CN113532586A - Detection method of capacitive sensor - Google Patents
Detection method of capacitive sensor Download PDFInfo
- Publication number
- CN113532586A CN113532586A CN202110923443.8A CN202110923443A CN113532586A CN 113532586 A CN113532586 A CN 113532586A CN 202110923443 A CN202110923443 A CN 202110923443A CN 113532586 A CN113532586 A CN 113532586A
- Authority
- CN
- China
- Prior art keywords
- lmc555
- capacitive sensor
- power supply
- base chip
- gnd
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000001514 detection method Methods 0.000 title claims abstract description 26
- 239000003990 capacitor Substances 0.000 claims abstract description 20
- 230000010355 oscillation Effects 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 9
- 238000005259 measurement Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
Images
Classifications
-
- 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
- G01F23/266—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 measuring circuits therefor
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2605—Measuring capacitance
Abstract
The invention discloses a detection method of a capacitive sensor, which comprises the following steps: firstly, a detection circuit of a capacitive sensor is constructed, and a capacitor CX to be detected and a matched resistor R1 are connected to a trigger pin and a holding pin of a time-base chip LMC555 after forming an oscillation circuit; secondly, after the time base chip LMC555 is powered on, the power is input into a frequency capturing pin of the singlechip; thirdly, converting the acquired frequency into a capacitance value; and fourthly, determining the current capacitance value according to the proportional relation between the initial value and the final value of the capacitance value. The detection method can detect the measured capacitor without a high-precision ADC or a voltage comparator, and can greatly reduce the cost.
Description
[ technical field ] A method for producing a semiconductor device
The invention belongs to the technical field of sensor detection, and relates to a detection method of a capacitive sensor.
[ background of the invention ]
The capacitance type sensor is a sensor which is used more at present, changes of liquid level are described through capacitance continuous change values, the defect that a traditional magnetic turning plate cannot measure continuously can be overcome, and meanwhile, a single chip microcomputer module is required to have the capacity of measuring a tiny capacitance value.
Most of the existing capacitance detection methods are based on the charge and discharge of a capacitor, the voltage for starting the charge, the end voltage and the charge time are collected by an analog-to-digital conversion chip, and the measured capacitor is calculated according to a capacitance charge and discharge formula, and the method has several defects: (1) ADCs or voltage comparators with high precision are required; (2) the requirement on the timing precision is high, which brings higher cost, and the precision is not high when the capacitance is small, which leads to inaccurate measurement; (3) in a battery powered scenario, if power supply degradation occurs, the measured value may become larger.
[ summary of the invention ]
The invention provides a detection method of a capacitive sensor, which aims to solve the problems that a measured value is larger if power supply attenuation occurs in a battery power supply scene in the existing capacitance detection method.
In order to solve the technical problems, the invention adopts the following technical scheme.
A detection method of a capacitive sensor comprises the following steps:
firstly, a detection circuit of a capacitive sensor is constructed, and a capacitor CX to be detected and a matched resistor R1 are connected to a trigger pin and a holding pin of a time-base chip LMC555 after forming an oscillation circuit;
secondly, after the time base chip LMC555 is powered on, the power is input into a frequency capturing pin of the singlechip;
thirdly, converting the acquired frequency into a capacitance value;
and fourthly, determining the current capacitance value according to the proportional relation between the initial value and the final value of the capacitance value.
Further, the detection circuit of the capacitive sensor comprises a power supply cathode GND, a power supply anode VCC, a time base chip LMC555, a resistor R1, a capacitor C1 and a measured capacitor CX.
Further, the power negative electrode GND comprises a first power negative electrode GND, a second power negative electrode GND and a third power negative electrode GND.
Further, the voltage of the power supply cathode GND is 0V.
Furthermore, the voltage of the power supply anode VCC is 2.5-5.5V.
Further, the time base chip LMC555 includes 8 pins.
Further, the resistor R1 is 10K.
Further, the capacitance C1 is 100 nF.
Compared with the existing capacitance detection method, the detection method has the following advantages:
(1) the capacitance value of the sensor can be continuously measured, so that the liquid level sensors are not discrete numerical values any more;
(2) the detection method can detect the measured capacitor without a high-precision ADC or a voltage comparator, and can greatly reduce the cost;
(3) the existing capacitance detection method has high requirement on the precision of timing, which brings higher cost, and the precision is not high when the capacitance is smaller, so that the measurement is inaccurate, but the invention can still keep higher measurement precision when the capacitance is smaller;
(4) the detection circuit of the invention is not influenced by the power supply voltage, can keep good precision within a certain voltage range, and is more accurate than the test method of the existing capacitance detection method.
[ description of the drawings ]
Fig. 1 is a schematic diagram of a detection circuit of the capacitive sensor according to the present invention.
[ detailed description ] embodiments
The present invention will be described in further detail with reference to the following detailed description and accompanying drawings. It should be emphasized that the following description is merely exemplary in nature and is not intended to limit the scope of the invention or its application.
Examples
Referring to fig. 1, the pin numbers, codes and connection relationships of the time-base chip are shown in the following table:
from FIG. 1, the component numbers, meanings and specifications are as follows:
| reference numerals | Means of | Specification of |
| GND | Negative pole of power supply | 2.5-5.5V power supply cathode |
| VCC | Power supply anode | 2.5-5.5V power supply anode |
| IC-8-LMC555 | Time base chip | LMC555 |
| R1 | Resistance (RC) | 10K, 0603 package |
| C1 | Capacitor 104 | 100nF, 0603 package |
| CX | Measured capacitance | Sensor capacitance |
As shown in fig. 1, a detection circuit of a capacitive sensor includes a power supply cathode GND, a power supply anode VCC, a time base chip LMC555, a resistor R1, a capacitor C1, and a measured capacitor CX; the power supply cathode GND comprises a first power supply cathode GND, a second power supply cathode GND and a third power supply cathode GND; the negative pole GND of the first power supply is connected with an eighth pin GND of the time base chip LMC 555; a first pin V + of the time-base chip LMC555 is connected with a power supply anode VCC and one end of a capacitor C1; the other end of the capacitor C1 is connected with the cathode GND of the second power supply; a seventh pin TRI of the time-base chip LMC555 is a trigger pin and is connected with one end of the capacitor CX to be detected; the other end of the capacitor CX to be detected is connected with a third power supply cathode GND; a sixth pin OUT of the time base chip LMC555 is a frequency capture pin and is connected with one end of a resistor R1; the other end of the resistor R1 is connected with the capacitor CX to be tested, a third pin of the time base chip LMC555 and a seventh pin of the time base chip LMC 555; the third pin of the time base chip LMC555 is an input holding pin; and the seventh pin of the time base chip LMC555 is a trigger pin.
The detection method of the capacitive sensor comprises the following steps:
firstly, a detection circuit of a capacitive sensor is constructed, and a capacitor CX to be detected and a matched resistor R1 are connected to a trigger pin and a holding pin of a time-base chip LMC555 after forming an oscillation circuit;
secondly, after the time base chip LMC555 is powered on, the power is input into a frequency capturing pin of the singlechip;
thirdly, converting the acquired frequency into a capacitance value;
and fourthly, determining the current capacitance value according to the proportional relation between the initial value and the final value of the capacitance value.
The time base chip LMC555 used in the method is a time base chip with low price and low power consumption, a square wave pulse is formed on a sixth pin OUT of the time base chip LMC555 by utilizing the matching of a resistor R1 and a measured capacitor CX, after power is supplied to a power supply anode VCC, a pulse port can output a pulse with a fixed duty ratio of 50%, the amplitude is as high as the power supply anode VCC, and thus CX 1/(1.4fR) can be measured, wherein f is the frequency of output pulse, R is R1, and 10K is taken.
The following data were actually measured:
through determination, the capacitance value has obvious resolution within the whole range of 2-1500 pF (see the following table), and the frequency value can be correctly read by using the timer capture function of a common single chip microcomputer, so that the corresponding capacitance value is calculated.
Through tests, the above table shows that the precision can be kept well within the power supply voltage of 2.5-5.5V of the battery, and the influence of the attenuation of a power supply is avoided.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A detection method of a capacitive sensor is characterized by comprising the following steps:
firstly, a detection circuit of a capacitive sensor is constructed, and a capacitor CX to be detected and a matched resistor R1 are connected to a trigger pin and a holding pin of a time-base chip LMC555 after forming an oscillation circuit;
secondly, after the time base chip LMC555 is powered on, the power is input into a frequency capturing pin of the singlechip;
thirdly, converting the acquired frequency into a capacitance value;
and fourthly, determining the current capacitance value according to the proportional relation between the initial value and the final value of the capacitance value.
2. The method according to claim 1, wherein the detection circuit of the capacitive sensor comprises a power supply cathode GND, a power supply anode VCC, a time-base chip LMC555, a resistor R1, a capacitor C1, and a measured capacitance CX.
3. The detecting method of the capacitive sensor as claimed in claim 2, wherein the power negative electrodes GND includes a first power negative electrode GND, a second power negative electrode GND and a third power negative electrode GND.
4. The method as claimed in claim 3, wherein the voltage of the power supply cathode GND is 0V.
5. The method as claimed in claim 2, wherein the voltage of the positive electrode VCC of the power supply is 2.5-5.5V.
6. The method as claimed in claim 2, wherein the time base chip LMC555 comprises 8 pins.
7. The method as claimed in claim 2, wherein the resistance R1 is 10K.
8. The method as claimed in claim 2, wherein said capacitance C1 is 100 nF.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110923443.8A CN113532586A (en) | 2021-08-12 | 2021-08-12 | Detection method of capacitive sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110923443.8A CN113532586A (en) | 2021-08-12 | 2021-08-12 | Detection method of capacitive sensor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN113532586A true CN113532586A (en) | 2021-10-22 |
Family
ID=78090997
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110923443.8A Pending CN113532586A (en) | 2021-08-12 | 2021-08-12 | Detection method of capacitive sensor |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113532586A (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004170163A (en) * | 2002-11-19 | 2004-06-17 | Mitsutoyo Corp | Electrostatic capacity type displacement sensor |
| CN206684233U (en) * | 2017-03-24 | 2017-11-28 | 湖北工程学院 | Capacitance measurement circuit and device |
| CN108196129A (en) * | 2018-01-05 | 2018-06-22 | 电子科技大学 | A kind of capacitance measuring device |
| CN111650443A (en) * | 2020-07-02 | 2020-09-11 | 深圳市诺心信息科技有限公司 | Simple capacitance value measuring circuit and method |
| CN215415624U (en) * | 2021-08-12 | 2022-01-04 | 矽朋微电子(无锡)有限公司 | Detection circuit of capacitive sensor |
-
2021
- 2021-08-12 CN CN202110923443.8A patent/CN113532586A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004170163A (en) * | 2002-11-19 | 2004-06-17 | Mitsutoyo Corp | Electrostatic capacity type displacement sensor |
| CN206684233U (en) * | 2017-03-24 | 2017-11-28 | 湖北工程学院 | Capacitance measurement circuit and device |
| CN108196129A (en) * | 2018-01-05 | 2018-06-22 | 电子科技大学 | A kind of capacitance measuring device |
| CN111650443A (en) * | 2020-07-02 | 2020-09-11 | 深圳市诺心信息科技有限公司 | Simple capacitance value measuring circuit and method |
| CN215415624U (en) * | 2021-08-12 | 2022-01-04 | 矽朋微电子(无锡)有限公司 | Detection circuit of capacitive sensor |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US7145350B2 (en) | Process and a circuit arrangement for evaluating a measuring capacitance | |
| CN101359011B (en) | Circuit for measuring micro-change of capacitance | |
| CN215415624U (en) | Detection circuit of capacitive sensor | |
| CN105527501A (en) | Small capacitance measurement method | |
| CN108918980A (en) | A kind of capacitance signal measuring circuit and measurement method | |
| CN103148953A (en) | Temperature detecting circuit based on thermistor | |
| CN202404157U (en) | Circuit for detecting variable resistance value based on I/O port | |
| CN113532586A (en) | Detection method of capacitive sensor | |
| CN201215570Y (en) | Voltage detecting circuit for battery | |
| CN110133528A (en) | A kind of the internal resistance measurement device and its measurement method of automatic measure on line lithium battery | |
| CN112180176A (en) | Capacitance value measuring circuit and method based on constant current source | |
| TWI645200B (en) | Non-contact static electricity measuring device | |
| JP5039169B2 (en) | Capacitance detection device, resistance detection device | |
| US20030042910A1 (en) | Method and circuit for electrical testing of isolation resistance of large capacitance network | |
| Reverter et al. | Direct interface circuit for differential capacitive sensors | |
| CN220153731U (en) | Sensor access detection unit based on weighing instrument | |
| CN220730412U (en) | Magnetic measuring sensor selecting instrument | |
| CN217425555U (en) | Capacitor storage capacity measuring circuit | |
| CN219320457U (en) | Battery electricity meter chip and electronic equipment with same | |
| CN218037070U (en) | Capacitance measurement chip, universal meter and capacitance measurement circuit | |
| CN216012401U (en) | Liquid level detecting device | |
| CN216248915U (en) | Metering device for 16-way ignition delay time of program controller detection equipment | |
| CN214748285U (en) | Liquid level detecting device | |
| US11906559B2 (en) | Enhanced impedance measurement using CTMU | |
| CN220207733U (en) | Circuit for preventing voltage measurement error and air conditioner |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |