CN219348717U - Humidity sensor of humidity-sensitive capacitor - Google Patents
Humidity sensor of humidity-sensitive capacitor Download PDFInfo
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- CN219348717U CN219348717U CN202320159517.XU CN202320159517U CN219348717U CN 219348717 U CN219348717 U CN 219348717U CN 202320159517 U CN202320159517 U CN 202320159517U CN 219348717 U CN219348717 U CN 219348717U
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Abstract
The utility model discloses a humidity sensor of a humidity-sensitive capacitor, which relates to the technical field of humidity sensors and aims at solving the problem that the distribution capacitance of the existing measurement connecting circuit affects the measured capacitance and the measurement precision of the sensor is low. The humidity sensor of the humidity sensitive capacitor can effectively avoid the influence of the distributed capacitance of the measurement connection circuit on the measured capacitance, and meanwhile, the high-precision voltage measurement accurate to the uV level is realized by adopting a secondary sampling method, so that the production cost is reduced, and the use is convenient.
Description
Technical Field
The utility model relates to the technical field of humidity sensors, in particular to a humidity sensor with a humidity sensor capacitor.
Background
The capacitance type humidity sensor is based on accurate high-resolution measurement of humidity-sensitive capacitance along with temperature change, and measurement of small change of humidity-sensitive capacitance is a relatively complex and troublesome problem, and many factors such as distributed capacitance, lead capacitance, electromagnetic interference, signal leakage, circuit drift can seriously influence measurement results, and are difficult to eliminate, and a traditional capacitance type humidity sensor measurement circuit comprises: in addition, the accuracy of the measurement result depends on the stability of the power supply voltage, so in order to solve the problems, we propose a humidity sensor of humidity sensitive capacitance.
Disclosure of Invention
The humidity sensor of the humidity sensitive capacitor solves the problems that the measured capacitance is influenced by the distributed capacitance of the measurement connecting circuit and the measurement accuracy of the sensor is low.
In order to achieve the above purpose, the present utility model adopts the following technical scheme:
the humidity sensor comprises a shell, wherein an MCU is arranged at the top end of the shell, a threaded mounting block is arranged at the top end of the MCU, a protection tube is arranged at the top end of the threaded mounting block, a switch circuit module, an integrating circuit module, a differential synthesis module, a potential translation module and an output amplification module are arranged in the protection tube, one end of the switch circuit module is electrically connected with the MCU, the other end of the switch circuit module is electrically connected with the integrating circuit module, the integrating circuit module is electrically connected with the differential synthesis module, the differential synthesis module is electrically connected with the potential translation module, the potential translation module is electrically connected with the output amplification module, the other end of the output amplification module is electrically connected with the MCU, and the differential synthesis module and the potential translation module are electrically connected with the MCU; the MCU provides a control signal V sw1 、V sw2 For V 1 Voltage AD conversion, extracting voltage part larger than 1mV, collecting V 1 Is greater than 1mV of the partial voltageThe DA conversion is sent to a potential translation module for operation to realize V 1 Is shifted to V 2 Output voltage V to the output amplifying module 3 AD conversion is performed according to V 3 Is calibrated to calculate the capacitance C causing humidity 6 Humidity value with varying capacitance.
Preferably, the top of protection tube is provided with the bleeder vent, the bottom of casing is provided with the pin terminal, the pin terminal is the symmetry setting with the axis of casing, the inner wall of protection tube is provided with the ceramic sleeve.
Preferably, the switch circuit module adopts a 4-analog switch circuit IC and is connected with a humidity-sensitive capacitor C to be tested 6 The switch circuit module is connected with the integrating circuit module and the MCU, the MCU provides control signals for the switch circuit module, and the tested capacitor C6 is charged and discharged.
Preferably, the switch circuit module can adopt 1 piece of 4 analog switch integrated circuits or 2 pieces of 2 analog switch integrated circuits.
Preferably, the integrating circuit module comprises two operational amplifier integrating circuits U with discharge loops 1A And U 1D Is formed by U 1A Charging integrating circuit for tested capacitor, U 1D The discharging integrating circuit is used for discharging the tested capacitor.
Preferably, the differential synthesis module is a differential amplification circuit composed of an operational amplifier, and outputs the voltage V of the integration circuit module two positive and negative C1 And V is equal to C4 Subtracting and synthesizing an output voltage V 1 。
Preferably, the potential shift module is a differential amplifying circuit composed of an operational amplifier, and subtracts a voltage part greater than 1mV from V1, and retains a part less than 1 mV.
Preferably, the output amplifying module is an inverting amplifier formed by an operational amplifier, the output voltage of the circuit of the potential translation module is amplified to the magnitude of 10mV, the input impedance is more than 100MΩ, and the open-loop gain is more than 10000 times.
Preferably, the operational amplifier integrated circuit is any one of a single operational amplifier integrated circuit, a dual operational amplifier integrated circuit, a three operational amplifier integrated circuit and a four operational amplifier integrated circuit.
Preferably, the MCU is a singlechip integrated circuit which is provided with more than 3 paths of ADC conversion circuits and more than one path of DAC conversion circuits and can generate a pair of reverse waveforms with the frequency more than or equal to 50 KHZ.
The beneficial effects of the utility model are as follows:
1. the utility model charges and discharges the tested capacitor through switch control, and can realize the integration of the charge and discharge by two operational amplifier integrating circuits respectively until each charge of the integrating capacitor of the integrating circuit and RC discharge of the integrating feedback circuit reach balance, thereby avoiding the influence of the distributed capacitor of the measuring connection circuit on the tested capacitor and realizing 10 measuring resolution -4 PF。
2. The utility model utilizes the 12-bit AD circuit and the DA circuit of the MCU, can realize the high-precision voltage measurement which is accurate to the uV level by adopting a secondary sampling method, reduces the cost and also reduces the complexity of a hardware circuit.
In summary, the device can effectively avoid the influence of the distributed capacitance of the measurement connection circuit on the measured capacitance, and meanwhile, the method of secondary sampling is adopted to realize high-precision voltage measurement accurate to the uV level, so that the production cost is reduced, and the use is convenient.
Drawings
Fig. 1 is a schematic structural view of the present utility model.
Fig. 2 is a schematic view of the internal structure of the housing of the present utility model.
Fig. 3 is a schematic diagram of the overall circuit structure of the present utility model.
Fig. 4 is a schematic diagram of a switch circuit structure according to the present utility model.
Fig. 5 is a schematic diagram of an integrating circuit according to the present utility model.
Fig. 6 is a schematic diagram of a differential synthesis circuit according to the present utility model.
Fig. 7 is a schematic diagram of a potential shift circuit according to the present utility model.
Fig. 8 is a schematic diagram of an output amplifying circuit according to the present utility model.
Fig. 9 is a schematic diagram of a switch linkage structure according to the present utility model.
Reference numerals in the drawings: 1. a housing; 2. an MCU; 3. a threaded mounting block; 4. a protective tube; 5. ventilation holes; 6. a pin terminal; 7. a switching circuit module; 8. an integrating circuit module; 9. a differential synthesis module; 10. a potential translation module; 11. an output amplification module; 12. a ceramic sleeve.
Detailed Description
The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments.
Referring to fig. 1-9, a humidity sensor of humidity sensor comprises a housing 1, an MCU2 (single chip microcomputer) is arranged at the top end of the housing 1, a screw thread mounting block 3 is arranged at the top end of the MCU2, a protection tube 4 is arranged at the top end of the screw thread mounting block 3, a switch circuit module 7, an integrating circuit module 8, a differential synthesis module 9, a potential translation module 10 and an output amplification module 11 are arranged inside the protection tube 4, one end of the switch circuit module 7 is electrically connected with the MCU2, the other end of the switch circuit module 7 is electrically connected with the integrating circuit module 8, the integrating circuit module 8 is electrically connected with the differential synthesis module 9, the differential synthesis module 9 is electrically connected with the potential translation module 10, the potential translation module 10 is electrically connected with the output amplification module 11, the other end of the output amplification module 11 is electrically connected with the MCU2, the differential synthesis module 9 and the potential translation module 10 are electrically connected with the MCU2, an air vent 5 is arranged at the top end of the protection tube 4, a pin terminal 6 is arranged at the bottom end of the housing 1, the pin terminal 6 is symmetrically arranged with the central axis of the housing 1, and a ceramic sleeve 12 is arranged on the inner wall of the protection tube 4.
As shown in fig. 3, 4 and 5, the switch circuit module 7 adopts a 4-analog switch circuit IC and is connected with a humidity-sensitive capacitor C to be measured 6 The switch circuit module 7 is connected with the integrating circuit module 8 and the MCU2, the MCU2 provides control signals for the switch circuit module 7, the tested capacitor C6 is charged and discharged, and the switch circuit module 7 can adopt 1 piece 4 analog switchesThe integrated circuit can also adopt 2 pieces of 2 analog switch integrated circuits, the integrating circuit module 8 is composed of two parts, U 1A For charging the integrating circuit, U 1D For discharging the integrating circuit, the resistance and capacitance values in the circuit are not unique, and can be adjusted arbitrarily within a certain range, the differential synthesis module 9 is a typical differential operation circuit, and the output voltages V of the two integrating circuit modules 8 are obtained C1 The difference between the voltage and VC4 (actually, absolute value addition) is synthesized into an output voltage V1, the resistance and capacitance values in the circuit are not unique and can be arbitrarily adjusted within a certain range, the potential shift module 10 is also a typical differential operation circuit, a voltage part larger than 1mV is subtracted from V1, a part smaller than 1mV is reserved, the voltage is moved downwards to be lower than 1mV, the resistance and capacitance values in the circuit are not unique and can be arbitrarily adjusted within a certain range, the output amplification module 11 is formed by a typical inverting amplifier consisting of an operational amplifier, the output voltage of the potential shift circuit is amplified to be in the order of 10mV, the voltage smaller than 1mV is amplified by 60dB, the resistance and capacitance values in the circuit are not unique and can be arbitrarily adjusted within a certain range, and the input impedance is input>100MΩ, open loop gain>10000 times, the working power supply meets the following conditions: the negative power supply is less than or equal to-3V, and the positive power supply is less than or equal to +3V. The operational amplifier integrated circuit may be a single operational amplifier integrated circuit, a double operational amplifier integrated circuit, a three operational amplifier integrated circuit or a four operational amplifier integrated circuit;
MCU2 (single chip microcomputer) is used for providing control signal V sw1 、V sw2 For V 1 Voltage AD conversion, extracting voltage part larger than 1mV, collecting V 1 The partial voltage of which the voltage is larger than 1mV is sent to the potential translation module 10 for operation through DA conversion, thus realizing V 1 Is shifted to V 2 Output voltage V to output amplification module 11 3 AD conversion is performed according to V 3 Is calibrated to calculate the capacitance C causing humidity 6 Humidity value with varying capacitance.
Working principle: when in use, the device is connected, the charging and discharging of the capacitor to be tested are controlled by the switch circuit module 7, the charging and discharging are respectively integrated by the two operational amplifier integrating circuit modules 8,until each charge of the integrating capacitor of the integrating circuit module 8 and the discharge of the integrating feedback circuit RC reach equilibrium, then the output voltage difference of the two integrating circuit modules 8 is measured, and the device is tested by theoretical calculation and simulation 10 -4 The capacitance change of pF corresponds to the voltage difference change of several uV, and the detection by using 12-bit AD conversion sampling obviously leads to larger sampling error, so that the subsampling method is adopted, the first AD conversion only detects mV-level voltage, then DA conversion is added into source voltage analog subtraction operation so as to lead the original voltage to be left<10 -3 V, amplifying the residual voltage by 60DB, detecting the secondary AD conversion sample, accurately measuring the tiny voltage change, and calibrating the tiny voltage change as humidity change;
in the circuit: when the power circuit module 7S is switched on and off 1A And S is equal to 1C Linkage is formed by V SW1 Control, S 1B And S is equal to 1D Linkage is formed by V SW2 Control, V SW1 And V is equal to SW2 Opposite phase (as in FIG. 9), S 1A 、S 1C When closed, S 1B 、S 1D Disconnection, or vice versa;
when the power circuit module 7S is switched on and off 1A 、S 1C Closure S 1B 、S 1D During the off period V CC (5V) pair C 6 Inter-charging to V CC C because of high-resistance virtual ground of the operational amplifier input end 1 The same amount of charge is accumulated in the moment to generate voltage V c1 (<0) During this time C4 discharges through R9;
when the power circuit module 7S is switched on and off 1B 、S 1D Closure S 1A 、S 1C During the off period C 6 Is discharged to 0 from ground, C is due to the high-resistance virtual ground of the operational amplifier input end 4 The same amount of charge is accumulated in the moment to generate voltage V c4 (>0) During this period C1 discharges through R1;
when the switch power circuit module 7 is powered on, the power supply is turned on for C 6 C (C) charge and discharge 1 、C 4 The voltage on the capacitor gradually rises, each period C 1 、C 4 The charge amount is the same, and the discharge follows V C1 And V is equal to C4 The rise gradually increases, so that each of thePeriod C 1 、C 4 Is balanced with the charge and discharge of C 1 、C 4 Voltage V on C1 And V is equal to C4 No longer rise, v1=v C1 -V C4 Proportional to C 6 Capacitance value, C 1 、C 4 Size and C of (2) 6 The larger the ratio of the ratio is, the slower the measurement speed is, and the higher the measurement accuracy is;
when MCU2 pairs V 1 AD conversion is carried out to obtain mV-level precision, and then accurate DA inverse conversion is carried out to obtain V 1m . Doing operation V 2 ＝V 1 -V 1m ；V 3 ＝A*V 2 (A is the gain of a precision amplifier), then AD conversion is carried out on V3, and the result is converted into a humidity signal through calibration calculation, so that the measurement precision is improved;
the circuit parameters are approximately desirable DeltaV 1/DeltaC 6 ＝25.000*10 -3 The rate of change of V/p, i.e. every 10 increases in capacitance -4 pF，V 1 Increase 2.5uV, thus measuring V 1 The change in microvolt level can be measured to determine the humidity induced humidity sensor 10 -4 Capacitance variation of pF stage, C 6 Left end charging connection V CC (5V), discharge is grounded, so that the distributed capacitance on the connection line at the left end of CH has no influence on CH measurement, C 6 The right end charge and discharge are all virtual ground, and the voltage is not absolute 0, so that the method has some influence on the test result, namely about 4uV/10P, and the influence of the distributed capacitance of the measurement connection circuit on the tested capacitance can be effectively reduced.
The present utility model is not limited to the above-mentioned embodiments, and any person skilled in the art, based on the technical solution of the present utility model and the inventive concept thereof, can be replaced or changed within the scope of the present utility model.
Claims (10)
1. The utility model provides a humidity sensor of humidity-sensitive capacitance, includes casing (1), its characterized in that, the top of casing (1) is provided with MCU (2), the top of MCU (2) is provided with screw thread installation piece (3), the top of screw thread installation piece (3) is provided with protection tube (4), the inside of protection tube (4) is provided with switch circuit module (7), integration circuit module (8), difference synthesis module (9), potential translation module (10) and output amplification module (11), the one end of switch circuit module (7) links to each other with MCU (2) electrical property, just the other end and the integration circuit module (8) electrical property of switch circuit module (7) link to each other, integration circuit module (8) link to each other with difference synthesis module (9) electrical property, just difference synthesis module (9) link to each other with potential translation module (10) electrical property, potential translation module (10) link to each other with output amplification module (11) electrical property, the other with MCU (2) electrical property of the other, difference synthesis module (9) and MCU (2) electrical property.
2. The humidity sensor of claim 1 wherein the top end of the protection tube (4) is provided with ventilation holes (5), the bottom end of the housing (1) is provided with pin terminals (6), the pin terminals (6) are symmetrically arranged with the central axis of the housing (1), and the inner wall of the protection tube (4) is provided with a ceramic sleeve (12).
3. A humidity sensor according to claim 1 characterized in that the switch circuit module (7) adopts a 4-analog switch circuit IC and is connected with a humidity sensor C to be measured 6 The switch circuit module (7) is connected with the integrating circuit module (8) and the MCU (2).
4. A humidity sensor according to claim 3 characterized in that the switching circuit module (7) employs 1 chip 4 analog switching integrated circuit or 2 chip 2 analog switching integrated circuit.
5. A humidity sensor according to claim 1 characterized in that the integrating circuit module (8) consists of two operational amplifier integrating circuits U with discharge loops 1A And U 1D Is formed by U 1A Charging integrating circuit for tested capacitor, U 1D The discharging integrating circuit is used for discharging the tested capacitor.
6. A humidity sensor according to claim 1 characterized in that the differential synthesizing module (9) is a differential amplifying circuit composed of an operational amplifier for integrating the output voltages V of the circuit module (8) two positive and one negative C1 And V is equal to C4 Subtracting and synthesizing an output voltage V 1 。
7. A humidity sensor according to claim 1 wherein the potential shift module (10) is a differential amplifier circuit comprising an operational amplifier, subtracting the voltage fraction greater than 1mV from V1, leaving the fraction less than 1 mV.
8. A humidity sensor according to claim 1 characterized in that the output amplification module (11) is an inverting amplifier formed by an operational amplifier, amplifying the circuit output voltage of the potential translation module (10) to the order of 10mV, input impedance >100mΩ, open loop gain >10000 times.
9. The humidity sensor of claim 8 wherein the operational amplifier integrated circuit is any one of a single operational amplifier integrated circuit, a dual operational amplifier integrated circuit, a three operational amplifier integrated circuit, and a four operational amplifier integrated circuit.
10. The humidity sensor of claim 1 wherein the MCU (2) is a single chip integrated circuit having more than 3 ADC conversion circuits, one or more DAC conversion circuits capable of generating a pair of reverse waveforms at a frequency of 50KHZ or more.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320159517.XU CN219348717U (en) | 2023-02-09 | 2023-02-09 | Humidity sensor of humidity-sensitive capacitor |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320159517.XU CN219348717U (en) | 2023-02-09 | 2023-02-09 | Humidity sensor of humidity-sensitive capacitor |
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| CN219348717U true CN219348717U (en) | 2023-07-14 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116203084A (en) * | 2023-02-09 | 2023-06-02 | 广州海谷电子科技有限公司 | Method for realizing humidity-sensitive capacitance sensor based on switch capacitance measurement and sensor |
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2023
- 2023-02-09 CN CN202320159517.XU patent/CN219348717U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116203084A (en) * | 2023-02-09 | 2023-06-02 | 广州海谷电子科技有限公司 | Method for realizing humidity-sensitive capacitance sensor based on switch capacitance measurement and sensor |
| CN116203084B (en) * | 2023-02-09 | 2024-01-23 | 广州海谷电子科技有限公司 | Method for realizing humidity-sensitive capacitance sensor based on switch capacitance measurement and sensor |
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