Continuous liquid level sensing system using projected capacitance

Abstract

The present invention provides a continuous liquid level sensing system using a projected capacitor, comprising: a liquid contact layer having at least one surface for contacting a liquid, the liquid contact layer separating the liquid to create a dry space; the projection type capacitor unit is arranged in the space and has a preset first capacitance value, the projection type capacitor unit is not in direct contact with the liquid, and the projection type capacitor unit is in contact with the liquid contact layer; when a preset electric field of the projection type capacitor unit is changed after the liquid contact layer is in contact with the liquid, the first capacitance value is changed into a second capacitance value; and the control device is used for calculating the liquid level height of the liquid according to the change between the first capacitance value and the second capacitance value.

Description

Technical Field

[0001] The present invention relates to a liquid level sensing system, and more particularly to a liquid level sensing system using projected capacitance and having continuous liquid level sensing. Background Art

[0002] Since the currently known technology is the resistive level meter, the resistance output of the resistive level meter changes with the liquid level, and the resistance output of the sensor is inversely proportional to the height of the liquid: the lower the liquid level, the higher the output resistance; the higher the liquid level, the lower the output resistance. The disadvantage is that the internal circuit of the resistive level meter needs to be in direct contact with the liquid, so it is easy to cause circuit damage. In addition, the current capacitance level meter capacitors are all ground capacitors, which belong to the self-capacitive circuit architecture, require reference capacitance or resistance design, and have no continuous scale measurement function, so the accuracy is easily limited. Summary of the invention

[0003] The invention discloses a projected capacitive continuous liquid level sensing system, which uses a projected capacitive circuit architecture.

[0004] The invention discloses a projected capacitive continuous liquid level sensing system, which uses a mutual capacitance circuit architecture.

[0005] The invention discloses a projected capacitive continuous liquid level sensing system, wherein the internal circuit does not need to directly contact the liquid.

[0006] The present invention discloses a continuous liquid level sensing system using projected capacitance, comprising: a liquid contact layer having at least one surface for contacting a liquid, and the liquid contact layer is used to separate the liquid to generate a dry space; and a projected capacitance unit, which is arranged in the space and has a preset first capacitance value, the projected capacitance unit does not directly contact the liquid, and the projected capacitance unit contacts the liquid contact layer; when the liquid contact layer changes a preset electric field of the projected capacitance unit after contacting the liquid, the first capacitance value changes to a second capacitance value; and a control device, which calculates a liquid level height of the liquid according to the change between the first capacitance value and the second capacitance value.

[0007] According to an embodiment of the present invention, the projected capacitive unit is not disposed in the area where the liquid is located, or the liquid contact layer is disposed and contacts the outer wall of the storage container.

[0008] According to an embodiment of the present invention, the projected capacitive unit is disposed in the area where the liquid is located, the liquid contact layer surrounds and covers the projected capacitive unit and blocks the contact between the liquid and the projected capacitive unit, and the liquid contact layer is disposed inside a storage container.

[0009] According to an embodiment of the present invention, the liquid contact layer is disposed on an inner wall of a storage container of the liquid, and the projected capacitive unit is disposed inside the storage container.

[0010] The continuous liquid level sensing system of the present invention utilizes a mutual capacitance projected capacitor circuit structure. Since the mutual capacitance projected capacitor does not need to be grounded in the liquid level measurement area, its architecture does not have reference capacitors and resistors. Therefore, it can be set at any position of the liquid for non-direct contact sensing, further avoiding damage caused by direct contact of the circuit with the liquid. In addition, the more projected capacitor units there are, the higher the measurement accuracy. The present invention has an architecture with additional series projected capacitor units to increase the flexibility and sensitivity of measuring the liquid level. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1A to Figure 1F A schematic diagram showing an embodiment of the present invention.

[0012] Figure 2A to Figure 2B A schematic diagram showing an embodiment of a projected capacitive unit of the present invention.

[0013] Figure 3 A liquid level calculation method according to an embodiment of the present invention is shown.

[0014] Figure 4 A schematic diagram showing an embodiment of the present invention.

[0015] Figure 5 A schematic diagram showing the invention's ability to serially expand measurement length.

[0016] Figure 6 Schematic diagram showing the calculation of a tilted container.

[0017] Reference numerals:

[0018] 100A, 100B, 100C, 400: Continuous Liquid Level Sensing System

[0019] 101: Liquid contact layer

[0020] 102: Projected capacitive unit

[0021] 103: Control device

[0022] 104:AFE device

[0023] 105:CPU

[0024] 106: Liquid level sensing computing unit

[0025] 107: memory unit

[0026] 108: User Interface

[0027] 109: Non-volatile storage unit

[0028] 110: Host side

[0029] S1: Surface

[0030] S2: Space

[0031] L:Liquid

[0032] B: Storage container

[0033] Tx: Array Y-axis drive sensor

[0034] Rx: Array type X-axis receiving induction line

[0035] 102Y:Y-axis electrode

[0036] 102X: X-axis electrode DETAILED DESCRIPTION

[0037] Please also refer to Figure 1A and Figure 1B , Figure 1A A schematic diagram showing an embodiment of the present invention is shown. Figure 1B show Figure 1A The present invention discloses a continuous liquid level sensing system 100A using projected capacitance, comprising: a liquid contact layer 101, a projected capacitance unit 102, a control device 103, and an AFE (analog front end) device 104; wherein a storage container B stores liquid L.

[0038] In one embodiment, the liquid contact layer 101 is a waterproof insulator with a low dielectric constant, such as glass, a printed circuit board PCB (Printed circuit board), acrylic, or polycarbonate (PC).

[0039] The liquid contact layer 101 has a surface S1 for contacting the liquid L, and the liquid contact layer 101 is used to separate the liquid L to generate a dry space S2. The projected capacitive unit 102 is disposed in the space S2. In other words, the liquid contact layer 101 separates the present invention into a space with liquid L and a space without liquid L, or allows the projected capacitive unit 102 to not directly contact the liquid L. The projected capacitive unit 102 contacts the liquid contact layer 101.

[0040] The projected capacitive unit 102 has a preset first capacitance value; when the liquid contact layer 101 contacts the liquid L and changes the preset electric field of the projected capacitive unit 102, the first capacitance value of the projected capacitive unit 102 becomes a second capacitance value. In this way, the control device 103 calculates the liquid level of the liquid L based on the change between the first capacitance value and the second capacitance value.

[0041] Please note that in the continuous liquid level sensing system 100A, the projected capacitive unit is disposed in the area where the liquid L is located, and the liquid contact layer 101 surrounds and covers the projected capacitive unit 102, so the liquid contact layer 101 isolates the contact between the liquid L and the projected capacitive unit 102; in other words, the projected capacitive unit 102 is covered by the liquid contact layer 101, and the liquid contact layer 101 prevents the projected capacitive unit 102 from directly contacting the liquid L. When the liquid L contacts the liquid contact layer 101 as a conductor, the capacitance value of the projected capacitive unit 102 will change, and the control device 103 calculates the liquid level of the liquid L according to the change in capacitance value.

[0042] Please refer to Figure 1C and Figure 1D , Figure 1C A schematic diagram showing an embodiment of the present invention is shown. Figure 1D show Figure 1C The difference between the continuous liquid level sensing system 100B using projected capacitance and 100A of the present invention is that the liquid contact layer 101 in the continuous liquid level sensing system 100B is disposed and contacts the inner wall of the storage container B, and the projected capacitance unit 102 is disposed inside the storage container B.

[0043] Please refer to Figure 1E and Figure 1F , Figure 1E A schematic diagram showing an embodiment of the present invention is shown. Figure 1F show Figure 1E The difference between the continuous liquid level sensing system 100C using projected capacitance and 100A of the embodiment of the present invention is that the projected capacitance unit 102 is not disposed in the area where the liquid L is located, and the liquid contact layer 101 can be a part of the storage container B of the liquid L, or the liquid contact layer 101 is disposed and contacts the outer wall of the storage container B.

[0044] Please note that the liquid contact layer 101 can serve as a protective structure for the projected capacitive unit 102 to prevent the projected capacitive unit 102 from malfunctioning. In addition, the projected capacitive unit 102 needs to contact the liquid contact layer 101 , but the projected capacitive unit 102 does not contact the liquid L directly.

[0045] Please refer to Figure 2A , Figure 2A A schematic diagram showing an embodiment of a projected capacitive unit of the present invention. The projected capacitive unit 102 includes an array of Y-axis driving sensing lines Tx(1) and an array of X-axis receiving sensing lines Rx(1) to Rx(2). Please note that Figure 2A For the sake of simplicity, only some array units are drawn as schematic diagrams.

[0046] The array-type Y-axis driving sensing line Tx(1) is coupled to the Y-axis electrode 102Y, and the array-type X-axis receiving sensing lines Rx(1)-Rx(2) are coupled to the plurality of X-axis electrodes 102X. This figure only shows two Y-axis electrodes 102Y(1)-102Y(2) and two X-axis electrodes 102X(1)-102X(2), but the present invention should not be limited thereto. The Y-axis electrodes 102Y(1)-102Y(2) and the X-axis electrodes 102X(1)-102X(2) are connected to the Y-axis electrodes 102Y(1)-102Y(2). The electrodes are arranged in a staggered manner, and the connecting lines between adjacent Y-axis electrodes 102Y(1) to 102Y(2) cross and do not touch the connecting lines between adjacent X-axis electrodes 102X(1) to 102X(2), that is, the connecting lines between adjacent X-axis electrodes 102X(1) to 102X(2) cross the connecting lines between adjacent Y-axis electrodes 102Y(1) to 102Y(2), and there is a first mutual capacitance value CM between the Y-axis electrode 102Y and the X-axis electrode 102X.

[0047] Please note that in this embodiment, the driving sensing line Tx is coupled to the Y-axis electrode 102Y, and the receiving sensing line Rx is coupled to the X-axis electrode 102X, but the present invention should not be limited thereto, and the driving sensing line Tx may be coupled to the X-axis electrode 102X, and the receiving sensing line Rx may be coupled to the Y-axis electrode 102Y.

[0048] In one embodiment, each of the projected capacitive units 102 includes an X-axis electrode 102X and a Y-axis electrode 102Y.

[0049] As mentioned above, each Y-axis electrode 102Y and each X-axis electrode 102X is in a square shape.

[0050] Please refer to Figure 2B , Figure 2B A schematic diagram showing an embodiment of a projected capacitive unit of the present invention is shown, wherein an AFE device 104 is coupled to a plurality of array-type Y-axis driving sensing lines Tx(1)-Tx(n) and a plurality of array-type X-axis receiving sensing lines Rx(1)-Rx(n), and a control device 103 sequentially transmits a driving signal to the array-type Y-axis driving sensing lines Tx(1)-Tx(n), and continuously receives sensing signals from the array-type X-axis receiving sensing lines Rx(1)-Rx(n) to continuously scan the liquid level. The control device 103 adjusts the driving signal so that the driving signal varies according to time and has a non-fixed waveform, and the driving signal has a maximum signal-to-noise ratio within a unit time.

[0051] The control device 103 transmits a driving signal to the array of Y-axis driving sensing lines Tx(1)~Tx(n) for charging. The array of X-axis receiving sensing lines Rx(1)~Rx(n) senses the array of Y-axis driving sensing lines Tx(1)~Tx(n) to generate a sensing signal. At this time, a first capacitance value CM exists between the Y-axis electrode 102Y and the X-axis electrode 102X. When the liquid contact layer 101 contacts the projected capacitive unit 102, the charge is discharged. At this time, the first capacitance value CM between the array of Y-axis driving sensing lines Tx and the array of X-axis receiving sensing lines Rx has changed to a second capacitance value, and the sensing signal also changes accordingly. The control device 103 calculates the liquid level according to the change of the sensing signal.

[0052] In more detail, the control device 103 transmits a driving signal to the array Y-axis driving sensing lines Tx(1)~Tx(n) for charging, and the array X-axis receiving sensing lines Rx(1)~Rx(n) sense the array Y-axis driving sensing lines Tx(1)~Tx(n) to generate a sensing signal. At this time, the Y-axis electrode 102Y and the X-axis electrode 102X have a first capacitance value CM. When the liquid contact layer 101 contacts the projected capacitive unit with the liquid, the charge is discharged. At this time, the first capacitance value CM of the Y-axis electrode 102Y and the X-axis electrode 102X is reduced and changed. In other words, at this time, the capacitance between the Y-axis electrode 102Y and the X-axis electrode 102X has changed to a second capacitance value (not shown). Due to the difference between the first capacitance value CM and the second capacitance value, the control device 103 calculates the liquid level according to the change of the sensing signal.

[0053] Since the operating principle of the projected capacitive unit 102 is to form an X-axis and a Y-axis electric field under the liquid contact layer 101, the electric field lines pass through the surface of the liquid contact layer 101 to maintain the electric field balance; once the liquid approaches the liquid contact layer 101, the liquid and the X-axis electrode 102X or the Y-axis electrode 102Y form a new electric field, so that the local electrostatic capacitance changes simultaneously between multiple electrodes. The control device 103 can accurately determine the position and liquid level by measuring the ratio between these charges.

[0054] Please refer to Figure 3 , Figure 3 The liquid level calculation method of one embodiment of the present invention is shown. The present invention can use a general hardware scale (1mm) as a visual reference for the liquid level height (as shown on the left side of the figure), but we can perform digital operations based on the voltage or current change ratio of the projected capacitive unit 102 to achieve stepless continuous measurement between two adjacent electrodes (as shown on the right side of the figure). The operation of one embodiment can be interpolated to obtain a liquid level height (for example: 0.1mm) that is more accurate than the actual hardware scale (1mm).

[0055] For example, if the liquid level is at about 4 cm on the scale, the capacitance of the X-axis electrode 102X or the Y-axis electrode 102Y near the liquid level (such as the dotted box) changes, causing the ratio between the current (voltage) of the X-axis electrode 102X or the Y-axis electrode 102Y to change, and then the analog front end (AFE) device 104 (not shown) obtains the corresponding digital signal, and then the liquid level sensing calculation unit (not shown) in the control device 103 interpolates and calculates a more accurate liquid level height of 4.08 cm. (Scale according to the figure)

[0056] Please refer to Figure 4 , Figure 4 As mentioned above, the continuous liquid level sensing system 400 using projected capacitance further includes an AFE device 104, and the control device 103 further includes a central processing unit (CPU) 105, a liquid level sensing calculation unit 106, a memory unit 107, a user interface 108, and a non-volatile storage unit 109.

[0057] The AFE device 104 is coupled between the control device 103 and the projected capacitive unit 102. The AFE device 104 charges the array Y-axis driving sensing line Tx according to the control device 103, and converts the sensing signal of the array X-axis receiving sensing line Rx into a digital signal and outputs it to the control device 103; wherein the voltage or current change generated by the difference between the first capacitance value and the second capacitance value is converted into a digital signal by the AFE device 104.

[0058] The CPU 105 is used to generate a driving signal to measure the liquid level. The liquid level sensing unit 106 calculates the liquid level according to the digital signal from the AFE device 104 and outputs it to the memory unit 107 for storage. The user interface 108 is used to control the CPU 105 to generate the driving signal to measure the liquid level and monitor the liquid level.

[0059] Please note that the non-volatile storage unit 109 stores an initial reference value in advance. When the continuous liquid level sensing system 100 is initially powered on, it will first read the reference value in the non-volatile storage unit 109. The AFE device 104 calibrates the projected capacitive unit 102 according to the reference value. Then the CPU 105 controls the liquid level sensing operation unit 106 to calculate the liquid level height according to the digital signal from the AFE device 104.

[0060] In one embodiment, the projected capacitive unit 102 is placed in liquids with three different standard liquid level heights (low / medium / high), for example: 10 cm liquid level, 30 cm liquid level, and 50 cm liquid level, and then the liquid level sensing operation unit 106 calculates the offset of the projected capacitive unit 102 according to the digital signal of the AFE device 104 as a reference value and stores it in the non-volatile storage unit 109.

[0061] Please refer to Figure 5 , Figure 5 A schematic diagram showing the invention can be connected in series to expand the measured length. When the liquid level is higher, the two projected capacitive units 102 are connected in series through an integrated bus circuit (I2C BUS), a serial peripheral interface (SPI), or a universal serial bus (USB), and the user interface 108 communicates with the host terminal 110 to calculate the total height.

[0062] The calibration of this embodiment is the same as described above. Before the series connection, the projected capacitive units 102 are placed in liquids with three different standard liquid level heights (low / middle / high), for example, 10 cm liquid level, 30 cm liquid level, and 50 cm liquid level. Then, the liquid level sensing calculation unit 106 calculates the offset of each projected capacitive unit 102 as a reference value according to the digital signal of the AFE device 104. The reference value is stored in the non-volatile storage unit 109 for use in the initial calibration at startup. After the series connection, the user places the two projected capacitive units 102 in series into liquids with three different standard liquid level heights (low / middle / high), for example, 10 cm liquid level, 30 cm liquid level, and 50 cm liquid level, and then compares the calculated liquid level values ​​of the two projected capacitive units 102 in series to see if they are within the average error specification value (for example, 0.1%).

[0063] Please refer to Figure 6 , Figure 6A schematic diagram showing (multi-driving / multi-sensing) calculating a tilted container. In this embodiment, the projected capacitive unit 102 covers the entire inner wall of the container, or the projected capacitive unit 102 covers the entire outer wall of the container, or a plurality of projected capacitive units 102 are disposed in the container. When the container is not tilted, the projected capacitive units on both sides have the same liquid level; when the container is tilted due to some factors, the CPU generates a driving signal to measure the liquid level, and the tilt of the liquid surface can be detected by transmitting the driving signal to the projected capacitive units on both sides, and then the liquid level sensing computing unit calculates the tilt angle and estimates the actual accurate liquid level.

[0064] In summary, the continuous liquid level sensing system of the present invention utilizes the circuit structure of mutual capacitance projected capacitance, and because mutual capacitance projected capacitance does not need to be grounded in the liquid level measurement area, its architecture does not have reference capacitors and resistors, so it can be set at any position of the liquid for non-direct contact sensing, further avoiding damage caused by direct contact between the circuit and the liquid; in addition, the more projected capacitance units there are, the higher the measurement accuracy can be. The present invention has an architecture with additional projected capacitance units connected in series, which increases the flexibility and sensitivity of measuring the liquid level.

Claims

1. A continuous liquid level sensing system using projected capacitance, characterized in that: Include: a liquid contact layer having at least one surface for contacting a liquid, and the liquid contact layer is used to separate the liquid to create a dry space; and a projected capacitive unit disposed in the space and having a preset first capacitance value, the projected capacitive unit not directly contacting the liquid, and the projected capacitive unit contacting the liquid contact layer; when the liquid contact layer contacts the liquid and changes a preset electric field of the projected capacitive unit, the first capacitance value changes to a second capacitance value; as well as A control device calculates a liquid level of the liquid according to the change between the first capacitance value and the second capacitance value.

2. The system according to claim 1, characterized in that The projected capacitive unit is not disposed in the area where the liquid is located, and the liquid contact layer can be a part of a storage container of the liquid, or the liquid contact layer is disposed and contacts the outer wall of the storage container.

3. The system according to claim 1, characterized in that The projected capacitive unit is arranged in the area where the liquid is located, the liquid contact layer surrounds and covers the projected capacitive unit and blocks the contact between the liquid and the projected capacitive unit, and the liquid contact layer is arranged inside a storage container of the liquid.

4. The system according to claim 2, characterized in that The liquid contact layer is arranged on the inner wall of the storage container of the liquid, and the projected capacitive unit is arranged inside the storage container.

5. The system according to claim 1, wherein: The projected capacitive unit comprises: An array of Y-axis driving sensing lines coupled to a plurality of Y-axis electrodes; and An array type X-axis receiving sensing line coupled to a plurality of X-axis electrodes; The Y-axis electrodes and the X-axis electrodes are arranged in a staggered manner, and the connecting lines between adjacent Y-axis electrodes cross and do not touch the connecting lines between adjacent X-axis electrodes, and there is a first mutual capacitance value between the Y-axis electrodes and the X-axis electrodes.

6. The system according to claim 5, characterized in that The connection lines between adjacent X-axis electrodes cross over the connection lines between adjacent Y-axis electrodes.

7. The system according to claim 6, characterized in that The control device is coupled to the array-type Y-axis driving sensing line and the array-type X-axis receiving sensing line. The control device sequentially transmits a driving signal to the array-type Y-axis driving sensing line and continuously receives a sensing signal from the array-type X-axis receiving sensing line to continuously scan the liquid level of the liquid. The control device adjusts the driving signal so that the driving signal changes according to time and has a non-fixed waveform, and the driving signal has a maximum signal-to-noise ratio within a unit time.

8. The system according to claim 7, characterized in that The control device transmits the driving signal to the arrayed Y-axis driving sensing line for charging, and the arrayed X-axis receiving sensing line senses the arrayed Y-axis driving sensing line to generate the sensing signal, and at this time, the first capacitance value exists between the Y-axis electrode and the X-axis electrode; when the liquid contact layer and the liquid contact the projected capacitive unit, the charge is discharged, and at this time, the second capacitance value exists between the Y-axis electrode and the X-axis electrode, and the control device calculates the liquid level of the liquid according to the change of the sensing signal.

9. The system according to claim 8, characterized in that The continuous liquid level sensing system includes: An analog front-end AFE device charges the array Y-axis driving sensing line according to the control device, and converts the sensing signal of the array X-axis receiving sensing line into a digital signal and outputs it to the control device; The voltage variation generated by the difference between the first capacitance value and the second capacitance value is converted into the digital signal by the AFE device.

10. The system according to claim 9, characterized in that The control device comprises: A central processing unit (CPU) for generating the driving signal to measure the liquid level; a liquid level sensing computing unit, which calculates the liquid level according to the digital signal and outputs it to a memory unit for storage; A user interface, used to control the CPU to generate the driving signal to measure the liquid level, or monitor the liquid level; A non-volatile storage unit, pre-stored with an initial reference value; The AFE device calibrates the projected capacitive unit according to the reference value, and then the CPU controls the liquid level sensing operation unit to perform operation, so that the liquid level sensing operation unit calculates the liquid level height according to the digital signal from the AFE device.

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