阅读说明：本技术 双极性互电容式液体感测 (Bipolar mutual capacitance liquid sensing ) 是由 黄涛 高翔 于 2019-04-22 设计创作，主要内容包括：本发明题为“双极性互电容式液体感测”。本发明提供一种液位感测控制器,其包括用于生成激励信号的信号发生器电路。所述控制器还包括用于将所述激励信号的反相路由到第一电容器的第一极电极的连接件。所述第一极电极耦合到用于保持液体的容器。所述控制器还包括用于将所述激励信号路由到第二电容器的第二极电极的连接件。所述第二正极电极耦合到所述容器。所述控制器还包括与感测电极的连接件,用于与所述第一极电极一起形成所述第一电容器并且与所述第二极电极一起形成所述第二电容器。所述控制器还包括测量电路,所述测量电路被配置为测量感测电极处的电荷并且基于所测量的电荷来确定所述容器中的液体是否已经达到所述第二极电极的液位。(The invention provides a bipolar mutual capacitance type liquid sensing. A liquid level sensing controller includes a signal generator circuit for generating an excitation signal. The controller further comprises a connection for routing an inverse 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 positive electrode is coupled to the container. The controller further comprises a connection to a sensing electrode for forming the first capacitor with the first pole electrode and the second capacitor with the second pole electrode. The controller further includes a measurement circuit configured to measure the charge at the sensing electrode and determine whether the liquid in the container has reached the level of the second pole electrode based on the measured charge.)

1. A liquid level sensing controller comprising:

a signal generator circuit configured to generate an excitation signal;

a first connection configured to route an inverse of the excitation signal to a first pole electrode of a first capacitor, the first pole electrode coupled to a container configured to hold a liquid;

a second connection configured to route the excitation signal to a second positive electrode of a second capacitor, the second positive electrode coupled to the container;

a third connection to a sense electrode configured to form the first capacitor with the first pole electrode and the second capacitor with the second pole electrode; and

a measurement circuit configured to measure the charge at the third connection and determine whether the liquid in the container has reached the level of the second pole electrode based on the measured charge;

wherein the polarity of the first pole electrode is opposite to the polarity of the second pole electrode.

2. The level sensing controller of claim 1, wherein the charge at the third connection is indicative of a relative capacitance between the first capacitor and the second capacitor.

3. The level sensing controller of claim 1, wherein the measurement circuit is configured to determine that the liquid in the container has reached the level of the first pole electrode based on a change in relative capacitance between the first capacitor and the second capacitor based on the charge at the third connection.

4. The liquid level sensing controller of claim 1, further comprising a fourth connection to a third pole electrode of a third capacitor, the third pole electrode coupled to the container, wherein:

the second connector is further configured to:

routing the excitation signal to the second pole electrode of the second capacitor when the proximity of the liquid of the container to the second pole electrode is to be checked; and is

Routing a ground signal to the second pole electrode of the second capacitor when the proximity of the liquid of the container to the third pole electrode is to be checked; and is

The fourth connection is configured to:

routing the excitation signal to the third pole electrode of the third capacitor when the proximity of the liquid of the container to the third pole electrode is to be checked; and is

Routing a ground signal to the third pole electrode of the third capacitor when proximity of liquid of the container to the second pole electrode is to be checked.

5. The liquid level sensing controller of claim 4, wherein the sensing electrode is further configured to form the third capacitor with the third pole electrode.

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

7. A method for sensing a liquid level, comprising:

generating an excitation signal;

routing, at a first connection, an inverse of the excitation signal to a first pole electrode of a first capacitor, the first pole electrode coupled to a container configured to hold a liquid;

routing the excitation signal to a second positive electrode of a second capacitor at a second connection, the second positive electrode coupled to the container;

forming the first capacitor with the first pole electrode and the sense electrode at a third connection to the sense electrode;

forming the second capacitor with the second pole electrode and the sense electrode;

measuring the charge at the third connection; and

determining whether the liquid in the container has reached the level of the second pole electrode based on the measured charge;

wherein the polarity of the first pole electrode is opposite to the polarity of the second pole electrode.

8. The method of claim 7, wherein the charge at the third connection represents a relative capacitance between the first capacitor and the second capacitor.

9. The method of claim 7, further comprising determining that the liquid in the container has reached the level of the first pole electrode based on a change in relative capacitance between the first capacitor and the second capacitor based on the charge at the third connection.

10. The method of claim 9, further comprising:

coupling a third pole electrode of a third capacitor to the container through a fourth connection with the third pole electrode;

by the second connecting member:

routing the excitation signal to the second pole electrode of the second capacitor when the proximity of the liquid of the container to the second pole electrode is to be checked; and is

Routing a ground signal to the second pole electrode of the second capacitor when the proximity of the liquid of the container to the third pole electrode is to be checked; and by the fourth connection:

routing the excitation signal to the third pole electrode of the third capacitor when the proximity of the liquid of the container to the third pole electrode is to be checked; and is

Routing a ground signal to the third pole electrode of the third capacitor when proximity of liquid of the container to the second pole electrode is to be checked.

11. The method of claim 10, further comprising forming the third capacitor with the sensing electrode and the third pole electrode.

12. The method of claim 10, further comprising providing the first pole electrode by coupling the first pole electrode to the container outside of a possible range of the liquid.

13. A system, comprising:

an electrode assembly including a sensing electrode, a first pole electrode of a first capacitor, and a second pole electrode of a second capacitor, the electrode assembly coupled to a container configured to hold a liquid;

a signal generator circuit configured to generate an excitation signal;

a first connection configured to route an inverse of the excitation signal to the first pole electrode of the first capacitor;

a second connection configured to route the excitation signal to the second pole electrode of the second capacitor;

a third connection to the sense electrode, the sense electrode configured to form the first capacitor with the first pole electrode and the second capacitor with the second pole electrode; and

a measurement circuit configured to measure the charge at the third connection and determine whether the liquid in the container has reached the level of the second pole electrode based on the measured charge;

wherein the polarity of the first pole electrode is opposite to the polarity of the second pole electrode.

14. The system of claim 1, wherein the charge at the third connection represents a relative capacitance between the first capacitor and the second capacitor.

15. The system of claim 1, wherein the measurement circuit is configured to determine that the liquid in the container has reached the level of the first pole electrode based on a change in relative capacitance between the first capacitor and the second capacitor based on the charge at the third connection.

16. The system of claim 1, further comprising a fourth connection to a third pole electrode of a third capacitor, the third pole electrode included in the electrode assembly, wherein:

the second connector is further configured to:

routing the excitation signal to the second pole electrode of the second capacitor when the proximity of the liquid of the container to the second pole electrode is to be checked; and is

Routing a ground signal to the second pole electrode of the second capacitor when the proximity of the liquid of the container to the third pole electrode is to be checked; and the fourth connection is configured to:

routing the excitation signal to the third pole electrode of the third capacitor when the proximity of the liquid of the container to the third pole electrode is to be checked; and is

Routing a ground signal to the third pole electrode of the third capacitor when proximity of liquid of the container to the second pole electrode is to be checked.

17. The system of claim 16, wherein the sensing electrode is further configured to form the third capacitor with the third pole electrode.

18. The system of claim 16, wherein the first pole electrode is coupled to the container outside of a possible range of the liquid.

Technical Field

The present disclosure relates to liquid level sensing, and more particularly, to dual polarity mutual capacitive liquid sensing.

Background

Various techniques exist for sensing the level of liquid in a container. The liquid is sensed using a contact or mechanical sensor, an optical sensor for observing the liquid level, an inductive sensor measuring the electromagnetic induction generated by the liquid, a hall effect sensor measuring the magnetic field generated by the liquid, and a capacitive sensor.

Capacitive sensors for measuring liquid levels include self-capacitance sensors and unipolar mutual capacitance sensors. However, the inventors of embodiments of the present disclosure have found that these capacitive sensors drift with environmental conditions such as humidity or temperature. Thus, the trigger may be caused by a liquid level change or an environmental change. These capacitive sensors need to reference a reference value when water does not cover the sensing area and calibration is required. Furthermore, these capacitive sensors cannot discern the initial state of the sensor, so it can be assumed that the sensor is not triggered at start-up. Embodiments of the present disclosure address these shortcomings of other solutions discovered by the inventors of these embodiments.

Disclosure of Invention

Embodiments of the present disclosure include a liquid level sensing controller. The controller may include a signal generator circuit configured to generate the excitation signal. The controller may include a first connection configured to route an inverse of the excitation signal to a first pole electrode of a first capacitor, the first pole electrode coupled to a container configured to hold a liquid. The controller may include a second connection configured to route the excitation signal to a second positive electrode of the second capacitor, the second positive electrode coupled to the container. The controller may include a third connection to the sensing electrode. The sensing electrode may be configured to form a first capacitor with the first pole electrode and a second capacitor with the second pole electrode. The controller may include a measurement circuit configured to measure the charge at the third connection and determine whether the liquid in the container has reached the level of the second pole electrode based on the measured charge. The polarity of the first pole electrode may be opposite to the polarity of the second pole electrode.

Embodiments of the present disclosure may include a method of sensing a liquid level. The method may include generating an excitation signal. The method may include routing an inverse phase of the excitation signal to a first pole electrode of a first capacitor at a first connection, the first pole electrode coupled to a container configured to hold a liquid. The method may include routing the excitation signal to a second positive electrode of a second capacitor at a second connection, the second positive electrode coupled to the container. The method may include forming a first capacitor with the first pole electrode and the sense electrode at a third connection to the sense electrode. The method may include forming a second capacitor with the second pole electrode and the sensing electrode, measuring a charge at the third connection, and determining whether the liquid in the container has reached a level of the second pole electrode based on the measured charge. The polarity of the first pole electrode is opposite to the polarity of the second pole electrode.

Drawings

Fig. 1 is an illustration of an exemplary system for bipolar mutual capacitive liquid sensing, according to an embodiment of the present disclosure.

Fig. 2 is a more detailed illustration of an electrode assembly for bipolar mutual capacitive liquid sensing, according to an embodiment of the present disclosure.

Fig. 3 is a more detailed illustration of a controller for bipolar mutual capacitive liquid sensing, according to an embodiment of the present disclosure.

Fig. 4 is an illustration of a method for bipolar mutual capacitive liquid sensing, in accordance with an embodiment of the present disclosure.

Detailed Description

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

In combination with any of the above embodiments, the charge at the third connection may represent the relative capacitance between the first capacitor and the second capacitor. In combination with any of the above embodiments, the measurement circuit is configured to determine that the liquid in the container has reached the level of the first pole electrode based on a change in relative capacitance between the first capacitor and the second capacitor based on the charge at the third connection. In combination with any of the above embodiments, the controller further comprises a fourth connection to a third pole electrode of a third capacitor, the third pole electrode coupled to the container. The second connector may be further configured to: the excitation signal is routed to the second pole electrode of the second capacitor when the liquid of the container is to be checked for proximity to the second pole electrode, and the ground signal is routed to the second pole electrode of the second capacitor when the liquid of the container is to be checked for proximity to the third pole electrode. In combination with any of the above embodiments, the fourth connector is configured to: the excitation signal is routed to the third pole electrode of the third capacitor when the proximity of the liquid of the container to the third pole electrode is to be checked, and the ground signal is routed to the third pole electrode of the third capacitor when the proximity of the liquid of the container to the second pole electrode is to be checked. In combination with any of the above embodiments, the sensing electrode is further configured to form a third capacitor with the third pole electrode. In combination with any of the above embodiments, the first pole electrode may be coupled to the container outside the possible range of liquids. In combination with any of the above embodiments, the excitation signal applied to the second capacitor may be configured to cause detection of a level of liquid in the detection vessel. In conjunction with any of the above embodiments, the inversion of the excitation signal applied to the first capacitor may be configured to cause compensation for a change in capacitance in the second capacitor due to a change in the environment.

Embodiments of the present disclosure may include a system. The system may include any of the above-described level sensing controllers. The system may include an electrode assembly. The electrode assembly may include the sensing electrode and the pole electrode described above.

Embodiments of the present disclosure may include a method for determining a liquid level. The method may include the operation of any of the controllers and systems described above.

Fig. 1 is an illustration of an example system 100 for bipolar mutual capacitive liquid sensing, in accordance with an embodiment of the present disclosure. The system 100 may be used to sense the level of a liquid in any suitable application, such as in consumer devices, storage tanks, automotive applications, storage, water, wastewater, utilities, or oil and gas. The system 100 may be configured to determine the level/, of liquid in any suitable container 104. Although the container 104 is shown as a cylinder, any suitable shape, arrangement, or orientation of containers may be used. The level/of the liquid may be defined with reference to any suitable other portion of the container 104, such as the bottom of the container 104. System 100 may be configured to take measurements of/periodically, on demand, or according to any suitable stimulus or criteria. System 100 may be configured to report the measured value of/or to generate a warning that/reaches an upper or lower threshold periodically, on demand, or according to any suitable stimulus or criteria.

The system 100 may include a controller 102. The controller 102 is shown in more detail in fig. 3, discussed in more detail further below. The controller 102 may be implemented by digital circuitry, analog circuitry, instructions for execution by a processor, or any suitable combination thereof consistent with the teachings of the present disclosure. In one embodiment, the controller 102 may include interfaces for multiple bipolar mutual capacitive sensors or portions of the sensors. The controller 102 may include a signal generation circuit to be applied to a bipolar mutual capacitive sensor. Further, the controller 102 may include circuitry for integrating the signals received from the bipolar mutual capacitive sensor.

The system 100 may include an electrode assembly 104 coupled to a container 106. The electrode assembly 106 may be coupled to the container 104 either externally or internally of the container 104. The electrode assembly 106 is shown in more detail in fig. 2, which is discussed in more detail further below. The electrode assembly 106 may include any suitable number and type of electrodes. Such electrodes may be arranged in 1:1 or 1: N pairs with each other. Further, such electrodes may form capacitors when receiving an excitation signal. The excitation signal may be received from the controller 102. The excitation signal may be routed to the transmit and receive electrodes of the electrode assembly 106. When applied to a pair of electrodes, the excitation signal may facilitate 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 may be used as a proximity estimate to the liquid in the container 104. The position of the electrode relative to the container 104 may be known, and thus the associated capacitance measurement may be used to determine whether the liquid has reached a given level/in the container 104, where the position of the electrode at which the proximity detection or change is made may indicate that the liquid has reached the known position of the electrode.

The controller 102 may be configured to sequentially measure the capacitance at the electrode pairs of the electrode assemblies 106 in the vessel 104 and report the proximity of the liquid in any suitable manner. The controller 102 may, for example, start with a pair of electrodes at the top of the electrode assembly 106 and work towards a pair of electrodes 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. Controller 102 may report whether each such electrode pair has detected proximity of a liquid to the electrode pair. Controller 102 may report a given level l associated with the highest electrode pair that detected proximity to the liquid. In another embodiment, when the proximity of the liquid in the container 104 is determined while evaluating the electrode pairs from top to bottom, the controller 102 may report this detection and the level/of the electrode pair making this detection.

Fig. 2 is a more detailed illustration of the electrode assembly 106 for bipolar mutual capacitive liquid sensing, according to an embodiment of the present disclosure. Further, fig. 2 shows the charge applied to the various electrodes of the electrode assembly 106 over time in order to scan the capacitance values and thus the liquid proximity of the electrodes.

The electrode assembly 106 may include a sensing electrode 210. During polling of the electrodes in the electrode assembly 106, the sense electrodes 210 are available for connection to a collection node or sense node of the controller 102. Sensing electrode 210 may be a first electrode of a plurality of pairs of electrodes formed for proximity detection. The sensing electrode 210 may include a high input impedance. When connected to the sense electrode 210, the controller 102 may precharge the sense electrode 210 to half of the supply voltage. During subsequent measurements, the voltage of the sense electrode 210 may float.

Electrode assembly 106 can include two or more second electrodes or pole electrodes 212A-212H. Each of pole electrodes 212A-212G may be operable to connect to a positive signal from controller 102 during polling of a given pole electrode and to ground during polling of other ones of pole electrodes 212A-212G. Pole electrode 212H can be used to connect to a negative signal from controller 102 during polling of pole electrodes 212A-212G.

The pole electrodes 212A-212H may be configured to operate as transmitting electrodes of a capacitive sensor. The sensing electrode 210 may be configured to operate as a receiving electrode of a capacitive sensor. Thus, each pair of electrodes, including the sense electrode 210 and one of the pole electrodes 212A-212H, may be a capacitive sensor and may be represented as a capacitor.

In the example of fig. 2, the electrode assembly 106 may be vertically disposed along the side of the container 104. Thus, the pole electrodes 212A-212G may be vertically arranged from bottom to top within the electrode assembly 106. The pole electrode 212H may be disposed on top of the electrode assembly 106. Each of the pole electrodes 212A-212G may be configured to indicate whether the liquid in the vessel 104 has reached a vertical position associated with a given one of the pole electrodes 212A-212G. Based on the detection or proximity sensing provided by a given one of the electrodes 212A-212G and the known position or height of the electrodes 212A-212G, the system 100 is able to determine the level/of the liquid in the container 104.

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

To scan the electrode combination for proximity to the liquid in container 104, at (1), sensing electrode 210 can be connected to a collection node of controller 102, a negative signal or pulse can be applied to pole electrode 212H, a ground can be applied to pole electrodes 212B-212G, and a positive signal or pulse can be applied to pole electrode 212A. If the liquid in container 104 is at the level of pole electrode 212A, the capacitive sensor formed by the combination of pole electrode 212H, pole electrode 212A, and sensing electrode 210 can indicate to system 100 the proximity of the liquid to pole electrode 212A.

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

At (3) - (7), this same polling may be performed for the pole electrodes 212C-212G.

Although FIG. 2 is described as applying a negative signal to pole electrode 212H, a positive signal to a respective one of pole electrodes 212A-212G, and connecting sensing electrode 210 to a collection node of controller 102, any suitable signals and voltages may be applied so as to produce a capacitive sensor between pole electrode 212H and sensing electrode 210 and between sensing electrode 210 and a given one of pole electrodes 212A-212G. In one embodiment, a negative signal can be applied to a given few of pole electrodes 212A-212G, and a positive signal can be applied to pole electrode 212H. Any voltage value may be used for the negative and positive signals so long as a falling edge is applied to pole electrode 212 while a rising edge is applied to a respective one of pole electrodes 212A-212G, or so long as a rising edge is applied to pole electrode 212 while a falling edge is applied to a respective one of pole electrodes 212A-212G. The rising and falling edges may have substantially the same absolute magnitude and rate of change.

Fig. 3 is a more detailed illustration of the controller 102 for bipolar mutual capacitive liquid sensing, according to an embodiment of the present disclosure. Furthermore, fig. 3 shows a portion of the electrode array 106 where the capacitive sensor has been formed.

Controller 102 may include a terminal 306 for connection to pole electrode 212H of electrode assembly 106. Further, the controller 102 may include a terminal 320 for connection to the sensing electrode 210 of the electrode assembly 106. Further, the controller 102 may include terminals 308A-308G for connection to each of the pole electrodes 212A-212G.

The connections between controller 102, sense electrode 210, and pole electrodes 212A-212H may form capacitive sensors in electrode assembly 106, represented in FIG. 3 by capacitors 310, 312A-312G. The connections from terminal 306 to pole electrode 212H and from terminal 320 to sense electrode 210 can form capacitor 310.

The connections from terminal 308A to pole electrode 212A and from terminal 320 to sense electrode 210 may form capacitor 312A. The connections from terminal 308B to pole electrode 212B and from terminal 320 to sense electrode 210 may form capacitor 312B. Similarly, the connections from terminals 308C-308G to pole electrodes 212C-212G and from terminal 320 to sense electrode 210 can form capacitors 312C-312G (terminals 308C-308F, capacitors 312C-312F, and associated connections and branches are not shown).

The controller 102 may include a sense signal generator 302. The sensing signal generator 302 may be configured to generate a pulsed signal, an excitation signal, a transmission signal, or any other suitable signal for the transmitting electrode of the capacitive sensor. The sense signal generator 302 may be implemented by analog circuitry, digital circuitry, instructions for execution by a processor, or any suitable combination thereof. In the example of fig. 3, the sense signal generator 302 may be configured to generate a positive pulse signal when the controller 102 evaluates the capacitance of a given capacitive sensor.

The positive pulse signal generated by sense signal generator 302 may be routed to inverter 304 and the resulting negative pulse signal may be routed to terminal 306 for application to pole electrode 212H. The positive pulse signal generated by sense signal generator 302 may be further routed to switch 318, which in turn may route the positive pulse signal to a selected one of terminals 308A-308G for application to a selected one of pole electrodes 212A-212G.

The switch 318 may be implemented in any suitable manner, such as a multiplexer, a switch fabric, a switch matrix, or other suitable fabric. Switch 318 may be configured to send a positive pulse signal to a selected one of terminals 308A-308G and a ground signal to the other of terminals 308A-308G.

The controller 102 may include a control circuit 320. Control circuit 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, the control circuit 320 may be implemented by digital logic, an application specific integrated circuit, a field programmable gate array, a processor, or a microcontroller. The control circuit 320 may be configured to control the operation, timing, polling, and result collection of the sensors of the system 100. For example, the control circuit 320 may be configured to specify when the sensing signal generator 302 generates a pulse to perform a measurement in the electrode assembly 106. Further, control circuit 320 may be configured to specify which terminals of switch 318 will receive pulses and which terminals will receive ground signals. Accordingly, control circuitry 320 may specify which of electrodes 212A-212G are to perform proximity detection of liquid in container 104 at a given time. Further, the control circuitry 320 may be configured to collect measurement results, store the results in memory, or report the results to other entities 108.

The capacitance of the capacitor 310 and the capacitors 312A-312H may vary depending on whether a given one of such capacitors is in close proximity to the liquid in the container 104. In one embodiment, pole electrode 212H can be excluded from the range of liquids in container 104. Thus, the capacitance of the capacitor 310 may not be affected by the level/of the liquid in the container 104. Thus, the capacitance of the capacitor 310 may remain constant throughout the range of levels of liquid in the vessel 104. However, the capacitance of the capacitor 310 may vary depending on different environmental conditions, such as temperature, humidity, or electromagnetic interference, in which the system 100 is used. If a given one of pole electrodes 212A-212G is proximate to the liquid in container 104, the capacitance between the given pole electrode and sensing electrode 210, and thus the capacitance of the associated one of capacitors 312A-312G, will change. However, the capacitance of the capacitors 312A-312G may also vary depending on different environmental conditions in which the system 100 is used, such as temperature, humidity, or electromagnetic interference.

Controller 102 may be configured to determine whether the capacitance of one or more of capacitors 312A-312G has changed, thereby indicating the proximity of a respective one of pole electrodes 212A-212G to the liquid in container 104. The controller 102 may then poll or evaluate each or one or more of the capacitors 312A-312G. The controller 102 may be configured to evaluate the capacitance of a given one of the capacitors 312A-312G and compare the capacitance of the given one of the capacitors 312A-312G to the capacitance of the capacitor 310. The controller 102 may be configured to compare the capacitance of one of the capacitors 312A-312G to the capacitance of the capacitor 310 by, for example, evaluating the charge at a point between the given one of the capacitors 312A-312G and the capacitor 310.

When a given one of the capacitors 312A-312G is selected for evaluation by applying a positive signal to a respective one of the terminals 308A-308G, ground may be applied to the other of the terminals 308A-308G and a negative signal may be applied to the 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 capacitor 312A and capacitor 310, different amounts of charge will accumulate on the bottom plate of capacitor 310 and the top plate of capacitor 312A. If the capacitance of capacitor 312A and capacitor 310 are the same, a certain amount of charge will accumulate. A situation may occur in which the electrode 212A of the capacitor 312A is not adjacent to the liquid in the container 104.

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 cannot be distinguished from the liquid-induced capacitance change in the container 104 based on the rate of change, as the liquid-induced capacitance change in the container 104 may also be slow. In one embodiment, including capacitor 310 may account for this slow environmental change in capacitance of capacitor 312A, as the two capacitors, which are implemented in common electrode assembly 106, on the same printed circuit board, or by replication of material, may have the same expected capacitance. Capacitor 310 and capacitor 312A may experience the same environmental changes. Due to the applied signal from the sense signal generator 302, the capacitor 310 may have the same expected charge as the capacitor 312A, albeit with opposite polarity. Thus, the capacitor 310 may provide compensation for the change in capacitance experienced by the capacitor 312A due to environmental changes.

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

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

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

Fig. 4 is an illustration of a method 400 for bipolar mutual capacitive liquid sensing, in accordance with an embodiment of the present disclosure. The steps of method 400 may be performed by, for example, any suitable portion of the elements of fig. 1-3, 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 performed recursively. The steps of method 400 may be performed in the order discussed below, or in any other suitable alternative order. Further, more or fewer steps may be performed during the performance of the method 400 than those shown in fig. 4. Some portions of the method 400 may be performed by instructions for a processor stored in a non-transitory machine-readable medium. The instructions, when loaded and executed by a processor, may cause the processor to perform the steps of method 400.

At step 405, it may be determined whether a level of liquid in the container is found. Whether to find the level of liquid may be determined, for example, by a larger appliance or system, on demand, periodically, or according to any other suitable criteria. If a level of liquid is to be found, the method 400 may proceed to step 410. Otherwise, the method 400 may proceed to step 470.

At step 410, a positive sense pulse may be generated. At step 415, the positive sense pulse may be inverted to generate a negative sense pulse. At step 420, a negative sense pulse may be sent to a negative polarity electrode in an electrode assembly adjacent to or disposed within the container. Sending a negative sense pulse to the negative polarity electrode may charge a negative polarity capacitor to be formed by the negative polarity electrode and the sense electrode. The sensing electrodes may be connected to a controller or other collection node of a device performing method 400.

At step 425, a positive polarity electrode in an electrode assembly adjacent to or disposed within the container may be selected. In one embodiment, the positive polarity electrode may be selected as the highest electrode that has not been evaluated.

At step 430, a positive sense pulse may be sent to the selected positive polarity electrode. Sending a positive sense pulse to the selected positive polarity electrode may charge a positive polarity capacitor to be formed by the selective positive polarity electrode and the sense electrode.

At step 435, other positive polarity 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 measurements associated with the positive polarity electrode selected for evaluation.

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

At step 455, a report or other indicator may be generated for the selected positive polarity electrode or its position indicating that the liquid level of the container has reached the selected positive polarity electrode or its position. The method 400 may proceed to step 470.

At step 460, it may be determined whether there are additional positive polarity electrodes that have not yet been evaluated. If so, the method 400 may proceed to step 425 where a next electrode may be selected for evaluation. Otherwise, the method 400 may proceed to step 465.

At step 465, it may be determined that the container is empty. The method 400 may proceed to step 470.

At step 470, it may be determined whether the method 400 may be repeated. The 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 the method 400 is to be repeated, the method 400 may proceed to step 405, or if the method 400 is not to be repeated, the method may proceed to step 475 to terminate.

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