist for sensing the liquid level in a container. These include contact or mechanical sensors, optical sensors for observing liquid levels, inductive sensors that measure the electromagnetic induction generated by the liquid, Hall effect sensors that measure the magnetic field generated by the liquid, and capacitive sensors.

[0003] Capacitive sensors used for measuring liquid levels include self-capacitance sensors and unipolar mutual capacitance sensors. However, the inventors of the embodiments of this disclosure have found that these capacitive sensors drift with environmental conditions such as humidity or temperature. Therefore, triggering may be caused by changes in liquid level or environmental conditions. These capacitive sensors require a reference value when water does not cover the sensing area and calibration is needed. Furthermore, these capacitive sensors cannot discern the initial state of the sensor, and therefore it can be assumed that the sensor is not triggered upon startup. The embodiments of this disclosure address these drawbacks of other solutions found by the inventors of these embodiments. Summary of the Invention

[0004] Embodiments of this disclosure include a liquid level sensing controller. The controller may include signal generator circuitry configured to generate an excitation signal. The controller may include a first connector configured to route an inverted excitation signal to a first electrode of a first capacitor, the first electrode being coupled to a container configured to hold liquid. The controller may include a second connector configured to route the excitation signal to a second electrode of a second capacitor, the second positive electrode being coupled to the container. The controller may include a third connector to a sensing electrode. The sensing electrode may be configured to form a first capacitor together with the first electrode and a second capacitor together with the second electrode. The controller may include measurement circuitry configured to measure a charge at the third connector and determine, based on the measured charge, whether the liquid in the container has reached the level of the second electrode. The polarity of the first electrode may be opposite to that of the second electrode.

[0005] Embodiments of this disclosure may include a method for sensing a liquid level. The method may include generating an excitation signal. The method may include routing the excitation signal in reverse phase at a first connection to a first electrode of a first capacitor, the first electrode being coupled to a container configured to hold liquid. The method may include routing the excitation signal at a second connection to a second electrode of a second capacitor, the second positive electrode being coupled to the container. The method may include forming a first capacitor together with the first electrode and the sensing electrode at a third connection with a sensing electrode. The method may include forming a second capacitor together with the second electrode and the sensing electrode, measuring the charge at the third connection, and determining, based on the measured charge, whether the liquid in the container has reached the level indicated by the second electrode. The polarity of the first electrode is opposite to that of the second electrode. Attached Figure Description

[0006] Figure 1 This is an illustration of an exemplary system for bipolar mutual capacitance liquid sensing according to an embodiment of the present disclosure.

[0007] Figure 2 This is a more detailed illustration of an electrode assembly for bipolar mutual capacitance liquid sensing according to an embodiment of the present disclosure.

[0008] Figure 3 This is a more detailed illustration of a controller for bipolar mutual capacitance liquid sensing according to an embodiment of the present disclosure.

[0009] Figure 4 This is an illustration of a method for bipolar mutual capacitance liquid sensing according to an embodiment of the present disclosure. Detailed Implementation

[0010] Embodiments of this disclosure may include a liquid level sensing controller. The liquid level sensing controller may include signal generator circuitry configured to generate an excitation signal. The signal generator circuitry may be implemented by any suitable combination of analog circuitry, digital circuitry, or instructions for execution by a processor. The excitation signal may include the rising or falling edge of a voltage pulse. The signal generator circuitry may include a first connection configured to route the inverted excitation signal to a first electrode of a first capacitor. The first electrode may be coupled to a container configured to hold liquid. The controller may include a second connection configured to route the excitation signal to a second electrode of a second capacitor. A second positive electrode may be coupled to the container. The controller may include a third connection to a sensing electrode. The sensing electrode may be configured to form a first capacitor together with the first electrode and a second capacitor together with the second electrode. The controller may include measurement circuitry configured to measure the charge at the third connection and determine, based on the measured charge, whether the liquid in the container has reached the level of the second electrode. The connection may include any suitable electronic or electrical connection. The measurement circuit can be implemented using analog circuitry, digital circuitry, or any suitable combination of instructions executed by a processor. The polarity of the first electrode can be opposite to that of the second electrode. For example, the first electrode can be positive and the second electrode can be negative. In another example, the first electrode can be negative and the second electrode can be positive. The electrodes can be located inside or outside the container.

[0011] In any of the above embodiments, the charge at the third connector may represent the relative capacitance between the first capacitor and the second capacitor. In any of the above embodiments, the measuring circuit is configured to determine, based on the charge at the third connector and the change in relative capacitance between the first and second capacitors, that the liquid in the container has reached the level of the first electrode. In any of the above embodiments, the controller further includes a fourth connector to the third electrode of the third capacitor, the third electrode being coupled to the container. The second connector may be further configured to route an excitation signal to the second electrode of the second capacitor when checking the proximity of the liquid in the container to the second electrode, and to route a ground signal to the second electrode of the second capacitor when checking the proximity of the liquid in the container to the third electrode. In any of the above embodiments, the fourth connector is configured to route an excitation signal to the third electrode of the third capacitor when checking the proximity of the liquid in the container to the third electrode, and to route a ground signal to the third electrode of the third capacitor when checking the proximity of the liquid in the container to the second electrode. In any of the above embodiments, the sensing electrode is further configured to form a third capacitor together with the third electrode. In any of the above embodiments, the first electrode may be coupled to the container outside the possible range of the liquid. In any of the above embodiments, the excitation signal applied to the second capacitor may be configured to cause detection of the liquid level in the detection container. In any of the above embodiments, the inversion of the excitation signal applied to the first capacitor may be configured to cause compensation for capacitance changes in the second capacitor due to environmental changes.

[0012] Embodiments of this disclosure may include a system. The system may include any of the liquid level sensing controllers described above. The system may include an electrode assembly. The electrode assembly may include the sensing electrode and the polar electrode described above.

[0013] Embodiments of this disclosure may include methods for determining liquid levels. These methods may include the operation of any of the controllers and systems described above.

[0014] Figure 1This is an illustration of an exemplary system 100 for bipolar mutual capacitance liquid sensing according to embodiments of the present disclosure. System 100 can be used to sense the level of a liquid in any suitable application, such as in consumer devices, tanks, motor vehicle applications, reservoirs, water, wastewater, utilities, or oil and gas. System 100 can be configured to determine the level l of a liquid in any suitable container 104. Although container 104 is shown as a cylinder, any container of suitable shape, arrangement, or orientation may be used. The liquid level l can be defined by reference to any suitable other portion of container 104, such as the bottom of container 104. System 100 can be configured to measure l periodically, on demand, or according to any suitable stimulus or criterion. System 100 can be configured to report the measured value of l, or periodically, on demand, or according to any suitable stimulus or criterion to generate an alert that l has reached an upper or lower threshold.

[0015] System 100 may include controller 102. Figure 3 The controller 102 is shown in more detail below and will be discussed in further detail. The controller 102 may be implemented using digital circuitry, analog circuitry, instructions for execution by a processor, or any suitable combination thereof conforming to the teachings of this disclosure. In one embodiment, the controller 102 may include an interface for a plurality of bipolar mutual capacitance sensors or portions thereof. The controller 102 may include signal generation circuitry to be applied to the bipolar mutual capacitance sensors. Furthermore, the controller 102 may include circuitry for integrating signals received from the bipolar mutual capacitance sensors.

[0016] System 100 may include an electrode assembly 104 coupled to container 106. The electrode assembly 106 may be coupled to container 104 externally or internally. Figure 2 Electrode assembly 106 is shown in more detail below and will be discussed in further detail. Electrode assembly 106 may include any suitable number and type of electrodes. Such electrodes may be arranged in 1:1 or 1:N pairs. Furthermore, such electrodes may form a capacitor upon receiving an excitation signal. An excitation signal may be received from controller 102. The excitation signal may be routed to the transmitting and receiving electrodes of electrode assembly 106. When applied to a pair of electrodes, the excitation signal facilitates the measurement of the charge between the electrodes. The measurement of the charge between the electrodes can be used to measure the capacitance between the electrodes. The capacitance measurement can be used as an assessment of the proximity of the liquid in container 104. The position of the electrodes relative to container 104 may be known, and therefore the associated capacitance measurement can be used to determine whether the liquid has reached a given liquid level l in container 104, wherein the position of the electrode performing proximity detection or change may indicate that the liquid has reached the known position of the electrode.

[0017] The controller 102 can be configured to sequentially measure the capacitance at the electrode pairs of the electrode assembly 106 in the container 104 and report the proximity of the liquid in any suitable manner. The controller 102 may, for example, begin with the electrode pairs at the top of the electrode assembly 106 and work towards the electrode pairs at the bottom of the electrode assembly 106. In one embodiment, the controller 102 may evaluate the capacitance between all electrode pairs of the electrode assembly 106. The controller 102 may then report the capacitance of each such electrode pair to, for example, a display or warning device 108. The controller 102 may report whether the proximity of the liquid to each such electrode pair has been detected. The controller 102 may report a given liquid level l associated with the highest electrode pair that detected proximity to the liquid. In another embodiment, while determining the proximity of the liquid in the container 104 while evaluating the electrode pairs from top to bottom, the controller 102 may report this detection and the liquid level l of the electrode pair that performed the detection.

[0018] Figure 2 This is a more detailed illustration of an electrode assembly 106 for bipolar mutual capacitance liquid sensing according to an embodiment of the present disclosure. Furthermore, Figure 2 The charge applied to the various electrodes of the electrode assembly 106 over time is shown in order to scan the capacitance value and thus the liquid proximity of the electrodes.

[0019] Electrode assembly 106 may include sensing electrode 210. During polling of the electrodes in electrode assembly 106, sensing electrode 210 may be used to connect to a collection node or sensing node of controller 102. Sensing electrode 210 may be the first electrode in a pair of electrodes formed for proximity detection. Sensing electrode 210 may include high input impedance. When connected to sensing electrode 210, controller 102 may precharge sensing electrode 210 to half of the supply voltage. During subsequent measurements, the voltage of sensing electrode 210 may fluctuate.

[0020] Electrode assembly 106 may include two or more second electrodes or pole electrodes 212A-212H. Each of pole electrodes 212A-212G can be connected to a positive signal from controller 102 during polling of a given pole electrode, and connected to ground during polling of the other pole electrodes 212A-212G. Pole electrode 212H can be connected to a negative signal from controller 102 during polling of pole electrodes 212A-212G.

[0021] The electrodes 212A-212H can be configured to operate as the transmitting electrodes of a capacitive sensor. The sensing electrode 210 can be configured to operate as the receiving electrode of a capacitive sensor. Therefore, each pair of electrodes, including the sensing electrode 210 and one of the electrodes 212A-212H, can be a capacitive sensor and can be represented as a capacitor.

[0022] exist Figure 2 In this example, electrode assembly 106 may be arranged vertically along the side of container 104. Therefore, electrode electrodes 212A-212G may be arranged vertically from bottom to top within electrode assembly 106. Electrode electrode 212H may be arranged at the top of electrode assembly 106. Each of electrode electrodes 212A-212G may be configured to indicate whether liquid in container 104 has reached a vertical position associated with a given one of electrode electrodes 212A-212G. Based on the detection or proximity sensing provided by a given one of electrode electrodes 212A-212G and the known position or height of electrode electrodes 212A-212G, system 100 is able to determine the liquid level l in container 104.

[0023] When sensing electrode 210 is connected to the collection node of controller 102, electrode 212H is connected to a negative signal, and one of electrodes 212A-212G is connected to a positive signal. A first capacitive sensor may be formed between electrode 212H and sensing electrode 210, and a second capacitive sensor may be formed between sensing electrode 210 and one of electrodes 212A-212G. The capacitive sensors can be configured to detect proximity to liquid in container 104.

[0024] To scan the electrode assembly to obtain proximity to the liquid in container 104, at (1), sensing electrode 210 can be connected to the collection node of controller 102, a negative signal or pulse can be applied to electrode 212H, grounding can be applied to electrode 212B-212G, and a positive signal or pulse can be applied to electrode 212A. If the liquid in container 104 is at the height of electrode 212A, then the capacitive sensor formed by the combination of electrode 212H, electrode 212A, and sensing electrode 210 can indicate to system 100 the proximity of the liquid to electrode 212A.

[0025] At (2), the sensing electrode 210 can be connected to the collection node of the controller 102, a negative signal or pulse can be applied to the electrode 212H, grounding can be applied to the electrodes 212A and 212C-212G, and a positive signal or pulse can be applied to the electrode 212B. If the liquid in the container 104 is at the height of the electrode 212B, then the capacitive sensor formed by the combination of the electrode 212H, the electrode 212B, and the sensing electrode 210 can indicate to the system 100 the proximity of the liquid to the electrode 212B.

[0026] At (3)-(7), the same polling can be performed on the electrodes 212C-212G.

[0027] Although Figure 2The method is described as applying a negative signal to electrode 212H, applying a positive signal to a corresponding one of electrodes 212A-212G, and connecting sensing electrode 210 to the collection node of controller 102. However, any suitable signal and voltage can be applied to generate a capacitive sensor between electrode 212H and sensing electrode 210, and between sensing electrode 210 and a given one of electrodes 212A-212G. In one embodiment, a negative signal can be applied to a given number of electrodes 212A-212G, and a positive signal can be applied to electrode 212H. Any voltage value can be used for the negative and positive signals, provided that a falling edge is applied to electrode 212 while a rising edge is applied to a corresponding one of electrodes 212A-212G, or provided that a rising edge is applied to electrode 212 while a falling edge is applied to a corresponding one of electrodes 212A-212G. The rising and falling edges can have approximately the same absolute value and rate of change.

[0028] Figure 3 This is a more detailed illustration of a controller 102 for bipolar mutual capacitance liquid sensing according to an embodiment of the present disclosure. Furthermore, Figure 3 The portion of the electrode array 106 that has been formed into a capacitive sensor is shown.

[0029] The controller 102 may include a terminal 306 for connection to the electrode 212H of the electrode assembly 106. Additionally, the controller 102 may include a terminal 320 for connection to the sensing electrode 210 of the electrode assembly 106. Furthermore, the controller 102 may include terminals 308A-308G for connection to each of the electrode electrodes 212A-212G.

[0030] The connection between the controller 102, the sensing electrode 210, and the electrode electrodes 212A-212H can form a capacitive sensor in the electrode assembly 106. Figure 3 The capacitors 310, 312A-312G are represented in the middle. The connection from terminal 306 to electrode 212H and from terminal 320 to sensing electrode 210 can form capacitor 310.

[0031] The connection from terminal 308A to electrode 212A and from terminal 320 to sensing electrode 210 forms capacitor 312A. The connection from terminal 308B to electrode 212B and from terminal 320 to sensing electrode 210 forms capacitor 312B. Similarly, the connection from terminals 308C-308G to electrodes 212C-212G and from terminal 320 to sensing electrode 210 forms capacitors 312C-312G (terminals 308C-308F, capacitors 312C-312F, and associated connections and branches are not shown).

[0032] Controller 102 may include a sensing signal generator 302. The sensing signal generator 302 may be configured to generate pulse signals, excitation signals, transmission signals, or any other suitable signals for the transmitting electrodes of a capacitive sensor. The sensing signal generator 302 may be implemented using analog circuitry, digital circuitry, instructions for execution by a processor, or any suitable combination thereof. Figure 3 In the example, the sensing signal generator 302 can be configured to generate a positive pulse signal when the controller 102 evaluates the capacitance of a given capacitive sensor.

[0033] A positive pulse signal generated by the sensing signal generator 302 can be routed to the inverter 304, and the resulting negative pulse signal can be routed to terminal 306 to be applied to electrode 212H. The positive pulse signal generated by the sensing signal generator 302 can be further routed to switch 318, which can then route the positive pulse signal to one of terminals 308A-308G to be applied to one of electrodes 212A-212G.

[0034] Switch 318 can be implemented in any suitable manner, such as a multiplexer, switch structure, switch matrix, or other suitable structure. Switch 318 can be configured to send a positive pulse signal to one of the terminals 308A-308G and send a ground signal to the other terminals of terminals 308A-308G.

[0035] Controller 102 may include control circuitry 320. Control circuitry 320 may be implemented in any suitable manner, such as analog circuitry, digital circuitry, instructions for execution by a processor and a processor, or any suitable combination thereof. For example, control circuitry 320 may be implemented using digital logic, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), processors, or microcontrollers. Control circuitry 320 may be configured to control the operation, timing, polling, and result collection of sensors of system 100. For example, control circuitry 320 may be configured to specify when sensing signal generator 302 generates pulses to perform measurements in electrode assembly 106. Furthermore, control circuitry 320 may be configured to specify which terminals of switch 318 will receive pulses and which terminals will receive ground signals. Thus, control circuitry 320 may specify which of electrodes 212A-212G will perform proximity detection of liquid in container 104 at a given time. Additionally, control circuitry 320 may be configured to collect measurement results, store results in memory, or report these results to other entities 108.

[0036] The capacitance of capacitors 310 and 312A-312H can vary depending on whether a given one of these capacitors is very close to the liquid in container 104. In one embodiment, electrode 212H can be excluded from the range of the liquid in container 104. Therefore, the capacitance of capacitor 310 is not affected by the liquid level l in container 104. Thus, the capacitance of capacitor 310 can remain constant across all liquid levels in container 104. However, the capacitance of capacitor 310 can vary depending on the different environmental conditions in which system 100 is used, such as temperature, humidity, or electromagnetic interference. If a given one of electrodes 212A-212G is close to the liquid in container 104, the capacitance between the given electrode and sensing electrode 210 will change, and therefore the capacitance of the associated capacitors in capacitors 312A-312G will change. However, the capacitance of capacitors 312A-312G can also vary depending on the different environmental conditions in which system 100 is used, such as temperature, humidity, or electromagnetic interference.

[0037] Controller 102 can be configured to determine whether the capacitance of one or more of capacitors 312A-312G has changed, thereby indicating the proximity of the corresponding electrode of electrode 212A-212G to the liquid in container 104. Controller 102 can then poll or evaluate each or one or more of capacitors 312A-312G. Controller 102 can be configured to evaluate the capacitance of a given one of capacitors 312A-312G and compare the capacitance of the given one of capacitors 312A-312G with the capacitance of capacitor 310. Controller 102 can be configured to compare the capacitance of one of capacitors 312A-312G with the capacitance of capacitor 310 by, for example, evaluating the charge at a point between a given one of capacitors 312A-312G and capacitor 310.

[0038] When selecting a given capacitor among capacitors 312A-312G for evaluation by applying a positive signal to one of the corresponding terminals 308A-308G, grounding can be applied to the other terminals among terminals 308A-308G, and a negative signal can be applied to terminal 306. Taking capacitor 312A as an example, the top plate (electrode 212H) of capacitor 310 has a negative voltage, the bottom plate (electrode 210) of capacitor 310 is at the same voltage as the top plate (electrode 210) of capacitor 312A, and the bottom plate (electrode 212A) of capacitor 312A has a positive voltage. Based on the capacitance of capacitors 312A and 310, different amounts of charge will accumulate on the bottom plate of capacitor 310 and the top plate of capacitor 312A. If the capacitances of capacitors 312A and 310 are the same, a certain amount of charge will accumulate. It is possible that the electrode 212A of capacitor 312A is not adjacent to the liquid in container 104.

[0039] The parasitic capacitance of capacitor 312A may drift due to changes in humidity, temperature, electromagnetic interference, or other environmental conditions. This change in capacitance is slow, but it cannot be distinguished from capacitance changes caused by liquid in container 104 based on the rate of change, as such changes can also be slow. In one embodiment, including capacitor 310 can explain this slow environmental change in the capacitance of capacitor 312A, because both capacitors, implemented in the common electrode assembly 106, on the same printed circuit board, or by replicating materials, may have the same expected capacitance. Capacitor 310 and capacitor 312A may experience the same environmental changes. Due to the applied signal from the sensing signal generator 302, capacitor 310 may have the same expected charge as capacitor 312A, although with opposite polarity. Therefore, capacitor 310 can provide compensation for the capacitance changes experienced by capacitor 312A due to environmental variations.

[0040] Therefore, if capacitors 312A and 310 have the same capacitance, a first amount of charge will accumulate between these capacitors, and this amount of charge may indicate that electrode 212A is not adjacent to the liquid in container 104. In one embodiment, if capacitors 312A and 310 have different capacitances, a second amount of charge will accumulate. This may occur when electrode 212A of capacitor 312A is adjacent to the liquid in container 104. In this case, controller 102 may detect the second amount of charge and interpret it as an indication that the liquid in container 104 has reached electrode 212A. Controller 102 may determine the second amount of charge and interpret it relative to a threshold as an indication that the liquid in container 104 has approached electrode 212A. In another embodiment, when the capacitances of these capacitors are the same, zero charge may accumulate between capacitors 310 and 312A, and when the capacitances of these capacitors are different, non-zero charge may accumulate between capacitors 310 and 312A, i.e., the first amount of charge may be zero.

[0041] Controller 102 may include any suitable circuitry for evaluating the charge accumulating between capacitors 310 and 312A. For example, controller 102 may include measurement circuitry, such as integrator 314. Integrator 314 may be implemented, for example, digital circuitry, analog circuitry, or any suitable combination thereof. Integrator 314 may be configured to determine the charge accumulating between capacitors 310 and 312A. Integrator 314 may output an analog signal indicating the accumulated charge. The analog signal may be routed to analog-to-digital converter (ADC) 316. The charge value from ADC 316 may be provided to control circuitry 320 or output to other entities such as a display or warning device 108.

[0042] The exemplary operation of the controller 102 described above with respect to capacitor 312A can also be used for any of capacitors 312B-312G.

[0043] Figure 4 This is an illustration of a method 400 for bipolar mutual capacitance liquid sensing according to an embodiment of this disclosure. It can be derived from, for example... Figures 1 to 3 The steps of method 400 may be executed by any suitable part of the components (such as by controller 102). Method 400 may be initiated at any suitable point (such as at step 405). The steps of method 400 may optionally be repeated, omitted, or recursively executed. The steps of method 400 may be executed in the order discussed below, or in any other suitable alternative order. Furthermore, with Figure 4Compared to the steps shown, more or fewer steps may be performed during the execution of method 400. Some portions of method 400 may be executed by instructions for a processor stored in a non-transitory machine-readable medium. When loaded and executed by the processor, the instructions may cause the processor to execute the steps of method 400.

[0044] At step 405, it can be determined whether the liquid level in the container has been found. This determination may be made, for example, by a larger appliance or system on demand, periodically, or according to any other suitable criterion. If the liquid level is to be found, method 400 may proceed to step 410. Otherwise, method 400 may proceed to step 470.

[0045] At step 410, a positive sensing pulse may be generated. At step 415, the positive sensing pulse may be inverted to generate a negative sensing pulse. At step 420, a negative sensing pulse may be sent to a negative electrode in an electrode assembly adjacent to or within the container. Sending a negative sensing pulse to the negative electrode may charge a negative capacitor formed by the negative electrode and the sensing electrode. The sensing electrode may be connected to a cluster node of a controller or other means of performing method 400.

[0046] At step 425, a positive electrode in an electrode assembly adjacent to or disposed within the container can be selected. In one embodiment, a positive electrode that is not yet evaluated as the highest-ranking electrode can be selected.

[0047] At step 430, a positive sensing pulse may be sent to the selected positive electrode. Sending a positive sensing pulse to the selected positive electrode can charge the positive capacitor formed by the selected positive electrode and the sensing electrode.

[0048] At step 435, other positive electrodes in the electrode assembly adjacent to the container that are not currently selected for evaluation may be grounded or otherwise isolated or prevented from affecting the measurements associated with the positive electrode selected for evaluation.

[0049] At step 440, the charge between the negative and positive capacitors can be collected or integrated. At step 445, the collected charge can be converted into a digital value. At step 450, the value of the collected charge can be evaluated to determine the capacitance value of the positive capacitor compared to the capacitance value of the negative capacitor. The relative capacitance value indicated by the collected charge value can indicate whether the liquid has reached the selected positive electrode of the positive capacitor. If the value indicates the proximity of the liquid to the selected positive electrode, method 400 can proceed to step 455. Otherwise, method 400 can proceed to step 460.

[0050] At step 455, a report or other indicator may be generated for the selected positive electrode or its location, indicating that the liquid level in the container has reached the selected positive electrode or its location. Method 400 may then proceed to step 470.

[0051] At step 460, it can be determined whether there is an additional positive electrode that has not yet been evaluated. If so, method 400 can proceed to step 425, where the next electrode can be selected for evaluation. Otherwise, method 400 can proceed to step 465.

[0052] At step 465, it can be determined that the container is empty. Method 400 can then proceed to step 470.

[0053] At step 470, it can be determined whether method 400 is repeatable. Method 400 may be repeated continuously, on demand, or according to other suitable criteria established or controlled by the system in which liquid level detection is performed. If method 400 will be repeated, method 400 may proceed to step 405, or if method 400 will not be repeated, the method may proceed to step 475 to terminate.

[0054] This disclosure has been described according to one or more embodiments, and it should be understood that many equivalents, alternatives, variations, and modifications are possible and within the scope of this disclosure, in addition to those expressly stated. While this disclosure is susceptible to various modifications and alternatives, specific exemplary embodiments thereof have been shown in the accompanying drawings and described in detail herein. However, it should be understood that the description of specific exemplary embodiments herein is not intended to limit this disclosure to the specific forms disclosed herein.

Claims

1. A liquid level sensing controller, comprising: A signal generator circuit configured to generate an excitation signal; A first connector is configured to route the inverted excitation signal to a first electrode of a first capacitor, the first electrode being coupled to a container configured to hold liquid. A switching device configured to distribute the excitation signal to one of a plurality of second electrodes; A plurality of second connectors, each of which is configured to route the excitation signal to a second corresponding electrode of the plurality of second electrodes, the plurality of second electrodes being associated with and coupled to the plurality of second capacitors; A third connector to the sensing electrode, the sensing electrode being configured to form the first capacitor together with the first electrode and to form the plurality of second capacitors together with the plurality of second electrodes; as well as A measuring circuit configured to measure the charge at the third connector and determine, based on the measured charge, whether the liquid in the container has reached the level of one of the plurality of second electrodes; The polarity of the first electrode is opposite to that of one of the plurality of second electrodes. The charge at the third connector represents the relative capacitance between the first capacitor and the second capacitor, and the measuring circuit is configured to determine, based on the change in the relative capacitance, that the liquid in the container has reached the level of one of the plurality of second electrodes.

2. The level sensing controller of claim 1, wherein the switching device includes a multiplexer that feeds the excitation signal to one of the plurality of second electrodes and is configured to ground the remaining second electrodes.

3. The liquid level sensing controller of claim 1, wherein the switching device includes a switching matrix that feeds the excitation signal to one of the plurality of second electrodes and is configured to ground the remaining second electrodes.

4. The liquid level sensing controller of claim 1, wherein the first electrode is coupled to the container outside the possible range of the liquid.

5. The level sensing controller of claim 1, wherein the measurement circuit includes an integrator coupled to the third connector and an analog-to-digital converter coupled to the output of the integrator.

6. A system comprising: An electrode assembly including the sensing electrode, a first electrode of the first capacitor, and the plurality of second electrodes of the second capacitor, the electrode assembly being coupled to the container configured to hold liquid; as well as The liquid level sensing controller according to any one of claims 1-5.

7. The system of claim 6, wherein the sensing electrode comprises a comb having a plurality of electrode fingers, wherein the plurality of second electrodes are arranged vertically to form the second capacitor with the electrode fingers.

8. A method for sensing a liquid level, comprising operations performed by a liquid level sensing controller according to any one of claims 1-5, the operations comprising the following steps: a) Select the first of the plurality of electrodes; b) Feed the excitation signal to the first of the plurality of second electrodes and feed the inverted excitation signal to the first electrode, and ground the remaining second electrodes; c) Processing the received signals from the third connector. d) Repeat steps a) to c) for the other second electrode; e) Determine the liquid level from multiple processed received signals.

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