Detection of high-purity water using pulse signal

Abstract

A water level detection system can include a probe assembly and a sensing circuit coupled to the probe assembly. The sensing circuit can operate in a first mode (e.g., a high-sensitivity DC mode) for detecting high-resistance water by applying a DC pulse signal to one or more probes of the probe assembly, and operate in a second mode (e.g., a lower-sensitivity AC mode) for detecting lower-resistance water by applying an AC signal to the one or more probes of the probe assembly. The sensing circuit can switch between the first and second modes based on detected water resistivity characteristics.

Description

DETECTION OF HIGH-PURITY WATER USING PULSE SIGNALCLAIM OF PRIORITY

[0001] This application is related to and claims priority to United States Provisional Application No. 63 / 754,114, filed on February 5, 2025, and entitled “DETECTION OF HIGH-PURITY WATER USING PULSE SIGNAL,” the entirety of which is incorporated herein by reference.BACKGROUND

[0002] A building (e.g., residence, multi-family dwelling, office building, municipal building or the like) will often include heating, ventilating, and air conditioning (“HVAC”) appliances to control the atmosphere (e.g., temperature) within the building. In some examples, a humidifier is included with an HVAC appliance to control the amount of humidity present in the atmosphere within the building. An example humidifier includes a tank, a heat source, and a valve for introducing water into the tank. As the heat source heats — and ultimately boils — the water inside of the tank, steam escapes the tank through a steam discharge.

[0003] Water can be added to the tank as steam escapes the tank. Water is added to replace the water that was converted to steam and to ensure continued operation of the humidifier. In some examples, a float valve is used to control the introduction of water into the tank. In another example, a water level sensor is installed within the tank and is configured to sense when the water level rises above the sensor. A controller is in communication with a valve to introduce water into the tank when the water level within the tank reaches a predetermined level (e.g., when the water level is below the water level sensor).SUMMARY

[0004] A problem to be solved includes unreliable water level detection in boiling systems that operate across varying water conductivity conditions. Some sensing systems struggle to maintain accurate measurements asmineral concentrations change during boiling operations, causing conductivity variations that can span multiple orders of magnitude, such as from highly purified water (e.g., having resistivity of up to about 18 M -cm) to mineral-rich water (e.g., having resistivity below about 200 O-cm).

[0005] A particular challenge arises from foam formation during boiling of mineral-rich water. The foam can have a three-dimensional matrix structure that is conductive but exhibits much higher electrical resistance compared to the bulk water it forms from, leading to false level readings that can trigger improper water additions and disrupt the boiling process.

[0006] In some examples, existing systems are limited by their inability to adapt to changing water conditions. Some sensor systems that use AC excitation of water level probes become unreliable at high water resistance levels due to parasitic capacitance effects, while DC-only systems can be constrained by electrolysis effects.

[0007] A solution to these and other problems can include or use a dualmode sensing circuit that automatically adapts its sensitivity based on water conductivity characteristics. The system can accurately discriminate between foam and bulk water through dynamic adjustments of reference or threshold values, enabling more accurate level detection and ultimately better-controlled water addition even during vigorous boiling. The solutions discussed herein can maintain reliable level detection across a range of operating conditions, from initial filling with high-resistance water to concentrated low-resistance conditions during extended boiling.

[0008] In an example, the systems discussed herein can be configured to monitor mineral concentration using a calculated concentration factor, enabling proactive water cycling before mineral levels become problematic for continued operation. This approach helps maintain stable boiling rates by preventing both over-filling and excessive mineral concentration.

[0009] In an example, the solutions discussed herein can include or use a water level detection system comprising a probe assembly and a sensing circuit coupled to the probe assembly. The sensing circuit can be configured to operate in a first mode (e.g., a high-sensitivity DC mode) for detecting high-resistance water by applying a DC pulse signal to one or more probesof the probe assembly, and operate in a second mode (e.g., a lower-sensitivity AC mode) for detecting lower-resistance water by applying an AC signal to the one or more probes of the probe assembly. The sensing circuit can be configured to dynamically switch between the first and second modes based on detected water resistivity characteristics.

[0010] In an example, the solutions discussed herein can include or use a probe assembly that includes multiple discrete probes, and each of the probes extends from a common reference plane into a fluid container by different respective amounts. A method of measuring fluid characteristics of a fluid in a container using the probe assembly can include: generating, using a signal generator circuit, a first excitation signal, providing the first excitation signal to the first fluid level probe, after a first settling time and while the first fluid level probe receives the first excitation signal, measuring a first voltage from the first fluid level probe, removing the first excitation signal from the first fluid level probe, generating, using the signal generator circuit, a second excitation signal, in response to removing the first excitation signal from the first fluid level probe and after a blanking time, providing the second excitation signal to the second fluid level probe, after a second settling time and while the second fluid level probe receives the second excitation signal, measuring a second voltage from the second fluid level probe, and providing a fluid level indication of the fluid in the container based on the measured first and second voltages. In other words, the probes can be sampled in a round-robin manner to more accurately detect fluid levels in the fluid container.

[0011] This Summary is intended to provide an overview of the present subject matter. It is not intended to provide an exclusive or exhaustive explanation of an invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but notby way of limitation, various embodiments discussed in the present document.

[0013] FIG. 1 is a cross sectional view of one example of a system for producing vapor.

[0014] FIG. 2 is a side view of one example of a sensor assembly.

[0015] FIG. 3 is a side view of a sensor assembly and a turbulated base fluid.

[0016] FIG. 4 illustrates generally a block diagram of a water level detection system.

[0017] FIG. 5 illustrates generally an example of a sensing circuit for a water level detection system.

[0018] FIG. 6 illustrates generally a first portion of a first method for operating a water level detection system.

[0019] FIG. 7 illustrates generally a second portion of the first method for operating a water level detection system.

[0020] FIG. 8 illustrates generally an example of a method for changing modes of operation of a water level detection system.

[0021] FIG. 9 illustrates generally an example of a method that includes using a probe assembly to provide a fluid level indication of a fluid in a container.DETAILED DESCRIPTION

[0022] FIG. 1 is a cross sectional view of one example of a system 100 for producing vapor. In some examples, the system 100 includes a humidifier, a boiler, or the like. The system 100 shown in FIG. 1 includes a tank 110, or container for bulk fluid or liquid, and the tank 110 defines a reservoir 115. The reservoir 115 is configured to contain a base fluid. In one example, the base fluid includes water (e.g., tap water, deionized water, distilled water, or the like). In some instances, the base fluid is turbulated inside the reservoir 115. In an example, the turbulated base fluid is a fluid having a turbulent, agitated or undulating surface. As described herein, the base fluid is optionally driven by mechanical, fluid or thermodynamic mechanisms intothe turbulated configuration. Optionally, the base fluid is turbulated with one or more fluid or thermodynamic processes that precipitate boiling including, but not limited to, heating of the fluid such as water, decreasing ambient pressure in the reservoir to trigger boiling, or the like.

[0023] Referring again to FIG. 1, in one example, the system 100 includes one or more heaters 130 (e.g., resistive heating elements, boiler tubes or the like). The one or more heaters 130 are configured to supply thermal energy to the base fluid contained within the reservoir 115. In some examples, the system 100 includes a heat exchanger configured to supply thermal energy to the base fluid contained within the reservoir 115. For instance, in one example, the heat exchanger is positioned in the reservoir 115 and is in communication with the base fluid contained within the reservoir 115.Additionally, the heat exchanger is in communication with a heat source (e.g., a boiler, natural gas burner, geo-thermal source, or the like) that supplies thermal energy to a fluid that flows through the heat exchanger, thereby heating the base fluid contained within the reservoir 115. The one or more heaters 130, heat exchanger or the like arc optionally configured to turbulate the base fluid through initiation and maintenance of boiling.

[0024] In some examples, the system 100 includes a cover 140 coupled with the tank 110. The system 100 includes a discharge 145 in communication with the reservoir 115. In some examples, the cover 140 includes the discharge 145 in communication with the reservoir 115. The discharge 145 is an outlet for the base fluid from the reservoir 115. In an example, the turbulated base fluid is boiling water. The boiling water in the reservoir 115 produces steam and the steam flows from the reservoir 115 through the discharge 145. Optionally, the reservoir 115 is sealed (with the exception of the discharge 145) to prevent the base fluid from otherwise escaping from the reservoir 115. Further, sealing the reservoir 115 facilitates the maintenance of specified pressures, temperatures and the like.

[0025] The system 100 includes one or more sensors. In an example, the one or more sensors are included in a probe assembly 120. As shown in the example provided in FIG. 1 the probe assembly 120 includes a first probe 121 and a second probe 122. In some examples, the probe assembly 120includes one or more sensors or probes (e.g., one, two, or three or more sensors or probes). As discussed herein, the one or more probes are configured to monitor a base fluid level (e.g., an actual amount, the volume of, the quantity of, or the like) in the reservoir 115.

[0026] In an example, the system 100 includes an input control valve 150, such as a modulating control valve. The modulating input control valve 150 introduces (e.g., permits flow, inputs, directs, deposits, provides, or the like) an input fluid, such as water, into the reservoir 115. The modulating input control valve 150 is in communication with an input fluid source (e.g., a municipal water system, deionized water source, or the like). In some examples, the modulating input control valve 150 is configured to provide a variety of orifice sizes, opening sizes or the like to control a flow rate of the input fluid into the reservoir 115. For instance, the modulating control valve provides one or more flow rates of the input fluid, including a range of flow rates, to the reservoir 115 based on a specified flow rate.

[0027] In some examples, the system 100 includes an overflow 160. The overflow 160 includes an opening in communication with the reservoir 115. The overflow 160 is configured to prevent the base fluid level within the reservoir 115 from exceeding a specified level, thereby preventing the reservoir 115 from overfilling with the base fluid.

[0028] In an example, the system 100 includes a drain 170 configured to substantially empty the reservoir 115 of the base fluid (e.g., for maintenance, transport or the like). The system 100 includes an output control valve 152, such as a modulating control valve. The output control valve 152 conditionally allows fluid to flow from the drain 170 at a fixed or variable flow rate. In an example, operation of the input control valve 150 and the output control valve 152 are coordinated by a controller or processor circuit to maintain a specified fluid level in the tank 110 or to maintain in the tank 110 fluid having particular characteristics (e.g., resistivity or conductivity characteristics).

[0029] FIG. 2 is a side view of one example of the probe assembly 120. As discussed herein, the one or more probes are configured to monitor the base fluid level in the reservoir 115 (shown in FIG. 1). In some examples, the oneor more probes include on / off sensors or float switches configured to monitor the base fluid level in the reservoir 115 (shown in FIG. 1). In some examples, the one or more probes include electrical characteristic instruments, such as an impedance sensor. In an example, the electrical characteristic instruments measure the impedance (e.g., resistance, conductivity, capacitance, inductance or the like) of the base fluid to monitor the base fluid level in the reservoir 115. In one example, a probe measures the capacitance or inductance of deionized water to monitor the base fluid level in the reservoir 115. In some examples, each probe includes a conductive tip and an insulated sheath. The conductive tip comprises an electrode that can be selectively excited by a controller.

[0030] In an example, the one or more probes include a conductance probe. In the examples shown in FIG. 1, FIG. 2. and FIG. 3, a plurality of conductance probes are used. In an example, the conductance probe is sheathed in an electrically insulative material and a tip of the conductance probe is exposed (e.g., sheathing is removed). The exposed tip of the probe provides one or more of the first or second probes. In an example, the first probe 121 is in communication with base fluid, such as water, contained in the reservoir 115. An electrical signal is transmitted to the first probe 121. The water contains impurities that allow the electrical signal to be transmitted from the first probe 121, through the water, and to a conductive surface or component of the tank 110 (shown in FIG. 1). In some examples, the electrical signal is used, such as by determining the resistance between the first probe 121 and the tank 110 (shown in FIG. 1), to determine (e.g., monitor) that the water level within the reservoir 115 is at a specified level (e.g., low level, normal operating level, or a full level).

[0031] In an example, the system 100 (shown in FIG. 1) uses existing components in a discrete fluid level control system including one or more sensors configured to detect a turbulated base fluid at one or more levels (e.g., heights, depths or the like) in the reservoir 115. In some examples, a fluid level sensor (e.g., the first probe 121 or the second probe 122) determines that the fluid level is at or above a particular height corresponding to the position of the probe tip. Stated another way, a fluidlevel probe detects the fluid at two positions: at or above the fluid level probe tip (e.g., in communication with the sensor), and below the fluid level probe tip (e.g., not in communication with the sensor).

[0032] In some examples, the reservoir 115 is a humidifier water tank. Boiling of a fluid (e.g., used to generate vapor for introduction to a stream of gas) creates turbulence in the fluid (e.g., waves, ripples, bubbles, or the like). With turbulence in the fluid, other devices used to measure discrete fluid levels sense periodic on and off conditions that frustrate the accurate measurement of the fluid level. In some examples, the turbulence in the base fluid is created by a mechanical device (e.g., a paddle, a pump, a oscillating or reciprocating mechanism, or the like) alone or in combination with a thermodynamic based turbulation, such as boiling. In an example where the turbulent state of the base fluid (e.g., water) results in a series of undulations (e.g., waves, bubbling surface or the like) on the surface of the base fluid, the height of the undulations vary depending on one or more of the boiling rate, mechanical turbulation or the like of the base fluid.

[0033] In the example of the discrete fluid level control systems described herein, turbulation of the fluid is used advantageously to accurately and precisely establish the fluid level (e.g., quantity, height, volume or the like) under dynamic conditions including evaporation, in flow, out flow, turbulation, boiling, or the like. More accurate and precise determination of the fluid level is achieved by sensing the fluid level over a period of time and under dynamic conditions. Stated another way, the fluid level of the turbulated base fluid can be established according to the levels measured using the one or more probes.

[0034] Referring again to FIG. 2, an example includes the first probe 121 and the second probe 122, and the first probe 121 is located at a first sensor location, such as a first elevation. The second probe 122 is located at a second sensor location, such as a second (higher) elevation. In an example, the second sensor location is different from the first sensor location. For instance, the first probe 121 differs in length with respect to the second probe 122. The fluid level probe assembly 120 discerns that the base fluid level is in one of three regions (e.g., at one or more levels, heights, depths orthe like). In the example provided below, the three regions include (but are not limited to) a first region 210, a second region 220, and a third region 230. In the first region 210, none of the probes (e.g., including the lowest elevation first probe 121) senses the base fluid (e.g., water). In some examples, the first region 210 is assigned a numerical value of 0 for fluid level indexing purposes. The second region 220 corresponds to one probe (e.g., the first probe 121) detecting the base fluid. In some examples, the second region 220 is assigned a numerical value of 1 for fluid level indexing. The third region 230 corresponds to two probes (e.g., the first probe 121 and the second probe 122) detecting the base fluid. In some examples, the third region 230 is assigned a numerical value of 2 for fluid indexing purposes.

[0035] In an example, the base fluid in the reservoir 115 (shown in FIG. 1) is turbulated. The level of the turbulated base fluid is measured to determine if additional fluid (e.g, the input fluid described with reference to FIG. 1) is specified for input to the reservoir 115. In some examples, measuring the level of the turbulated base fluid includes measuring a first level and a second level of the turbulated base fluid (e.g., a peak and trough of the turbulated fluid). In an example, measuring the first height and the second height of the turbulated base fluid includes sensing the turbulated base fluid is in the first region 210 (e.g., below a distal tip or electrode of the first probe 121). In another example, measuring the first height and the second height of the turbulated base fluid includes sensing the turbulated base fluid is in the second region 220 (e.g., between the tips of the first probe 121 and the second probe 122, or above the tip of the first probe 121 and below the tip of the second probe 122). In another example, measuring the first height and the second height of the turbulated base fluid includes sensing the turbulated base fluid is in the third region 230 (e.g., at or above a tip of the second probe 122).

[0036] FIG. 3 is a side view of the probe assembly 120 of FIG. 2 and a turbulated base fluid 300. An undulation of the turbulated base fluid has a wave midpoint 330 (e.g., a wave centerline) between the peak 320 and trough 310 of the wave. In some examples, the wave midpoint 330 corresponds to the base fluid level within the reservoir 115. In an examplewhere the wave midpoint 330 is located at the lower probe (e.g., at a distal tip 302 of the first probe 121), the fluid level is determined by detecting the turbulated base fluid at one or more heights in the reservoir 115 (shown in FIG. 1). The fluid level can be determined or sampled several times per unit time (e.g., per second, per minute, etc.) over the course of a time period (e.g., a sampling period, duty cycle or the like such as every 5, 10, 15, 20 seconds, a minute or the like).

[0037] In an example, the first region 210 (shown in FIG. 2) is assigned a numerical value of 0 for fluid level indexing. Similarly, the second region 220 and the third region 230 are assigned numerical values of 1 and 2, respectively. With the wave midpoint 330 coincident with the distal tip 302 of the first probe 121, the numerical values generated from the first probe 121 result in a roughly 50:50 ratio of sensing a numerical value of “1” (e.g., the first height) and sensing a numerical value of “0” (e.g., the second height). The average of those readings is approximately “0.5”. In another example, if the wave midpoint 330 height is not at the height of the distal tip 302 (is above or even below the first probe 121 because of contact by the wave crests) the numerical values range from 0 to 1 with a corresponding varying ratio. In yet another example, if the wave midpoint 330 height is proximate the height of the tip of the second probe 122, then the numerical values range from 0-2 (or 1-2 depending on the amplitude of the undulations) because at least the peak of the base fluid contacts the tip of the second probe 122.

[0038] In an example, a quantity of numerical values are equal to the number of readings that are taken in a sample period. For instance, if 20 samples are measured over a sample period of one second, data generated (numerical values as described above) are in increments of 1 / 20 seconds or 0.05 seconds. By increasing the sampling rate of the fluid sensor, the system 100 provides greater resolution and corresponding higher precision and accuracy of the fluid level determination. However, there can be a limit to the sampling rate based on, for example, an amplitude of the excitation signal used or an ionization (e.g., concentration) of the fluid in the tank.

[0039] As described herein, in some examples, the first height and the second height of the turbulated base fluid is measured by the probe assembly 120. In an example, measuring the first height or the second height of the turbulated base fluid includes measuring a first time period the turbulated base fluid is above the first probe 121 during a sample period. Additionally, measuring the first height or the second height of the turbulated base fluid also includes measuring a second time period the turbulated base fluid is below the second sensor 121 during the sample period. Further, measuring the first height or the second height of the turbulated base fluid also includes establishing one or more of the first height or the second height according to the measured first time period and second time period. In this example, the measuring of the first height or the second height is accomplished similarly to the aforementioned examples. However, in addition to establishing whether or not the fluid is in a region (e.g., the first region 210, the second region 220, or the third region 230), the apparatus evaluates the length of time that the fluid is within a particular region. Stated another way, the apparatus establishes the fluid level of a turbulated base fluid by determining the length of time the turbulated base fluid is sensed (and not sensed) by a fluid level sensor (e.g., the first probe 121).

[0040] In contrast to a system that measures discrete values (e.g., 0, 1, 2, or the like) with an ordinary sampling scheme, the system 100 can measure more precise and accurate values (e.g., 0.05, 0.45, 1.35, or the like). For example, if 100 readings are conducted over a sample period and 35 of those readings produced a numerical value of 2, and 65 of those readings produced a numerical value of 1, the average value of those readings is 1.35. In other words, the wave midpoint 330 of the turbulated base fluid is 35 percent between the first probe 121 and the second probe 122. In an example, the first probe 121 can be spaced several (e.g., ten) inches from a bottom of the tank 110 (shown in FIG. 1). The second probe 122 can be spaced from the first probe 121 by, e.g., one inch (e.g., the second sensor is eleven inches from the bottom of the tank 110). In this example, the reading of 1.35 signifies that the wave midpoint 330 is located at 10.35 inches from the bottom of the tank 110.

[0041] Various operations can be performed based on the range of numerical values determined or collected during the sample period. For example, the numerical values are inputs into a mathematical model that determines the fluid level. In other examples, the numerical values are inputs into proportion, integration, or derivative (“PID”) loop (or a combination thereof). The PID loop periodically determines an error value that is the difference between a process set point (e.g., the desired humidity in an environment or desired fluid level within a reservoir) and a process variable (e.g., the actual humidity in an environment or actual fluid level within a reservoir). The PID loop parameters are optimized to best minimize the error value. The resultant value computed by the PID loop is used to adjust a control variable. In one example, the control variable is an input signal into a control valve. In some examples, and as will be discussed further herein, the range of numerical values collected during the sample period arc used to create a turbulent surface parameter.

[0042] In an example, the first height and the second height of the turbulatcd base fluid is measured by the probe assembly 120. In another example, the measuring of the first height or the second height is established according to a proportion of the measured first time period to the second time period. Stated another way, the first or second height of the turbulated base fluid is determined by evaluating the amount of time that the fluid is within a particular region in comparison to the time that the fluid is within another region. The result of the comparison establishes the fluid level within the reservoir 115 (shown in FIG. 1). For example, and as shown in FIG. 3, the first probe 121 measures the height of the fluid level based on the waveform of the turbulated base fluid. In this example, the first probe 121 detects the fluid (e.g., the wave is at or above the first probe 121) around 50 percent of the period (e.g., of the wave, time interval, or the like) and accordingly does not detect the fluid the remaining 50 percent of the period (the fluid is below the sensor element). Based on the 50 / 50 proportion of the sensed heights and the location of the sensor element the system determines the fluid level (in this example) is accurately and precisely located at the fluid level shown in dashed lines. In other examples where the proportionchanges (e.g., 70 at or above and 30 below) fluid level is established at a corresponding proportional location above the first sensor. In still yet another example, the aforementioned examples for measuring the first or second height are performed repeatedly on an ongoing basis, and the output (determined height) is automatically updated based on the continued measurements.

[0043] FIG. 4 illustrates generally a block diagram of a water level detection system 400. The water level detection system 400 includes a probe assembly 402, a sensing circuit 404, and a control valve 414. The probe assembly 402 can comprise an example of the probe assembly 120. For example, the probe assembly 402 can include a first probe 410 (e.g., corresponding to or comprising the first probe 121) and a second probe 412 (e.g., corresponding to or comprising the second probe 122). In an example, the sensing circuit 404 includes a signal generator circuit 406 and a processor circuit 408. The control valve 414 can comprise one or more valves, such as the input control valve 150 and the output control valve 152 from the example of the system 100.

[0044] In an example, the sensing circuit 404 is coupled to the probe assembly 402. The signal generator circuit 406 can generate excitation signals for one or more probes of the probe assembly 402. The signal generator circuit 406 generates signals having various signal characteristics. For example, the signal generator circuit 406 can generate DC signals, DC pulse signals having various duty cycle characteristics, or AC signals, any of which can have various frequency or amplitude characteristics. In an example, the signal generator circuit 406 is configured to generate DC pulse signals for high-sensitivity detection of high-resistance water in a first mode, and AC signals for lower-sensitivity detection of lower-resistance water in a second mode.

[0045] The signal generator circuit 406 can adjust signal characteristics including frequency and duty cycle to fine-tune sensitivity within each operating mode. In the first mode, the signal generator circuit 406 provides DC pulse signals suitable for detecting water with resistance above approximately 50k . In the second mode, the signal generator circuit 406provides AC signals for detecting water with resistance below approximately 50kQ. In an example, the sensing circuit 404 comprises various circuitry that is configured to receive a DC pulse signal as a stimulus and, in response, provide an AC signal.

[0046] In the second mode, the AC signal at the probe tip allows for higher excitation voltages compared to DC mode without causing electrolysis effects in the measured water. In an example, in AC mode, excitation signal frequency and duty cycle characteristics can be adjusted to thereby allow the system to achieve different sensitivity levels using a particular or single set of circuit components. For example, the system can adjust the clock frequency or duty cycle to fine-tune sensitivity within a particular detection range, rather than (or in addition to) using component changes to achieve sensitivity adjustments.

[0047] The processor circuit 408 can be configured to measure probe voltages to determine water conductivity characteristics and control mode switching between the first and second modes. In an example, the processor circuit 408 calculates or determines a fluid concentration factor based on conductivity measurements over time to track mineral concentration changes in the tank fluid. When operating in the second mode, the processor circuit 408 can adjust sensitivity settings through the signal generator circuit 406 to discriminate between foam and bulk water (i.e., full probe tip submersion).

[0048] In an example, the probe assembly 402 includes the first probe 410 and second probe 412 arranged in proximity. The probes arc sequentially excited in a round-robin fashion with appropriate delays between excitations to manage ion distribution effects. The processor circuit 408 coordinates the sequential probe excitation timing with the signal generator circuit 406 based on detected water conductivity characteristics.

[0049] In an example, the control valve 414 regulates water addition and / or drainage based on a determination by the processor circuit 408 about tank fluid levels or fluid characteristics. The processor circuit 408 coordinates actuation of the control valve 414 based on detected water levels, calculated concentration factors, and current operating mode and sensitivity settings to maintain optimal system operation.

[0050] In an example, the processor circuit 408 is in communication with the fluid level probe assembly 402 and is responsible for determining the fluid level within the reservoir 115 (shown in FIG. 1). In another example, the processor circuit 408 is configured to control the flow rate of the input fluid through the input control valve 150 by communicating with the input control valve 150. In some examples, the controlling of the flow rate is proportional to the turbulent fluid surface parameter determined by the processor circuit 408. In some instances, graduating the introduction of the input fluid into the reservoir 115 includes or uses the processor circuit 408 to automatically control a valve opening and corresponding flow rates through the valve according to the established fluid level of the turbulated base fluid. In another example, the flow rate is controlled by the processor circuit 408 providing a control signal to the input control valve 150 that controls the valve opening and regulates the flow rate through the valve (c.g., based on the established fluid level). In one example, the processor circuit 408 comprises a portion of a programmable logic controller (“PLC”) or microprocessor.

[0051] FIG. 5 illustrates generally an example sensing circuit 500 for a water level detection system. The example sensing circuit 500 is configured to use one or more probes for dual-mode water level detection. The example sensing circuit 500 includes various switches that can be selectively actuated (e.g., in response to control signals from the processor circuit 408) to change an operating mode or sensitivity of the example sensing circuit 500. In an example, multiplexer circuitry (not shown) can be used to selectively introduce or remove various components from the signal paths and / or to change the values of various resistors or other components in the circuit.

[0052] The illustrated example of FIG. 5 shows the example sensing circuit 500 configured for a lower-sensitivity AC operating mode. In the lower-sensitivity AC operating mode, a first switch SI is in a first position, and a second switch S2 is in a first position, to thereby couple first and second series capacitors Cl and C2 into a probe signal path. The probe signal path extends from a probe input node where a probe voltage Vprobe can be measured. The probe connection point (Vprobe) interfaces with the probeassembly, with the circuit measuring voltage at this point to determine fluid presence and various fluid characteristics. The measured voltage serves as a surrogate for conductivity or resistivity measurements, with higher voltages indicating higher resistance (lower conductivity) water.

[0053] In an example, a clock signal (VGEN) provides a DC pulse signal that serves as an excitation signal source. For example, the signal generator circuit 406 from the water level detection system 400 can provide the clock signal. The signal generator circuit 406 can provide the clock signal with various frequency and / or magnitude characteristics. In a lower-sensitivity AC mode, the clock signal can have a frequency of approximately 1 kHz. In DC mode, the frequency can be less critical but can be selected to be high enough to maintain stable circuit operation.

[0054] The example sensing circuit 500 includes a first capacitor (Cl) that, when coupled into the probe signal path in AC mode, converts the clock signal VGEN into an AC signal at the probe input node. In an example, the first capacitor has a value of about 350nF. The first capacitor charges and discharges to create the alternating current used in the lower-sensitivity detection mode.

[0055] In an example, the example sensing circuit 500 includes a first comparator 502 and a second comparator 504. The comparators can be implemented using, for example, differential or operational amplifier circuits. The first comparator 502 can be configured to compare a probe voltage on the probe signal path to a specified threshold voltage to determine whether the probe is immersed in fluid. The second comparator 504 can comprise a portion of an output stage of the example sensing circuit 500 that is configured to provide an output signal Vo that indicates the fluid detection status or sensing result. In other words, the output stage can help provide a stable, logical output signal that indicates whether the probe is immersed in fluid or is not immersed in fluid.

[0056] The output stage includes an RC network (e.g., comprising R8 and C3). The RC network provides filtering and a specified settling time, such as between measurements. The settling time can increase at higher sensitivities, using longer excitation times in DC mode compared to AC mode.

[0057] The example sensing circuit 500 includes a bias generator circuit that sets a bias voltage or center voltage for the probe. In an example, the bias generator circuit comprises a voltage divider network that includes a first resistor R1 and a second resistor R2. The bias generator circuit can be coupled to a first input of the first comparator 502 and to the probe signal path. The second input of the first comparator 502 can be coupled to an adjustable reference voltage source. The reference voltage source can comprise a voltage divider network that includes a third resistor R3 and a fourth resistor R4. The values of the various resistors of the voltage divider networks can be dynamically adjusted depending on, for example, the operating mode or desired sensitivity of the example sensing circuit 500. For example, in the higher-sensitivity mode, the bias generator circuit can be configured to provide a bias voltage Vbias that is less than about IV, to help minimize electrolysis of the fluid to be measured.

[0058] In an example, the example sensing circuit 500 can be configured as follows for a higher-sensitivity DC operating mode. Vcc can be approximately 5 V. The first and second switches can be positioned oppositely to the illustrated example, to remove the series capacitors Cl and C2 from the probe signal path. The signal generator resistor RGEN can have a value of approximately 3 MO. Resistors R1 and R2 can have values of approximately 5 MO and 1 MQ respectively. Resistors R3 and R4 can have values of approximately 300 kQ and 60 kQ respectively. Resistors R5 and R6 can have values of approximately 50 kQ and 10 kQ respectively. Resistor R7 can be approximately 10 kQ, resistor R8 can be approximately 243 kQ, and C3 can be approximately 100 nF. Other values can similarly be used. In DC mode, the sensitivity or threshold comparison voltage can be changed, for example, by changing the value of one or more of the third and fourth resistors R3 and R4 in the voltage divider. The DC pulse operation enables placement of sensing circuit components at greater distances from the probe assembly, as parasitic capacitance from longer wire runs does not significantly impact measurement accuracy in this mode. This provides greater flexibility in system design and installation compared to AC-only sensing approaches.

[0059] In an example, the example sensing circuit 500 can be configured as follows for a lower-sensitivity AC operating mode. Vcc can be approximately 5 V. The first and second switches can be positioned as shown in the illustrated example to include the series capacitors Cl and C2 in the probe signal path. The signal generator resistor RGEN can have a value of approximately 10 kQ. Resistors R1 and R2 can have values of approximately 243 k and 190 kQ respectively. Resistors R3 and R4 can have values of approximately 100 kQ and 243 kQ respectively. Resistors R5 and R6 can have values of approximately 50 kQ and 10 kQ respectively. Resistor R7 can be approximately 10 kQ, resistor R8 can be approximately 243 kQ, and C3 can be approximately 100 nF. Other values can similarly be used. In AC mode, the sensitivity of the circuit can be adjusted by changing any one or more of the signal generator resistor RGEN, or one or more of the third and fourth resistors R3 and R4 in the voltage divider. Additionally or alternatively, in the AC mode, the sensitivity of the circuit can be adjusted by changing an amplitude, frequency, or duty cycle characteristic of the excitation signal or clock signal VGEN.

[0060] The specific component values and structure for the example sensing circuit 500 are provided for reference only. Various other components can be used, additionally or alternatively to those shown in the schematic, to further enhance operation or tuning of the sensing circuit.

[0061] FIG. 6 illustrates generally a first portion 600 of a first method for operating a water level detection system. FIG. 7 illustrates a second portion 700 of the first method for operating a water level detection system. The system can comprise, for example, one or more of the system 100, the water level detection system 400, or the example sensing circuit 500, among other components or features.

[0062] At initiation 602, the system can begin operation in a high sensitivity mode. This starting mode enables detection of high-resistance (low conductivity) purified water using DC pulse signals to excite a probe tip. In an example, the DC pulse signal is a 1 kHz signal that is delivered in 20 ms bursts, with approximately 100 ms between bursts.

[0063] At decision operation 604, the system performs an initial check to determine if the water level is low. If the level is not low at decision operation 604, then the system opens the drain at operation 606 and continues monitoring until a low level is detected. This drain sequence ensures proper starting conditions and allows verification of sensor operation. At decision operation 608, the system checks if the probe voltage reads high or low to verify proper sensor function. If the probe voltage does not read a low water level at decision operation 608, then the system identifies sensor contamination or malfunction at operation 610. This check prevents system operation with compromised sensors that could provide unreliable measurements.

[0064] When proper sensor operation is confirmed, the first method can continue at operation 612 with opening the fill valve. The system checks for fluid at the first probe at decision operation 614. If no fluid is detected, then the fill operation continues. The system can continuously monitor the first probe at decision operation 614 during the filling process.

[0065] At decision operation 614, in response to fluid being detected at the first probe, the fill valve closes at operation 616. The system then attempts to reduce sensitivity at operation 618 by switching to AC mode or adjusting component values. After reducing sensitivity, the system verifies the first probe is still sensing fluid at decision operation 620. If the probe no longer detects fluid after reducing sensitivity, then the system can revert to the prior sensitivity level at operation 622. This verification step ensures reliable level detection is maintained when changing sensitivity modes. After reverting to the prior sensitivity level at operation 622, the first method can continue at operation 702 (see FIG. 7).

[0066] At operation 702, the system can monitor fluid status in a relatively lower sensitivity mode (e.g., AC mode). At operation 704, the system is configured to calculate or determine a water concentration factor. This calculation compares current conductivity measurements to initial values to track mineral concentration changes.

[0067] In an example, the system determines the water concentration factor by tracking changes in water conductivity over time relative to initial values.The concentration factor represents how many times minerals in the water have concentrated compared to their starting concentrations.

[0068] In an example, concentration factor is calculated as a ratio between current conductivity measurements and initial conductivity measurements. For example, if the initial water conductivity corresponds to 10 parts per million of chlorides, a concentration factor of 5 would indicate the chloride concentration has increased to 50 parts per million.

[0069] This calculation enables the system to track mineral concentration independently of the absolute conductivity values. The concentration factor provides a normalized measurement that works across different source waters, whether starting with high-purity water or typical tap water. For example, with municipal water starting at approximately 1000 Q-cm resistance, after concentrating about 6 times through boiling, the system can calculate a concentration factor of 6 when measurements indicate approximately 166 -cm resistance.

[0070] The concentration factor can be used to trigger sensing mode or sensitivity changes and water cycling decisions. Using the previous example, if the system is configured with a predetermined or specified concentration factor limit of 5 to prevent chloride levels from exceeding 50 parts per million, then the system can initiate a drain cycle when measurements indicate the water has concentrated 5 times from its initial state. This provides proactive water cycling before mineral concentrations become problematic for system operation. In an example, the system (c.g., using the processor circuit 408 of the water level detection system 400) continuously updates the concentration factor calculation during operation in lower sensitivity modes to track progressive concentration of dissolved solids. This enables the system to maintain optimal operation by preventing excessive mineral buildup while also avoiding unnecessary water cycling.

[0071] Returning to the discussion of FIG. 7, at decision operation 706, the system checks if a concentration factor limit has been reached. When the concentration factor limit is reached, the system reduces sensitivity at operation 708 to maintain accurate measurements with higher conductivity water. The system then checks for fluid level status changes at decisionoperation 710 to verify the sensitivity adjustment has not compromised fluid detection.

[0072] At decision operation 710, if the fluid level status changes after reducing sensitivity, then the system reverts to the prior sensitivity level at operation 712. If no status change occurred, then the system checks the concentration factor limit at decision operation 714 to determine if water cycling is needed. When the concentration factor limit is reached and the system is not in high sensitivity mode, the tank is drained at operation 716 before returning to the start sequence at initiation 602 (see FIG. 6). This cycling prevents excessive mineral concentration while maintaining optimal system operation.

[0073] FIG. 8 illustrates generally an example of a second method 800 for changing modes of operation of a water level detection system. Although the example second method 800 depicts a particular sequence of operations, the sequence may be altered without departing from the scope of the present disclosure. For example, some of the operations depicted may be performed in parallel or in a different sequence that does not materially affect the function of the second method 800. In other examples, different components of an example device or system that implements the second method 800 may perform functions at substantially the same time or in a specific sequence.

[0074] At operation 802, the second method 800 includes using a sensing circuit operating in a first mode to apply DC pulse signals to one or more probes of a probe assembly, and the one or more probes arc disposed inside a water tank. This high-sensitivity DC mode enables detection of high-resistance water. In an example, the DC pulse signals are configured to maintain probe tip voltages below IV to prevent electrolysis. The DC pulse signals can be generated by the signal generator circuit 406, for example, and provided directly to one or more probes (e.g., in a round-robin manner). In an example, operation 802 can include configuring the sensing circuit to use particular resistors that set a threshold comparison point for a probe voltage, a bias voltage for a probe, or can include updating one or more characteristics of the stimulus signals used to excite a probe in the DC mode,such as DC pulse signal characteristics (e.g., frequency, magnitude, or burst or duty cycle characteristics).

[0075] At operation 804, the second method 800 includes receiving respective probe voltage measurements indicative of respective water conductivity characteristics of the water in the tank. The probe voltages serve as surrogate measurements for conductivity, with higher voltages indicating higher resistance water. These measurements are taken after appropriate settling times that increase at higher sensitivity levels to allow for proper circuit stabilization.

[0076] At operation 806, the second method 800 includes identifying an increase in water conductivity of the water in the tank based on the probe voltage measurements. As minerals concentrate during operation, the water conductivity increases (resistance decreases). The system monitors these changes by comparing voltage measurements over time to track conductivity trends.

[0077] At operation 808, the second method 800 includes, in response to identifying the increase in water conductivity, updating the sensing circuit for operation in a second mode. For example, at operation 808, when measurements indicate water resistance has decreased below approximately 50kQ, the sensing circuit switches to operation in a second lower-sensitivity AC mode. In an example, operation 808 can include configuring the sensing circuit to use particular resistors that set a threshold comparison point for a probe voltage, a bias voltage for a probe, or can include updating one or more characteristics of the stimulus signals used to excite a probe in the AC mode (e.g., frequency or magnitude characteristics).

[0078] At operation 810, the second method 800 includes applying an AC signal to a particular probe of the probe assembly and, in response, receiving a subsequent probe voltage measurement indicative of a subsequent water conductivity characteristic of the water. In an example, operation 810 includes routing a DC pulse signal from the signal generator circuit 406 through a 350nF series capacitor to provide an AC signal at one or more of the probes. The series capacitor charges and discharges to create alternating current at the probe tip, enabling measurements suitable for higherconductivity water. The system can receive subsequent probe voltage measurements that indicate updated water conductivity characteristics in this mode.

[0079] In an example, in the second mode, the system can discriminate between foam and bulk water by measuring probe voltages at different sensitivity settings. By reducing the reference resistor values in the example sensing circuit 500, for example, the system can be used to determine if voltage changes indicate foam (indicated by a probe maintaining a high voltage) or bulk water (dropping to low voltage) in coordination with a resistor value change.

[0080] In the second mode, the system discriminates between foam and bulk water (submersion) at the probe tip by looking for electrical characteristics that may indicate a foam structure instead of bulk water. Foam creates a three-dimensional matrix of water with mostly air / steam at its core, resulting in much higher electrical resistance compared to the bulk water it forms from. For example, if bulk water measures at approximately IkQ resistance at the probe tip when the tip is fully submerged in the bulk water, then foam from that same water can measure 50kQ. In an example, the system performs foam detection by adjusting one or more resistor valuc(s) in the sensing circuit. For example, the value of the signal generator resistor RGEN can be changed from approximately 10 kQ to between about 100 Q and 1 k . This reduction in resistance makes the circuit less sensitive, requiring a lower resistance path to ground to pull the probe voltage low. At this reduced sensitivity setting, foam may not provide enough conductivity to pull the voltage low, while bulk water will. The system determines foam presence when the probe voltage remains high after reducing sensitivity, and determines bulk water presence when the voltage drops low.

[0081] For example, with tap water at approximately 1000 Q resistance, foam detection can become important when the water concentrates about 6 times through boiling, reaching approximately 166 Q. The system can be configured to set its foam detection decision point around 200 Q in this lower resistance range. This enables reliable discrimination between foam and bulk water since foam will exhibit approximately an order of magnitudehigher resistance compared to the bulk water it forms from, even as mineral concentration increases during operation.

[0082] In an example, the system is configured to use round-robin sampling of multiple probes to obtain more accurate water level measurements through coordinated probe excitation and measurement timing. For example, the probes can be excited sequentially with specific delays between excitations to manage ion distribution effects that could impact measurement accuracy.

[0083] When operating in either mode, the system coordinates probe excitation timing based on water conductivity characteristics. For higher conductivity water, shorter delays can be used between probe excitations. For lower conductivity water, longer delays can be used to allow proper settling time between measurements. The sequential excitation helps prevent interference between adjacent probes while ensuring accurate fluid or level detection.

[0084] FIG. 9 illustrates generally an example of a third method 900 that includes using a probe assembly to provide a fluid level indication of a fluid in a container. In an example, the third method 900 includes an example of round-robin sampling of multiple probes. Although the example third method 900 depicts a particular sequence of operations, the sequence may be altered without departing from the scope of the present disclosure. For example, some of the operations depicted may be performed in parallel or in a different sequence that docs not materially affect the function of the third method 900. In other examples, different components of an example device or system that implements the third method 900 may perform functions at substantially the same time or in a specific sequence.

[0085] At operation 902, the third method 900 includes generating a first excitation signal using a signal generator circuit, such as the signal generator circuit 406 from the water level detection system 400 of FIG. 4. In an example, generating the first excitation signal includes generating a signal burst, and the signal burst comprises a pulse signal having a pulse frequency of at least 1 kHz, and a burst duration of at least 10 ms.

[0086] At operation 904, the third method 900 includes providing the first excitation signal to a first fluid level probe.

[0087] At operation 906, the third method 900 includes measuring a first voltage from the first fluid level probe. The operation 906 can be performed after a first settling time and while the first fluid level probe receives the first excitation signal.

[0088] At operation 908, the third method 900 includes removing the first excitation signal from the first fluid level probe.

[0089] At operation 910, the third method 900 includes generating a second excitation signal using the signal generator circuit.

[0090] At operation 912, the third method 900 includes providing the second excitation signal to a second fluid level probe. The first and second fluid level probes can be the same probe or they can comprise different probes of a probe assembly, such as the probe assembly 120 of the system 100. In an example, operation 912 can be performed in response to removing the first excitation signal from the first fluid level probe at operation 908 and after a blanking time. In an example, the blanking time is at least as long as the burst duration. In some examples, the blanking time is several times longer than the burst duration.

[0091] At operation 914, the third method 900 includes measuring a second voltage from the second fluid level probe. The operation 914 can be performed after a second settling time and while the second fluid level probe receives the second excitation signal.

[0092] At operation 916, the third method 900 includes providing a fluid level indication of the fluid in the container based on the measured first and second voltages from operation 906 and operation 914, respectively. Tn an example, the operation 916 includes providing an indication that a fluid level is at or above a location of a distal electrode of the first fluid level probe. In an example, the operation 916 includes providing an indication that the fluid level is between the location of the distal electrode of the first fluid level probe and a location of a distal electrode of the second fluid level probe. In a further example, the operation 916 includes providing an indication that thefluid level is at or above a location of a distal electrode of the second fluid level probe.

[0093] The following Examples provide a non-limiting overview of, among other things, the detection systems (e.g., for water, liquid, or other fluids), methods, and techniques discussed herein.

[0094] Example 1 is a water level detection system comprising: a probe assembly; a sensing circuit coupled to the probe assembly and configured to: operate in a first mode for detecting high-resistance water by applying a DC pulse signal to one or more probes of the probe assembly; operate in a second mode for detecting lower-resistance water by applying an AC signal to the one or more probes of the probe assembly; and switch between the first and second modes based on detected water resistivity characteristics.

[0095] In Example 2, the subject matter of Example 1 optionally includes the sensing circuit is configured to operate in the second mode by applying the DC pulse signal through a series capacitor to generate the AC signal at the probe.

[0096] In Example 3, the subject matter of one or more of Examples 1-2 optionally includes the sensing circuit is configured to switch from operation in the first mode to operation to the second mode in response to a detected change in probe voltage measured in the first mode and using a first probe of the probe assembly.

[0097] In Example 4, the subject matter of one or more of Examples 1-3 optionally includes the sensing circuit is configured to: measure a probe voltage from a first probe of the probe assembly in the first mode; switch from the first mode to the second mode when the measured probe voltage indicates water resistivity is below approximately 50k ; and maintain operation in the first mode when the measured probe voltage indicates water resistivity is above approximately 50kQ.

[0098] In Example 5, the subject matter of one or more of Examples 1-4 optionally includes the sensing circuit includes a reference resistor network configured to set a water level detection sensitivity in each mode.

[0099] In Example 6, the subject matter of Example 5 optionally includes the sensing circuit is configured to change the water level detection sensitivity by changing at least one of a resistor in the reference resistor network, a duty cycle of the DC pulse signal, a duty cycle of the AC signal, and a frequency of the AC signal.

[0100] In Example 7, the subject matter of one or more of Examples 5-6 optionally includes, in the second mode, the sensing circuit is configured to: measure a first voltage at a first probe of the probe assembly and determine if the first voltage is less than a first reference voltage to indicate presence of bulk water; measure a second voltage at the first probe and determine if the second voltage is less than a second reference voltage to indicate presence of bulk water; determine presence of foam at the first probe when the first probe voltage exceeds the first reference voltage and the second probe voltage exceeds the second reference voltage, and determine presence of bulk water at the first probe when the first probe voltage exceeds the first reference voltage and the second probe voltage is less than the second reference voltage.

[0101] In Example 8, the subject matter of one or more of Examples 1-7 optionally includes a processor circuit configured to determine a concentration factor of detected water in the second mode of operation.

[0102] In Example 9, the subject matter of Example 8 optionally includes the processor circuit is configured to determine the concentration factor based on; an initial resistivity measurement of the water; a subsequent resistivity measurement of the water; and a ratio between the resistivity measurements, wherein the ratio indicates how many times minerals have concentrated relative to initial values such that if the initial resistivity corresponds to X parts per million of a mineral, the concentration factor equals N when the subsequent resistivity measurement indicates mineral concentration has reached N*X parts per million.

[0103] In Example 10, the subject matter of one or more of Examples 8-9 optionally includes the processor circuit is configured to: at a first time, determine an initial water level detection status; at a later second time, determine the concentration factor exceeds a predetermined limit; switch thesensing circuit to a lower sensitivity mode in response to the concentration factor exceeding the predetermined limit; determine a subsequent water level detection status after switching the sensitivity mode; and in response to the subsequent water level detection status differing from the initial water level detection status, switch the sensing circuit to a higher sensitivity mode.

[0104] In Example 11, the subject matter of one or more of Examples 1-10 optionally includes the probe assembly comprises two or more probes arranged in proximity to each other; and the sensing circuit is configured to sequentially excite each probe in a round-robin fashion with a predetermined delay between sequential probe excitations.

[0105] In Example 12, the subject matter of Example 11 optionally includes the sensing circuit is configured to determine water presence based on measurements from all of the probes.

[0106] In Example 13, the subject matter of one or more of Examples 11-12 optionally includes the predetermined delay between sequential probe excitations is based on water resistivity characteristics of detected water.

[0107] Example 14 is a method of level detection of water in a tank, the method comprising: using a sensing circuit operating in a first mode, applying DC pulse signals to one or more probes of a probe assembly and, in response, receiving respective probe voltage measurements indicative of respective water resistivity characteristics of the water in the tank; identifying a decrease in water resistivity of the water in the tank based on the probe voltage measurements; and in response to identifying the decrease in water resistivity, and using the sensing circuit operating in a second mode, applying an AC signal to a particular probe of the probe assembly and, in response, receiving a subsequent probe voltage measurement indicative of a subsequent water resistivity characteristic of the water.

[0108] In Example 15, the subject matter of Example 14 optionally includes operating in the second mode including applying a DC pulse signal through a capacitor to generate the AC signal.

[0109] In Example 16, the subject matter of one or more of Examples 14-15 optionally includes setting a water level detection sensitivity of the sensing circuit using a reference resistor network.

[0110] In Example 17, the subject matter of Example 16 optionally includes changing the water level detection sensitivity of the sensing circuit by changing at least one of: a resistor in the reference resistor network, a duty cycle of the DC pulse signal, a duty cycle of the AC signal, or a frequency of the AC signal.

[0111] In Example 18, the subject matter of one or more of Examples 14- 17 optionally includes, in the second mode: measuring a first voltage at a first probe of the probe assembly and determining if the first voltage is less than a first reference voltage to indicate presence of bulk water; measuring a second voltage at the first probe and determining if the second voltage is less than a second reference voltage to indicate presence of bulk water; determining presence of foam at or near the first probe when the first voltage exceeds the first reference voltage and the second voltage exceeds the second reference voltage; and determining presence of bulk water when the first voltage exceeds the first reference voltage and the second voltage is less than the second reference voltage.

[0112] In Example 19, the subject matter of one or more of Examples 14- 18 optionally includes, in the second mode, determining a concentration factor of the water in the tank, wherein the concentration factor is based on resistivity measurements of the water over time.

[0113] In Example 20, the subject matter of one or more of Examples 14- 19 optionally includes, in at least one of the first and second modes, sequentially exciting two or more probes of the probe assembly with a specified delay between excitations.

[0114] Example 21 is a method of measuring fluid characteristics of a fluid in a container using at least first and second fluid level probes of a fluid level probe assembly, wherein the first and second fluid probes extend from a common reference plane into the container by different respective amounts, the method comprising: generating, using a signal generator circuit, a first excitation signal; providing the first excitation signal to thefirst fluid level probe; after a first settling time and while the first fluid level probe receives the first excitation signal, measuring a first voltage from the first fluid level probe; removing the first excitation signal from the first fluid level probe; generating, using the signal generator circuit, a second excitation signal; in response to removing the first excitation signal from the first fluid level probe and after a blanking time, providing the second excitation signal to the second fluid level probe; after a second settling time and while the second fluid level probe receives the second excitation signal, measuring a second voltage from the second fluid level probe; and providing a fluid level indication of the fluid in the container based on the measured first and second voltages.

[0115] In Example 22, the subject matter of Example 21 optionally includes generating the first excitation signal including generating a signal burst, wherein the signal burst comprises a pulse signal having a pulse frequency of at least 1 kHz, and a burst duration of at least 10 ms.

[0116] In Example 23, the subject matter of Example 22 optionally includes the burst duration is about 20 ms.

[0117] In Example 24, the subject matter of one or more of Examples 22- 23 optionally includes a duration of the blanking time is at least as long as the burst duration.

[0118] In Example 25, the subject matter of one or more of Examples 22- 24 optionally includes a duration of the blanking time is at least twice as long as the burst duration.

[0119] In Example 26, the subject matter of one or more of Examples 21- 25 optionally includes providing the fluid level indication including providing an indication that the fluid level is at or above a location of a distal electrode of the first fluid level probe.

[0120] In Example 27, the subject matter of Example 26 optionally includes providing the fluid level indication including providing an indication that the fluid level is between the location of the distal electrode of the first fluid level probe and a location of a distal electrode of the second fluid level probe.

[0121] In Example 28, the subject matter of one or more of Examples 26- 27 optionally includes providing the fluid level indication including providing an indication that the fluid level is at or above a location of a distal electrode of the second fluid level probe.

[0122] In Example 29, the subject matter of one or more of Examples 21- 28 optionally includes providing the fluid level indication including determining the first voltage or the second voltage indicates the corresponding fluid level probe is less than fully submerged in the fluid.

[0123] In Example 30, the subject matter of one or more of Examples 21- 29 optionally includes providing the fluid level indication including determining the first voltage or the second voltage indicates the corresponding fluid level probe is fully submerged in the fluid.

[0124] In Example 31, the subject matter of one or more of Examples 21- 30 optionally includes the fluid in the container is water having a resistivity of at least 10 megaohm-cm.

[0125] Example 32 is at least one machine-readable medium including instructions that, when executed by processing circuitry, cause the processing circuitry to perform operations to implement of any of one or more of Examples 1-31.

[0126] Example 33 is an apparatus comprising means to implement of any of one or more of Examples 1-31.

[0127] Example 34 is a system to implement of any of one or more of Examples 1-31.

[0128] Example 35 is a method to implement of any of one or more of Examples 1-31.

[0129] Each of these non-limiting examples or embodiments can stand on its own or can be combined in various permutations or combinations with one or more of the other examples or embodiments discussed herein.

[0130] This detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as“examples.” Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. The present inventors contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), cither with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein.

[0131] In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.”

[0132] In the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. arc used merely as labels, and are not intended to impose numerical requirements on their objects.

[0133] Method examples described herein can be machine or computer-implemented at least in part. Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code may form portions of computer program products. Such instructions can be read and executed by one or more processors to enable performance of operations comprising a method, for example. The instructions are in any suitable form, such as but notlimited to source code, compiled code, interpreted code, executable code, static code, dynamic code, and the like.

[0134] Further, in an example, the code can be tangibly stored on one or more volatile, non-transitory, or non-volatile tangible computer-readable media, such as during execution or at other times. Examples of these tangible computer-readable media can include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like.

[0135] The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following statements (aspects) arc hereby incorporated into the Detailed Description as examples or embodiments, with each standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations.

Claims

CLAIMSWhat is claimed is:

1. A water level detection system comprising:a probe assembly;a sensing circuit coupled to the probe assembly and configured to: operate in a first mode for detecting high-resistance water by applying a DC pulse signal to one or more probes of the probe assembly:operate in a second mode for detecting lower-resistance water by applying an AC signal to the one or more probes of the probe assembly; andswitch between the first and second modes based on detected water resistivity characteristics.

2. The water level detection system of claim 1, wherein the sensing circuit is configured to operate in the second mode by applying the DC pulse signal through a series capacitor to generate the AC signal at the probe.

3. The water level detection system of claim 1, wherein the sensing circuit is configured to switch from operation in the first mode to operation to the second mode in response to a detected change in probe voltage measured in the first mode and using a first probe of the probe assembly.

4. The water level detection system of claim 1, wherein the sensing circuit is configured to:measure a probe voltage from a first probe of the probe assembly in the first mode;switch from the first mode to the second mode when the measured probe voltage indicates water resistivity is below approximately 50kQ; and maintain operation in the first mode when the measured probe voltage indicates water resistivity is above approximately 50k .

5. The water level detection system of claim 1, wherein the sensing circuit includes a reference resistor network configured to set a water level detection sensitivity in each mode.

6. The water level detection system of claim 5, wherein the sensing circuit is configured to change the water level detection sensitivity by changing at least one of a resistor in the reference resistor network, a duty cycle of the DC pulse signal, a duty cycle of the AC signal, and a frequency of the AC signal.

7. The water level detection system of claim 5, wherein, in the second mode, the sensing circuit is configured to:measure a first voltage at a first probe of the probe assembly and determine if the first voltage is less than a first reference voltage to indicate presence of bulk water;measure a second voltage at the first probe and determine if the second voltage is less than a second reference voltage to indicate presence of bulk water;determine presence of foam at the first probe when the first probe voltage exceeds the first reference voltage and the second probe voltage exceeds the second reference voltage, anddetermine presence of bulk water at the first probe when the first probe voltage exceeds the first reference voltage and the second probe voltage is less than the second reference voltage.

8. The water level detection system of claim 1, comprising a processor circuit configured to determine a concentration factor of detected water in the second mode of operation.

9. The water level detection system of claim 8, wherein the processor circuit is configured to determine the concentration factor based on:an initial resistivity measurement of the water;a subsequent resistivity measurement of the water; anda ratio between the resistivity measurements, wherein the ratio indicates how many times minerals have concentrated relative to initialvalues such that if the initial resistivity corresponds to X parts per million of a mineral, the concentration factor equals N when the subsequent resistivity measurement indicates mineral concentration has reached N*X parts per million.

10. The water level detection system of claim 8, wherein the processor circuit is configured to:at a first time, determine an initial water level detection status; at a later second time, determine the concentration factor exceeds a predetermined limit;switch the sensing circuit to a lower sensitivity mode in response to the concentration factor exceeding the predetermined limit;determine a subsequent water level detection status after switching the sensitivity mode; andin response to the subsequent water level detection status differing from the initial water level detection status, switch the sensing circuit to a higher sensitivity mode.

11. The water level detection system of claim 1, wherein:the probe assembly comprises two or more probes arranged in proximity to each other; andthe sensing circuit is configured to sequentially excite each probe in a round-robin fashion with a predetermined delay between sequential probe excitations.

12. The water level detection system of claim 11, wherein the sensing circuit is configured to determine water presence based on measurements from all of the probes.

13. The water level detection system of claim 11, wherein the predetermined delay between sequential probe excitations is based on water resistivity characteristics of detected water.

14. A method of level detection of water in a tank, the method comprising:using a sensing circuit operating in a first mode, applying DC pulse signals to one or more probes of a probe assembly and, in response, receiving respective probe voltage measurements indicative of respective water resistivity characteristics of the water in the tank;identifying a decrease in water resistivity of the water in the tank based on the probe voltage measurements; andin response to identifying the decrease in water resistivity, and using the sensing circuit operating in a second mode, applying an AC signal to a particular probe of the probe assembly and, in response, receiving a subsequent probe voltage measurement indicative of a subsequent water resistivity characteristic of the water.

15. The method of claim 14, wherein operating in the second mode includes applying a DC pulse signal through a capacitor to generate the AC signal.

16. The method of claim 14, comprising setting a water level detection sensitivity of the sensing circuit using a reference resistor network.

17. The method of claim 16, comprising changing the water level detection sensitivity of the sensing circuit by changing at least one of: a resistor in the reference resistor network, a duty cycle of the DC pulse signal, a duty cycle of the AC signal, or a frequency of the AC signal.

18. The method of claim 14, comprising, in the second mode:measuring a first voltage at a first probe of the probe assembly and determining if the first voltage is less than a first reference voltage to indicate presence of bulk water;measuring a second voltage at the first probe and determining if the second voltage is less than a second reference voltage to indicate presence of bulk water;determining presence of foam at or near the first probe when the first voltage exceeds the first reference voltage and the second voltage exceeds the second reference voltage; anddetermining presence of bulk water when the first voltage exceeds the first reference voltage and the second voltage is less than the second reference voltage.

19. The method of claim 14, comprising, in the second mode, determining a concentration factor of the water in the tank, wherein the concentration factor is based on resistivity measurements of the water over time.

20. The method of claim 14, comprising, in at least one of the first and second modes, sequentially exciting two or more probes of the probe assembly with a specified delay between excitations.

21. A method of measuring fluid characteristics of a fluid in a container using at least first and second fluid level probes of a fluid level probe assembly, wherein the first and second fluid probes extend from a common reference plane into the container by different respective amounts, the method comprising:generating, using a signal generator circuit, a first excitation signal; providing the first excitation signal to the first fluid level probe; after a first settling time and while the first fluid level probe receives the first excitation signal, measuring a first voltage from the first fluid level probe;removing the first excitation signal from the first fluid level probe; generating, using the signal generator circuit, a second excitation signal;in response to removing the first excitation signal from the first fluid level probe and after a blanking time, providing the second excitation signal to the second fluid level probe;after a second settling time and while the second fluid level probe receives the second excitation signal, measuring a second voltage from the second fluid level probe; andproviding a fluid level indication of the fluid in the container based on the measured first and second voltages.

22. The method of claim 21, wherein generating the first excitation signal includes generating a signal burst, wherein the signal burst comprises a pulse signal having a pulse frequency of at least 1 kHz, and a burst duration of at least 10 ms.

23. The method of claim 22, wherein the burst duration is about 20 ms.

24. The method of claim 22, wherein a duration of the blanking time is at least as long as the burst duration.

25. The method of claim 22, wherein a duration of the blanking time is at least twice as long as the burst duration.

26. The method of claim 21, wherein providing the fluid level indication includes providing an indication that the fluid level is at or above a location of a distal electrode of the first fluid level probe.

27. The method of claim 26, wherein providing the fluid level indication includes providing an indication that the fluid level is between the location of the distal electrode of the first fluid level probe and a location of a distal electrode of the second fluid level probe.

28. The method of claim 26, wherein providing the fluid level indication includes providing an indication that the fluid level is at or above a location of a distal electrode of the second fluid level probe.

29. The method of claim 21, wherein providing the fluid level indication includes determining the first voltage or the second voltage indicates the corresponding fluid level probe is less than fully submerged in the fluid.

30. The method of claim 21, wherein providing the fluid level indication includes determining the first voltage or the second voltage indicates the corresponding fluid level probe is fully submerged in the fluid.

31. The method of claim 21, wherein the fluid in the container is water having a resistivity of at least 10 megaohm-cm.

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