CN106352948B - Liquid level detection system and detection method of capacitive sensor - Google Patents
Liquid level detection system and detection method of capacitive sensor Download PDFInfo
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- CN106352948B CN106352948B CN201611037543.6A CN201611037543A CN106352948B CN 106352948 B CN106352948 B CN 106352948B CN 201611037543 A CN201611037543 A CN 201611037543A CN 106352948 B CN106352948 B CN 106352948B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/26—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields
- G01F23/263—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors
Abstract
A novel liquid level detection system and a detection method of a capacitive sensor are disclosed, and the system comprises: the device comprises a capacitance detection unit, a control chip unit, an output display unit and a power supply unit. The method comprises the following steps: 1), firstly setting initialization data by a control chip unit, 2), judging whether a liquid-free reference value A,3 is stored in a memory by the control chip unit, calling the liquid-free reference value A,4 in the memory by the control chip unit, detecting capacitance data of each detection end of a detection unit for N times (N is more than 1) by the control chip unit, and taking the average value of the capacitance data to obtain a liquid-containing reference value B; 5) Comparing the sizes of A and B; the device has the advantages of simple structure, low cost, corrosion and pollution prevention and high measurement precision.
Description
Technical Field
The present disclosure relates to liquid level detection systems and methods, and particularly to a liquid level detection system and method for a capacitive sensor.
Background
Fixed-point liquid level detection is to measure liquid levels at several fixed positions, such as upper limit indication, lower limit indication, segmented liquid level indication and the like. There are many liquid level measuring methods, including a capacitance method, a resistance method, a magnetostriction method, a magnetic flip plate method, a vibration method, a float level meter method, a laser level method, an optical fiber level method, a pressure difference method, and the like, a liquid level switching method, a safety valve method, a servo level meter method, and the like.
The differential pressure method is one of the most commonly used methods for measuring the liquid level in the storage tank at present, the method can ensure the accuracy of measurement only under the condition that the density of the liquid is constant, the density of the liquid is a multivariate function of the components and the temperature of the liquid under the actual condition, and the density is changed when the components and the temperature of the liquid are changed.
Ultrasonic liquid level measurement methods are various, and pulse echo methods are widely applied. The propagation speed of the ultrasonic wave is influenced by the density, pressure, temperature, concentration and other factors of the medium. The ultrasonic method liquid level measurement has simple structure and convenient installation and maintenance, belongs to non-contact measurement, can be used for liquid level measurement of toxic and corrosive gas and high-viscosity liquid, but is not suitable for liquid containing bubbles or solid particles.
The optical fiber liquid level measurement has high sensitivity, high response speed, electromagnetic interference resistance and corrosion resistance, is particularly suitable for flammable and explosive severe environments, and is suitable for liquid level measurement of various liquids. The disadvantage is that it is not possible to detect the level of dirty liquid and of viscous material that may adhere to the surface of the head.
The laser pulse method liquid level measurement applies a detection signal to laser with safe power, is suitable for flammable and explosive environments such as oil tank liquid level measurement and the like, has good safety, does not have movable parts, is convenient to maintain, and has strong anti-interference performance and relatively low price. Unfortunately, optical lenses are susceptible to contamination, affecting the measurement results.
The liquid level measured by the radar wave method can be used for measuring the liquid level of corrosive, high-viscosity and toxic liquid and the solid material level, a measuring device has no movable part and no measuring blind area, the propagation speed of the radar wave depends on the relative dielectric constant and the magnetic conductivity of a medium, so that the radar wave is not influenced by temperature, pressure and the like, and the radar wave belongs to non-contact measurement and has good real-time property. The disadvantages and the high price.
Disclosure of Invention
The invention aims to design a non-contact capacitive sensor liquid level detection system and a non-contact capacitive sensor liquid level detection method which are simple in structure, low in cost, resistant to corrosion and pollution and high in measurement accuracy, aiming at the defects of the prior art.
The object of the invention can be realized by the following technical scheme, and the liquid level detection system of the capacitive sensor comprises:
a capacitance detection unit: the liquid level detection end is used for detecting real-time capacitance data of the liquid level detection point;
a control chip unit: the system is used for detecting and comparing environmental capacitance data and real-time capacitance data of a liquid level detection end of the capacitance detection unit for multiple times and feeding back self-adaptive data of environmental change in real time, so as to obtain the state of the current calibrated liquid level and judge whether the liquid reaches the calibrated liquid level height;
an output display unit: the liquid level control chip unit is used for receiving signals of the control chip unit and giving corresponding liquid level state signals;
a power supply unit: for providing power to the system;
the capacitance detection unit is connected with a detection signal input end of the control chip unit, and the output display unit is connected with a signal output end of the control chip unit.
In the liquid level detection system of the capacitive sensor, a sensitivity adjustment capacitor for detecting sensitivity adjustment is arranged in a capacitance detection unit of the liquid level detection system.
The system of the liquid level detection system of the capacitive sensor further comprises a storage unit used for storing detection data of the detection unit and data of the control chip unit.
In the liquid level detection system of the capacitive sensor, the liquid level detection end of the capacitive detection unit is formed by connecting a detection electrode T and a resistor R in series, and the other end of the resistor R is connected with the detection signal input end of the control chip unit.
In the liquid level detection system of the capacitive sensor, the control chip unit is a controller or a singlechip with a capacitance detection function.
The output display unit of the capacitance type sensor liquid level detection system can be a display screen, a printing device, a light or sound display device.
A capacitive sensor liquid level detection method, the method comprising:
1) Firstly, the chip unit is controlled to set initialization data, including the following settings:
the capacitance data of each liquid level detection end of the capacitance detection unit in the absence of liquid is a no-liquid reference value A,
the chip unit is controlled to judge that the fixed difference value when the liquid level reaches the standard is delta Tup,
the fixed difference value when the control chip unit judges that the liquid level does not reach the standard is delta Tdn,
the control chip unit judges whether the liquid level is adaptive to the self-adaptive fixed difference value of the environmental change is delta Tadp;
2) The control chip unit judges whether a no-liquid reference value A is stored in the memory or not, if the data of the no-liquid reference value A is judged to be stored, whether the no-liquid reference value A is within a fixed difference value delta Tadp of environmental change or not is judged, and the next step is continued if the no-liquid reference value A is within the fixed difference value delta Tadp; if the capacitance data of the detection ends of the chip unit detection unit is not within the liquid-free state, the chip unit is controlled to detect the capacitance data of the detection ends of the detection unit under the liquid-free state, the capacitance data are read one by one and stored in a memory, and the data are set as a liquid-free reference value A;
3) The control chip unit calls a liquid-free reference value A in the memory;
4) Controlling the chip unit to detect capacitance data of each detection end of the detection unit for N times (N is more than 1), and taking the average value to obtain a liquid reference value B;
5) Comparing the sizes of A and B;
(1) If A > B: the control chip unit judges whether the liquid level is in a standard state, if so, the step 25 is returned; if the liquid level is not in the standard reaching state, A-B > delta Tup, the system confirms that the liquid level meets the standard reaching state, outputs a corresponding liquid level state signal and returns to the step 25; if A-B is less than delta Tadp, the system replaces the liquid-free reference value A with (A + B)/2, stores and returns to the step 25; if A-B < DeltaTadp is not established, the system judges whether the continuous occurrence frequency of the counting state exceeds 50 times (the detection frequency can be increased or decreased according to the actual application requirement), the exceeded system replaces the no-liquid reference value A with (A + B)/2, and stores the no-liquid reference value A and returns to the step 25; return to step 25 if not exceeded;
(2) If a = B: returning to step 25;
(3) And if A < B: the control chip unit judges whether the liquid level is in a standard-reaching state, if the liquid level is not in the standard-reaching state, the liquid-free reference value A is replaced by (A + B)/2, and the step 25 is stored and returned; if the liquid level is in the standard reaching state, judging B-A > deltase:Sub>A Tdn, if the liquid level is in the standard reaching state, confirming that the liquid level does not meet the standard reaching state, outputting ase:Sub>A corresponding liquid level state signal, returning to the step (4), and if the liquid level is not in the standard reaching state, returning to the step 25.
When the capacitive sensor liquid level detection method is used for judging whether A is greater than B, if the A-B is judged to be greater than a self-adaptive fixed difference value delta Tadp for 50 times continuously and is also judged to be less than a fixed difference value delta Tup for judging the liquid level to reach the standard, the system can be regarded as that the possibility is high due to the fact that the external environment (environmental factors such as temperature and humidity) changes, and the stored count value is slowly approximated to a real environment value (namely, the value of (A + B)/2 is adopted to replace A). Description of the drawings: a here is the original value A of the beginning; here, B is the current capacitance value of the real-time sampling reading.
The invention relates to a technology, which belongs to non-contact measurement, and the detection is to acquire the liquid level state through the condition of capacitance change. The capacitance change is not influenced by the density, chemical characteristics and the like of the liquid, and the liquid level detection technology is safe, low in cost and high in practicability. The liquid level meter can be widely used for measuring the liquid level of any liquid level with electrolyte, and can be used in industry, agriculture and daily life; no toxicity, no pollution, safety and convenience.
Description of the drawings:
FIG. 1 is a schematic block diagram of the structural principles of the present invention;
FIG. 2 is a schematic circuit diagram of the present invention;
fig. 3 is a block diagram of the process of the present invention.
The specific embodiment is as follows:
fig. 1 and fig. 2 are schematic block diagrams illustrating the structural principle of the present invention; the device comprises a capacitance detection unit 10, a control chip unit 11, an output display unit 12, a data storage unit 13 and a power supply unit 14. The data storage unit is adjusted correspondingly according to the characteristics of different controllers, namely, if some controllers contain EEPROM units, additional EEPROM is not needed to be hung externally, and if the selected controllers do not contain EEPROM units, separate EEPROM chips are needed to be hung externally.
The capacitance detection unit 10 is provided with a plurality of liquid level detection ends T1, T2, T3- - -Tn for performing real-time capacitance data detection on liquid level detection points, and the number of the detection ends is determined according to the liquid level detection points. The liquid level detection terminals T1, T2, T3-Tn are respectively connected with the detection signal input terminals SENS1, SENS2, and SEN of the control chip unit 11 through resistors R1, R2, R3-Rn,
SENS3- -SENSn. The detecting electrode T is formed by a part which can generate capacitance change along with the liquid level change, and the part can be a copper foil on a PCB (printed circuit board), an external metal conductor or any other conductive material which can generate capacitance change along with the liquid level change. The basic principle is as follows: when no liquid exists, the reading value of the capacitor is relatively stable and large, and when liquid reaches the corresponding height of the detection electrode, the reading value of the capacitor of the electrode is reduced, so that whether the liquid level reaches the standard can be judged only by monitoring the change of the reading value of the capacitor of the electrode, and the purpose of liquid level state indication or liquid level quantitative indication is achieved.
In order to accurately judge the fixed difference value when the liquid level reaches the standard, the adaptive fixed difference value delta Tup when the liquid level reaches the standard can be set by adjusting the capacitor C2 when the system is initialized.
In fig. 2, C1 is a filter capacitor, and in this embodiment, the control chip unit 11 is an ADATW08IC chip. The device is used for detecting and comparing environmental capacitance data and real-time capacitance data of a liquid level detection end of the capacitance detection unit 10 for multiple times and feeding back self-adaptive data of environmental changes in real time, so that the state of the current fixed-point liquid level is obtained, and whether the liquid reaches the liquid level height of the fixed point or not is judged.
The input end of the output display unit 12 is connected to the signal output ends IO1, IO2, IO3, and-IOn of the control chip unit 11, respectively, and the signal output end of the control chip unit 11 continuously outputs the data result of the liquid level, which can be output in various required data forms. Such as an IIC mode, a serial mode, a TTL level mode, etc.
The output display unit 12 may be one or more of a display screen, a printing device, a lighting device or a sound display device.
Fig. 3 is a block diagram of the present invention. In the figure, step 20 starts, power is supplied, the whole system is ready to start, step 21 initializes the system of the controller, and meanwhile, the liquid-free reference value A is found or the acquisition of the liquid-free reference value A is ready. Step 22 is to judge whether the environment correction action is needed currently, if yes, step 23 is to perform the environment correction, and then the formal liquid level detection link of step 25 is entered. If no correction of the environmental value is required, the step 24 is entered to directly obtain the liquid-free reference value A, and the data A is very important. Step 26 compares data a and data B and initiates adaptive compensation operations on the reference data to ensure that the environmental data is in a relatively accurate mathematical relationship with the liquid level data.
When A > B and A < B are compared, whether the liquid level is in a standard state or not is checked, a liquid level standard state flag bit is usually set in software to indicate the state of the liquid level, when the liquid level standard judgment condition is met, the liquid level standard state flag bit is set to be 1, and if not, the liquid level standard state flag bit is clear to be 0. The checking of the liquid level reaching state is realized by inquiring the liquid level reaching state flag bit.
When a < B is compared, (a + B)/2 is substituted for a as the stored value, the return to 25 is adaptive to the environment, and the stored count value approaches the true reading at a relatively slow rate, which mainly serves to distinguish to some extent a slow increase in liquid level from a slow change in environment.
Δ Tup is a fixed difference value when the liquid level is judged to be up to standard, the difference value is set by initialization, and the software can be set and adapted by adjusting the capacitor C2.
And delta Tdn is a fixed difference value when the liquid level is judged not to reach the standard, the difference value is set during initialization, and the software can be set and adapted by adjusting the capacitor C2.
Δ Tadp is a fixed difference that determines whether to adapt to environmental changes, which is set at initialization and can be adapted to software settings by adjusting capacitor C2.
In the program, if the continuous occurrence frequency of the counting state exceeds 50 times (the detection frequency can be increased or decreased according to the actual application requirement), if the (A-B) is judged to be greater than the self-adaptive fixed difference value and less than the fixed difference value for judging the liquid level to reach the standard for 50 times continuously, the possibility that the external environment (environmental factors such as temperature, humidity and the like) changes to cause larger possibility is considered, and the stored counting value is slowly approached to the real environment value.
Claims (5)
1. A capacitive sensor liquid level detection method based on a capacitive sensor liquid level detection system is characterized in that the detection system comprises:
a capacitance detection unit: at least one liquid level detection end for detecting real-time capacitance data of the liquid level detection point;
controlling the chip unit: the system is used for detecting and comparing environmental capacitance data and real-time capacitance data of a liquid level detection end of the capacitance detection unit for multiple times and feeding back self-adaptive data of environmental change in real time, so that the state of the current fixed-point liquid level is obtained, and whether the liquid reaches the liquid level height of the fixed point is judged;
an output display unit: the liquid level control chip unit is used for receiving signals of the control chip unit and giving corresponding liquid level state signals;
a power supply unit: for providing power to the system;
a storage unit: the data storage unit is used for storing detection data of the capacitance detection unit and data of the control chip unit;
the capacitance detection unit is connected with a detection signal input end of the control chip unit, and the output display unit is connected with a signal output end of the control chip unit;
the detection method comprises the following steps:
1) Firstly, controlling the chip unit to set initialization data, including setting:
the capacitance data of each liquid level detection end of the capacitance detection unit in the absence of liquid is a no-liquid reference value A,
the chip unit is controlled to judge that the fixed difference value when the liquid level reaches the standard is delta Tup,
the fixed difference value when the control chip unit judges that the liquid level does not reach the standard is delta Tdn,
the control chip unit judges whether the liquid level is to adapt to the self-adaptive fixed difference value of environmental change as delta Tadp;
2) The control chip unit judges whether a liquid-free reference value A is stored in the storage unit or not, if the data of the liquid-free reference value A is judged to be stored, whether the liquid-free reference value A is within a self-adaptive fixed difference value delta Tadp of the environmental change or not is judged, and the next step is continued if the liquid-free reference value A is within the self-adaptive fixed difference value delta Tadp of the environmental change; if the capacitance data is not within the range, the chip unit is controlled to detect the capacitance data of each liquid level detection end of the capacitance detection unit under the liquid-free state, the capacitance data is read one by one and stored in the storage unit, and the data is set as a liquid-free reference value A;
3) The control chip unit calls a liquid-free reference value A in the storage unit;
4) The control chip unit detects capacitance data of each liquid level detection end of the capacitance detection unit for N times, wherein N is greater than 1, and the average value is taken to obtain a liquid reference value B;
5) Comparing the sizes of A and B;
(1) If A > B: the control chip unit judges whether the liquid level is in a standard-reaching state, and if the liquid level is in the standard-reaching state, the step 4) is returned; if the liquid level is not in the standard reaching state, A-B & lt >. DELTA.Tup, the system confirms that the liquid level meets the standard reaching state, outputs a corresponding liquid level state signal, and returns to the step 4); if A-B is less than delta Tadp, the system replaces the liquid-free reference value A with (A + B)/2, stores and returns to the step 4); if A-B < DeltaTadp is not established, the system judges whether the continuous occurrence frequency of the counting state exceeds 50 times, if so, the system replaces the no-liquid reference value A with (A + B)/2, stores the no-liquid reference value A and returns to the step 4); if not, returning to the step 4);
(2) And if A = B: returning to the step 4);
(3) If A < B: the control chip unit judges whether the liquid level is in a standard-reaching state, if not, the (A + B)/2 is used for replacing the liquid-free reference value A, and the liquid level is stored and returned to the step 4); if the liquid level is in the standard reaching state, judging B-A > deltase:Sub>A Tdn, if the liquid level is in the standard reaching state, confirming that the liquid level does not meet the standard reaching state, outputting ase:Sub>A corresponding liquid level state signal, returning to the step 4), and if the liquid level is not in the standard reaching state, returning to the step 4).
2. The capacitive sensor liquid level detection method of claim 1, wherein a sensitivity adjustment capacitor for detecting sensitivity adjustment is provided in the capacitive detection unit.
3. The liquid level detection method of the capacitive sensor according to claim 1 or 2, wherein the liquid level detection end of the capacitive detection unit is formed by connecting a detection electrode T and a resistor R in series, and the other end of the resistor R is connected with a detection signal input end of the control chip unit.
4. The capacitive sensor liquid level detection method according to claim 1 or 2, characterized in that the control chip unit is a controller or a single chip with a capacitance detection function.
5. The capacitive sensor liquid level detection method of claim 1 or 2, wherein the output display unit is a display screen, a printing device, a light or a sound display device.
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| DE102018201421A1 (en) * | 2018-01-30 | 2019-08-01 | Brose Fahrzeugteile Gmbh & Co. Kommanditgesellschaft, Bamberg | Electronic control unit |
| CN108534865A (en) * | 2018-05-11 | 2018-09-14 | 上海航天设备制造总厂有限公司 | A kind of liquid level measuring system suitable for cryogenic liquid storage tank |
| CN108709604A (en) * | 2018-05-28 | 2018-10-26 | 浙江维思无线网络技术有限公司 | A kind of material level detection method and device |
| CN111060181A (en) * | 2019-12-23 | 2020-04-24 | 航天科技控股集团股份有限公司 | Liquid level measuring device based on capacitive sensor |
| CN113029287B (en) * | 2021-02-04 | 2024-02-02 | 惠州拓邦电气技术有限公司 | Water level detection method of coffee machine and coffee machine |
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