WO2019174123A1

WO2019174123A1 - Intelligent humidity sensor

Info

Publication number: WO2019174123A1
Application number: PCT/CN2018/087817
Authority: WO
Inventors: 杜伟略; 刘新平; 平毅; 谈向萍; 肖国玲
Original assignee: 无锡职业技术学院
Priority date: 2018-03-15
Filing date: 2018-06-14
Publication date: 2019-09-19
Also published as: CN108536053B; CN108536053A

Abstract

An intelligent humidity sensor, wherein the structure thereof comprises that a first signal output terminal of a humidity sensor sampling circuit (001) is connected to a first signal input terminal of an amplification control circuit (002); a second signal output terminal of the humidity sensor sampling circuit (001) is connected to a signal input terminal of an A/D conversion pre-input circuit (004); a signal output terminal of the A/D conversion pre-input circuit (004) is connected to a first signal input terminal of a single-chip computer system (005); a second signal input terminal of the single-chip computer system (005) is connected to a signal output terminal of a human-machine dialogue unit (007); a third signal input terminal of the single-chip computer system (005) is connected to a signal output terminal of an A/D conversion pre-output circuit (006); a first signal input and output terminal of the single-chip computer system (005) is connected to a signal input and output terminal of the amplification control circuit (002); and a signal output terminal of the amplification control circuit (002) is connected to a signal input terminal of the A/D conversion pre-output circuit (006).

Description

Intelligent humidity sensor

Technical field

The invention relates to an intelligent humidity sensor, belonging to the technical field of sensors.

Background technique

In recent years, with the rapid development of artificial intelligence and big data, smart sensors are the front-end of data, and the demand for smart sensors is relatively large. In the production of sensors, the consistency and stability of humidity sensors are not high, and they need to be needed every year. Maintenance; when the humidity sensor converts the non-electricity into the standard 0~5V, it is necessary to carry out the conditioning circuit through the transmitter for finishing. In the past, the two zero potentiometers were manually adjusted repeatedly to adjust the zero point and enlargement of the amplifying circuit. Multiples, which leads to problems such as low production efficiency and inconsistent precision.

Summary of the invention

The invention provides an intelligent humidity sensor, the purpose of which is to provide a humidity sensor which can realize the adjustment of the amplification and zero point control circuit parameters by simple manual operation.

The technical solution of the invention is an intelligent humidity sensor, the structure thereof comprises a humidity sensor sampling circuit 001, an amplification control circuit 002, an A/D conversion pre-input circuit 004, a single-chip system 005, an A/D conversion pre-output circuit 006 The human-machine dialogue unit 007; wherein the first signal output end of the humidity sensor sampling circuit 001 is connected to the first signal input end of the amplification control circuit 002, and the second signal output end of the humidity sensor sampling circuit 001 is before the A/D conversion The signal input end of the input circuit 004 is connected, and the signal output end of the A/D conversion pre-input circuit 004 is connected to the first signal input end of the single chip system 005, and the second signal input end of the single chip system 005 and the human-machine dialogue unit 007 The signal output end is connected, the third signal input end of the single chip system 005 is connected with the signal output end of the A/D conversion pre-output circuit 006, and the signal input and output of the first signal input and output end of the single chip system 005 and the amplification control circuit 002 Connected to the terminal, the signal output terminal of the amplification control circuit 002 is connected to the signal input terminal of the A/D conversion preamplifier circuit 006.

Advantages of the invention:

1) The whole system has monitoring points at input VIN and output VO, and forms closed-loop control with single-chip microcomputer system and amplification control circuit, which is convenient to join various algorithm control;

2) The technical difficulty of the debugging personnel is reduced, the repeated process of manually adjusting the potentiometer is omitted, and the debugging precision is improved;

3) Improved production process and work efficiency;

4) At the same time, in order to expand the application range of the smart sensor, increase the communication interface, if the communication interface is connected to the wifi module. Remote maintenance is also possible.

DRAWINGS

Figure 1 is a schematic view of the structure of the present invention.

2 is a schematic structural view of a humidity sensor sampling circuit 001.

3 is a schematic structural view of an amplification control circuit 002.

4 is a schematic structural view of an A/D conversion pre-input circuit 004.

FIG. 5 is a schematic structural view of the A/D conversion pre-output circuit 006.

FIG. 6 is a schematic diagram of the workflow of the single chip system 005.

FIG. 7 is a schematic structural diagram of the human-machine dialog unit 007.

FIG. 8 is a schematic structural diagram of the interface module 008.

In the drawing, 001 is the humidity sensor sampling circuit, 002 is the amplification control circuit, 003 is the drive output circuit, 004 is the A/D conversion pre-input circuit, 005 is the single-chip system, 006 is the A/D conversion pre-output circuit, 007 It is a human-machine dialogue unit, and 008 is an interface module.

detailed description

An intelligent humidity sensor, the structure comprises a humidity sensor sampling circuit 001, an amplification control circuit 002, an A/D conversion pre-input circuit 004, a single-chip system 005, an A/D conversion pre-output circuit 006, a human-machine dialogue unit 007; The first signal output end of the humidity sensor sampling circuit 001 is connected to the first signal input end of the amplification control circuit 002, the second signal output end of the humidity sensor sampling circuit 001 and the signal input of the A/D conversion pre-input circuit 004. Connected to the end, the signal output end of the A/D conversion pre-input circuit 004 is connected to the first signal input end of the single-chip system 005, and the second signal input end of the single-chip system 005 is connected to the signal output end of the human-machine dialog unit 007, the single-chip microcomputer The third signal input end of the system 005 is connected to the signal output end of the A/D conversion pre-output circuit 006, and the first signal input and output end of the single chip system 005 is connected to the signal input and output end of the amplification control circuit 002, and the amplification control circuit 002 The signal output terminal is connected to the signal input terminal of the A/D conversion pre-output circuit 006.

The intelligent humidity sensor further includes an interface module 008, and the signal input and output end of the interface module 008 is connected to the second signal input and output end of the single chip system 005.

Referring to FIG. 2, the humidity sensor sampling circuit 001 includes a polymer humidity sensor (RH), and the polymer humidity sensor adopts a polymer resistance type humidity sensor of Shenzhen Meiterui Technology Development Co., Ltd.; In the sensor sampling circuit 001, a typical RC bridge oscillator circuit is formed by R20 resistor, C31 capacitor, C32 capacitor, R22 resistor, R23 resistor, R24 resistor and op amp U2A, and a sine wave with a frequency of 1KHz and an amplitude of 1V is generated as a polymer. The humidity sensor provides power supply. In order to reduce the influence of the rear circuit on the front circuit, the first-stage operational amplifier U2B is added to function as an impedance isolation. In order to reduce the influence of the latter circuit on the front circuit, another stage of the operational amplifier U2C is added, and the isolation is performed. Function; C33 capacitor is a DC blocking capacitor; polymer humidity sensor (RH) is divided with RT resistor and W3 resistor, RT is temperature compensating resistor, AC amplification is performed by another stage U2C, and diode D4 acts as half-wave rectification. Finally, the R5 resistor and the C30 capacitor are first-order filtering, and the alternating current is converted into a direct current; the first signal output end of the humidity sensor sampling circuit 001, the second The signal output end inputs the same sampling voltage VIN to the signal input end of the first signal input end of the amplification control circuit 002 and the A/D conversion pre-input circuit 004, respectively; the first signal output end of the humidity sensor sampling circuit 001, The second signal output is a common output.

Referring to FIG. 3, the amplification control circuit 002 includes a transmitter amplifying circuit, a zero point control circuit, and a driving output circuit 003. The transmitter amplifying circuit uses a negative feedback operational amplifier amplifying circuit U2D to improve the digital potentiometer adjustment accuracy. The W2 programmable potentiometer and the R4 resistor are feedback resistors for adjusting the amplification factor. The transmitter amplifying circuit is mainly for satisfying the output of the intelligent humidity sensor to reach 5V; the zero point control circuit adopts a typical operational amplifier summation. The circuit, the operational amplifier summation circuit comprises a positive polarity circuit and a negative polarity circuit; the negative polarity circuit is a sampling voltage VIN outputted by the first signal output end of the humidity sensor sampling circuit 001, and is connected to the negative feedback through the R9 resistor. Negative terminal of the operational amplifier amplifier circuit U2D; positive polarity circuit includes 12V voltage terminal, W1 programmable potentiometer, R2 resistor, R3 resistor, analog ground, 12V voltage terminal is connected with external 12V power supply, W1 programmable potentiometer center taps through The R11 resistor is also connected to the negative terminal of the negative feedback op amp amplifier circuit U2D. As long as the resistance of the R9 resistor and the R11 resistor are equal, then the negative feedback op amp amplifier circuit The input voltage of U2D is the sum of the two. The function of the W1 programmable potentiometer is to adjust the low point of the voltage of the drive output circuit 003.

The W1 programmable potentiometer and the W2 programmable potentiometer all use a digital potentiometer x9110.

The driving output circuit 003 adopts an emitter follower, preferably a triode emitter follower output, to increase driving capability and impedance isolation; the voltage of the emitter of the transistor Q1 in FIG. 3 is VO.

Referring to FIG. 4, the A/D conversion pre-input circuit 004 adopts the LM358 op amp for inverting amplification. If the resistance values of R29 and R30 are equal, the circuit functions as the sampling voltage VIN delivered by the humidity sensor sampling circuit 001. Negate.

Referring to FIG. 5, the A/D conversion pre-output circuit 006 includes a voltage dividing circuit and an LM358 op amp follower; the A/D conversion pre-output circuit 006 mainly collects an emitter voltage of an emitter of the driving output circuit 003. VO voltage signal, and then use LM358 op amp follower to take out the voltage signal, so that the microcontroller system to operate and control.

The A/D conversion pre-output circuit 006 collects the voltage signal of the emitter voltage VO of the emitter of the driving output circuit 003 via the R27 resistor and the R28 resistor divider (the voltage range of the sampling by the single-chip system is 0-3.3V). Then, the voltage signal is taken out by the LM358 op amp follower U5B, so that the MCU system can perform calculation and control.

Referring to FIG. 6, the single chip microcomputer system 005 includes an STM32 single chip microcomputer, and the model of the STM32 single chip microcomputer is preferably STM32F103R8; the STM32 single chip device is cost-effective, with A/D, communication, I/O, timing counter, watchdog, etc. Interface, strong computing power.

Referring to FIG. 7, the human-machine dialog unit 007 includes a debug button and an LED indicator module; the debug button specifically uses two independent buttons; the LED indicator module is an LED light D1; the two independent The type buttons are respectively a measurement button KEY1 and a self-correction button KEY2; the measurement button KEY1 and the self-correction button KEY2 are preferably a 4-pin micro switch, further preferably a 4-pin micro switch 6*6*5; The KEY1 is connected to the PC7 pin of the STM32 microcontroller, and the self-correction button KEY2 is connected to the PC8 pin of the STM32 microcontroller.

The interface module 008 is used for interface expansion and is optional according to user requirements; specifically, the RS232 interface is used for RS-232C communication, and the Max3232 chip of the US company is further preferably used.

The invention is mainly for the problem that the manual adjustment circuit parameters are arbitrarily large and the precision is inconsistent and inconsistent in the production of the intelligent humidity sensor, and the intelligent closed loop is formed by the A/D conversion pre-input circuit 004 and the A/D conversion pre-output circuit 006. The control system adopts the intelligent closed-loop control system, self-adjusting the circuit parameters through the single-chip microcomputer system, and can increase the interface module 008 as the communication module, effectively improving the production process and widening the application range of the sensor; using the single-chip microcomputer system and the digital potentiometer Realize the adjustment of the zero point and magnification of the smart sensor.

The invention adds 008 as an interface module, which can realize the function of the digital sensor. As long as the module such as wifi or radio frequency is added, the wireless sensor network can be formed, which expands the application range of the sensor; conforms to the trend of intelligent transformation of the traditional sensor today, Promote value.

The invention can realize the automatic adjustment of the sensor, and the utility model can realize the adjustment of the transmitter amplification and the zero point control circuit parameter by using the single-chip computer system calculation by simple manual operation, and the specific working method of the intelligent humidity sensor of the invention is as shown in the table. 1:

Table 1 Intelligent humidity sensor W1, W2 adjustment and x, y relationship process

The specific working method of the intelligent humidity sensor of the present invention is as follows:

Select a transmitter with a relative humidity of 0% to 100% corresponding to 0V to 5V; during commissioning, generally select a relatively low humidity (relative humidity of 30%) and a relative high point (relative humidity of 85%) as reference points. Then, the theoretical corresponding output voltage of the intelligent humidity sensor with adaptive function should be 1.5V, 4.25V; the relatively low point and the relatively high point, the present invention is 30% humidity and 85% humidity respectively, and the whole process of debugging as follows:

1) By simulating the relatively low point and relatively high point humidity environment, the amplification control circuit 002 reads the voltage output by the humidity sensor sampling circuit 001 at the relatively low and relatively high humidity points as the corresponding sampling voltage VIN, relative low point and relative The sampling voltage VIN corresponding to the high point is x1 and x2, respectively. The specific method is as follows: the polymer humidity sensor RH is measured at a relative humidity of 30% under the condition of a relative humidity of 30%, and the button KEY1 is measured by one time in a period of 3 seconds. Corresponding sampling voltage x1, LED indicator flashes; polymer humidity sensor RH in the relative humidity of 85%, 3 seconds of continuous measurement button 2 KEY1 measured relative humidity high point corresponding sampling voltage x2 , the LED indicator flashes twice;

2) As shown in Fig. 3, calculate the theoretical resistance of the W1 programmable potentiometer and the W2 programmable potentiometer, and the corresponding relationship between the output voltage of the amplification control circuit 002 and the input sampling voltage is:

VO=-(R4+R _W2 )×(VIN+12×(R2+R _W1 )/(R2+R3+RM))/R9(1)

Among them, VIN represents the sampling voltage, VO represents the output voltage, RM is the maximum resistance of the digital potentiometer x9110 100K, the resistance of the R9 resistor and the R11 resistor are equal, and the resistance of the W1 programmable potentiometer in the amplification control circuit 002 is R _W1 The resistance of the W2 programmable potentiometer is R _W2 ;

Input sampling voltage x1, sampling voltage x2, the corresponding output voltage theoretical value is 1.5V, 4.25V, substituted into (1), can get the equation:

-(R4+R _W2 )×(x1+12×(R2+R _W1 )/(R2+R3+RM))/R9=1.5; (2)

-(R4+R _W2 )×(x2+12×(R2+R _W1 )/(R2+R3+RM))/R9=4.25;(3)

Solved by equations (2) and (3):

R _W2 = R9 × 2.75 / (x1-x2) - R4; (4)

Substituting (4) into (2) can find R _W1 ;

The single chip system 005 calculates the values of the resistance value R _W1 and the resistance value R _W2 according to the above formula, and adjusts the programmable potentiometer W1 and the programmable potentiometer W2;

3) Self-calibration: Because each humidity sensor and circuit will have differences, the actual relative low and relative high output voltages may not be exactly 1.5V and 4.25V, so the error calculation should be compared with the actual value. Methods as below:

Repeat step 1), press the measurement button KEY1 to change to press the self-correction button KEY2;

By simulating the relatively low-point and relatively high-point humidity environment, the amplification control circuit 002 reads the voltage outputted by the humidity sensor sampling circuit 001 at the relatively low and relatively high humidity levels as the corresponding sampling voltage VIN x1, x2, respectively, and the amplification control The signal output end of the circuit 002 outputs a corresponding driving output voltage VO of y1, y2;

The specific method is as follows: the polymer humidity sensor RH is pressed at a relative humidity of 30%, and the self-calibration button KEY2 is pressed 1 time in a period of 3 seconds, and the sampling voltage x1 corresponding to the low relative humidity is measured, and the LED indicator flashes. The output voltage y1 of the signal output end of the drive output circuit 003 is measured; the relative humidity of the polymer humidity sensor RH is 85% in the period of 3 seconds, and the relative humidity is measured according to the self-correction button KEY2. The sampling voltage x2, the LED indicator flashes twice, and the output voltage y2 of the signal output end of the driving output circuit 003 is measured;

Humidity low point error: Δ1 = y1-1.5;

Humidity high point error: Δ2 = y2-4.25;

The error is the absolute value of Δ1 and Δ2;

4) Calculate the values of R _W1 and R _W2 based on actual values:

Substituting the corresponding output voltage into equations (2) and (3), the theoretical value of the output voltage is 1.5V, 4.25V becomes the actual value y1, y2;

-(R4+RW2)×(x1+12×(R2+RW1)/(R2+R3+RM))/R9=y1;(5)

-(R4+RW2)×(x2+12×(R2+RW1)/(R2+R3+RM))/R9=y2;(6)

According to the method of step 2), the values of the resistance value R _W1 and the resistance value R _W2 are calculated again, and the W1 programmable potentiometer and the W2 programmable potentiometer are adjusted;

5) Repeat step 3) for the second self-calibration to obtain the drive output voltages y1' and y2'

Humidity low point error: Δ1' = y1'-1.5;

Humidity high point error: Δ2' = y2' - 4.25;

The new error is calculated as the absolute value of Δ1' and Δ2';

The output voltages y1' and y2' are driven again according to the actual values, and the values of the resistance values R _W1 and the resistance values R _W2 are calculated:

Finally, the value of the resistance value R _W1 and the resistance value R _W2 takes the value of the second time when the second error is relatively small.

Example

An intelligent humidity sensor having a humidity sensor sampling circuit 001, an amplification control circuit 002, an A/D conversion pre-input circuit 004, a single-chip system 005, an A/D conversion pre-output circuit 006, a human-machine dialogue unit 007, The interface module 008 is composed; wherein the first signal output end of the humidity sensor sampling circuit 001 is connected to the first signal input end of the amplification control circuit 002, the second signal output end of the humidity sensor sampling circuit 001 and the A/D conversion pre-input The signal input end of the circuit 004 is connected, and the signal output end of the A/D conversion pre-input circuit 004 is connected to the first signal input end of the single chip system 005, and the signal of the second signal input end of the single chip system 005 and the human-machine dialogue unit 007 The output end is connected, the third signal input end of the single chip system 005 is connected with the signal output end of the A/D conversion pre-output circuit 006, and the first signal input and output end of the single chip system 005 is connected to the signal input and output end of the amplification control circuit 002. The signal output end of the amplification control circuit 002 is connected to the signal input end of the A/D conversion pre-output circuit 006; the intelligent humidity sensor is further Interface module 008 includes, a signal input and output interface module SCM system 008 and the second signal input connected to output terminal 005.

The humidity sensor sampling mode 001 circuit is shown in Figure 2. A typical RC bridge oscillator circuit is formed by R20, C31, C32, R22, R23, R24 and the operational amplifier U2A, and a sine wave with a frequency of 1 kHz and an amplitude of 1 V is generated as the humidity. The sensor is supplied with power. In order to reduce the influence of the rear circuit on the front circuit, the first-stage operational amplifier U2B is added to function as an impedance isolation; C33 is a DC-blocking capacitor; the humidity sensor is divided by RT and W3, and RT is a temperature compensation resistor. AC amplification by U2C, D4 is half-wave rectification, and finally R5 and C30 are 1st-order filtering, turning AC into DC; VIN is input A/D conversion module 004, and input voltage of transmitter amplification and zero control circuit 002 .

The amplification control circuit 002 is as shown in FIG. 3. The amplification control circuit 002 includes a transmitter amplifying circuit, a zero point control circuit, and a driving output circuit 003. The transmitter amplifying circuit and the zero point control circuit include two parts, and the upper part is an amplifying circuit. The negative feedback op amp amplifier circuit U2D is adopted, W2 and R4 are feedback resistors for adjusting the amplification factor, and the R4 is fixed to improve the adjustment accuracy of the digital potentiometer. The amplification circuit is mainly for satisfying the output maximum of the intelligent humidity sensor to reach 5V; The half is a zeroing circuit. It is a typical op amp summing circuit. The resistance values of R9 and R11 are the same. One end is the sampling voltage of the humidity sensor, the output voltage of the 001 module is VIN, and the other end is the digital potentiometer and two fixed. The partial pressure of the resistors (R2, R3, W1), theoretically, when the relative humidity is 0%, the voltage values of VT and VIN are the same, and the direction is opposite. In this case, when the relative humidity is 0%, the output of the intelligent humidity sensor can be Zero.

The drive output circuit 003 uses a triode emitter follower Q1 output to increase drive capability and impedance isolation.

In order to realize a self-adjusting closed-loop control system, the A/D conversion pre-input circuit 004 adopts an LM358 op amp follower, and mainly collects a voltage signal transmitted by the humidity sensor sampling circuit 001 at the input end; before the A/D conversion The output circuit 006 includes a voltage dividing circuit and an LM358 op amp follower; the A/D conversion pre-output circuit 006 mainly collects the voltage signal of the emitter voltage VO of the emitter of the output circuit 003, and then uses the LM358 op amp follower. The voltage signal is taken out for the operation and control of the microcontroller system.

The single chip system 005 adopts STM32 single chip STM32F103R8 (Fig. 6). The chip is cost-effective, with A/D, communication, I/O, timing counter and watchdog interface, and has strong computing power; pin RXD1 TXD1 is a serial interface and is connected to the RS232 interface. The pins ADC0 and ADC1 are respectively connected to the AD conversion pre-circuit module 004 and the AD conversion pre-circuit module 006 for input and output voltage signal acquisition, and the pins SO, SI SCK, CSW1, and CSW2 are used to connect the amplification control circuit 002 for adjusting the parameters of the circuit, and the remaining JNTRSR, JTDI, SWDIO, SWCLK, and JTDO are JTAG socket pins.

The human-machine dialog unit 007 includes a debug button and an LED indicator module; the debug button is specifically connected to the single-chip pins PC7 and PC8 by two independent buttons; the LED indicator module is an LED light D1; The two independent keys are the measurement key KEY1 and the self-correction key KEY2; the measurement key KEY1 and the self-correction key KEY2 are preferably 4-pin micro-switches, further preferably 4-pin micro-switches 6*6*5.

The RS232 interface module 008 is used for interface expansion and is optional according to user requirements; specifically, the RS232 interface is used for RS-232C communication, and the Max3232 chip U4 of the US-based company is further preferably used; the RS232 interface module 008 mainly functions to convert the TTL level. Into the RS-232C level, J2 is the output plug, the other five capacitors are peripheral circuits, specifically refer to the datasheet of the max3232 chip, the main function can easily access the wifi module, 4G communication module and RF module, etc., to expand the intelligent humidity sensor Application range.

Claims

The intelligent humidity sensor is characterized by comprising a humidity sensor sampling circuit (001), an amplification control circuit (002), an A/D conversion pre-input circuit (004), a single-chip system (005), and an A/D conversion pre-output circuit ( 006) a human-machine dialog unit (007); wherein the first signal output end of the humidity sensor sampling circuit (001) is connected to the first signal input end of the amplification control circuit (002), and the humidity sensor sampling circuit (001) is The second signal output end is connected to the signal input end of the A/D conversion pre-input circuit (004), and the signal output end of the A/D conversion pre-input circuit (004) is connected to the first signal input end of the single chip system (005). The second signal input end of the single chip system (005) is connected to the signal output end of the human machine dialogue unit (007), the third signal input end of the single chip system (005) and the A/D conversion pre-output circuit (006) The signal output end is connected, the first signal input and output end of the single chip system (005) is connected with the signal input and output end of the amplification control circuit (002), and the signal output end of the amplification control circuit (002) and the A/D conversion pre-output circuit are connected. The signal inputs of (006) are connected.
The intelligent humidity sensor according to claim 1, wherein the intelligent humidity sensor further comprises an interface module (008), a signal input and output end of the interface module (008) and a second signal input and output end of the single chip system (005). Connected.
The intelligent humidity sensor according to claim 1 or 2, wherein the humidity sensor sampling circuit (001) includes a polymer humidity sensor (RH), and the polymer humidity sensor (RH) is a polymer resistor type. The humidity sensor is powered by an RC bridge oscillating circuit, and the RC bridge oscillating circuit generates a sine wave having a frequency of 1 kHz and an amplitude of 1 V to supply power to the polymer humidity sensor, and the RC bridge oscillating circuit is high. The molecular humidity sensor (RH), the temperature compensation resistor RT, the W3 resistor, and the power supply form a voltage dividing circuit. The voltage division is AC amplified by another stage of the operational amplifier U2C, and the diode D4 acts as a half-wave rectification. Finally, the R5 resistor and the C30 capacitor are The first-order filtering converts the alternating current into a direct current voltage VIN; the RC bridge type oscillation circuit includes an R20 resistor, a C31 capacitor, a C32 capacitor, an R22 resistor, an R23 resistor, and an operational amplifier U2A.
The intelligent humidity sensor according to claim 1 or 2, wherein said amplification control circuit (002) comprises a transmitter amplifying circuit, a zero point control circuit, and a driving output circuit (003); said transmitter amplifying circuit adopts Negative feedback op amp amplifier circuit, in order to improve the digital potentiometer to adjust the resistance resolution of a certain section, W2 programmable potentiometer and R4 resistor in series, constitute a feedback resistor, used to adjust the amplification factor, the transmitter amplifier circuit is mainly to meet The output of the intelligent humidity sensor has a maximum value of 5V; the zero point control circuit uses an operational amplifier summing circuit, and the operational amplifier summation circuit includes one positive polarity circuit and one negative polarity circuit; the negative polarity circuit samples the humidity sensor The sampling voltage (VIN) outputted by the first signal output terminal of the circuit (001) is connected to the negative terminal of the negative feedback operational amplifier amplifier circuit (U2D) through the R9 resistor; the positive polarity circuit includes a 12V voltage terminal, a W1 programmable potentiometer, R2 resistor, R3 resistor, analog ground, 12V voltage terminal is connected with external 12V power supply, W1 programmable potentiometer center tap is also connected to negative feedback op amp amplifier circuit (U2D) through R11 resistor As long as the resistance of the R9 resistor is equal to the resistance of the R11 resistor, the input voltage of the negative feedback op amp amplifier circuit (U2D) is the sum of the two. The function of the W1 programmable potentiometer is to adjust the voltage of the drive output circuit (003). Low point.
The intelligent humidity sensor according to claim 4, wherein the W1 programmable potentiometer and the W2 programmable potentiometer each use a digital potentiometer x9110.
The intelligent humidity sensor of claim 4 wherein said drive output circuit (003) employs a triode emitter follower output.
The intelligent humidity sensor according to claim 1 or 2, wherein said A/D conversion pre-input circuit (004) uses an LM358 op amp (U5A) for inverting amplification, and if R29 and R30 have equal resistance values, Then the function of the circuit reverses the sampling voltage (VIN) delivered by the humidity sensor sampling circuit (001); the A/D conversion pre-output circuit (006) includes a voltage dividing circuit and an LM358 op amp follower (U5B); The A/D conversion pre-output circuit (006) collects the voltage signal of the emitter voltage (VO) of the emitter of the drive output circuit (003) via the R27 resistor, the R28 resistor divider, and then passes the LM358 op amp follower (U5B). Take out the voltage signal for the microcontroller system to perform calculations and control.
The intelligent humidity sensor according to claim 1 or 2, wherein said single chip microcomputer system (005) comprises an STM32 single chip microcomputer; said human machine dialogue unit (007) comprises a debug button and an LED indicator module; said LED indicator light The module is an LED lamp; the two independent buttons are a measurement button (KEY1) and a self-correction button (KEY2); the measurement button (KEY1) and the self-correction button (KEY2) are 4-pin micro-switches; The measurement button (KEY1) is connected to the PC7 pin of the STM32 microcontroller, and the self-calibration button (KEY2) is connected to the PC8 pin of the STM32 microcontroller.
The intelligent humidity sensor according to claim 2, wherein said interface module 008 performs RS-232C communication using an RS232 interface.
The intelligent humidity sensor according to claim 1, wherein the specific working method is as follows:

Select a transmitter with a relative humidity of 0% to 100% corresponding to 0V to 5V; in debugging, generally select the relative low point of the humidity and the relative high point as the reference point, then the intelligent humidity sensor with adaptive function is theoretically The corresponding output voltage should be 1.5V, 4.25V; the relative low point and relative high point are humidity 30% and humidity 85% respectively. The whole process of debugging is as follows:

1) By simulating the relatively low and relatively high humidity environment, the amplification control circuit (002) reads the voltage output by the humidity sensor sampling circuit (001) at the relatively low and relatively high humidity levels as the corresponding sampling voltage (VIN). The sampling voltages (VIN) corresponding to the relatively low points and the relatively high points are respectively x1 and x2; the specific method is: the polymer humidity sensor (RH) is pressed at a relative humidity of 30%, and is pressed for 1 time in a period of 3 seconds. The measurement button (KEY1) measures the sampling voltage x1 corresponding to the low relative humidity, and the LED indicator flashes; the polymer humidity sensor (RH) continuously presses 2 times in the 3 second period under the condition of relative humidity of 85%. The measurement button (KEY1) measures the sampling voltage x2 corresponding to the high relative humidity, and the LED indicator flashes twice;

2) Calculate the theoretical resistance of the W1 programmable potentiometer and W2 programmable potentiometer. The corresponding relationship between the output voltage of the amplification control circuit (002) and the input sampling voltage is:

VO=-(R4+R W2 )×(VIN+12×(R2+R W1 )/(R2+R3+RM))/R9 (1)

Where VIN represents the sampling voltage, VO represents the output voltage, RM is the maximum resistance of the digital potentiometer x9110 100K, the resistance of the R9 resistor and the R11 resistor are equal, and the resistance of the W1 programmable potentiometer in the amplification control circuit (002) The resistance of R W1 and W2 programmable potentiometer is R W2 ;

Input sampling voltage x1, sampling voltage x2, the corresponding output voltage theoretical value is 1.5V, 4.25V, substituted into (1), can get the equation:

-(R4+R W2 )×(x1+12×(R2+R W1 )/(R2+R3+RM))/R9=1.5; (2)

-(R4+R W2 )×(x2+12×(R2+R W1 )/(R2+R3+RM))/R9=4.25; (3)

Solved by equations (2) and (3):

R W2 =R9×2.75/(x1-x2)-R4; (4)

Substituting (4) into (2) can find R W1 ;

The single-chip microcomputer system (005) calculates the values of the resistance value R W1 and the resistance value R W2 according to the above formula, and adjusts the programmable potentiometer W1 and the programmable potentiometer W2;

3) Self-calibration: Because each humidity sensor and circuit will have differences, the actual relative low and relative high output voltages may not be exactly 1.5V and 4.25V, so the error calculation should be compared with the actual value. Methods as below:

Repeat step 1), press the measurement button (KEY1) to change to press the self-correction button (KEY2);

By simulating the relatively low and relatively high humidity environment, the amplification control circuit (002) reads the voltage output by the humidity sensor sampling circuit (001) at the relatively low and relatively high humidity levels as the corresponding sampling voltage (VIN), respectively. X1, x2, the output output voltage (VO) of the signal output end of the amplification control circuit (002) is y1, y2;

The specific method is as follows: the polymer humidity sensor (RH) is pressed at a relative humidity of 30%, and the self-calibration button (KEY2) is pressed for 1 time in a period of 3 seconds, and the sampling voltage x1 corresponding to the low relative humidity is measured. The indicator light flashes to measure the output voltage y1 of the signal output terminal of the drive output circuit (003); the polymer humidity sensor (RH) presses the self-correction button continuously for 2 seconds in the period of 3 seconds under the condition of relative humidity of 85%. (KEY2) measured the sampling voltage x2 corresponding to the high relative humidity, the LED indicator flashes twice, and the output voltage y2 of the signal output end of the driving output circuit (003) is measured;

Humidity low point error: Δ1 = y1-1.5;

Humidity high point error: Δ2 = y2-4.25;

The error is the absolute value of Δ1 and Δ2;

4) Calculate the values of R W1 and R W2 based on actual values:

Substituting the corresponding output voltage into equations (2) and (3), the theoretical value of the output voltage is 1.5V, 4.25V becomes the actual value y1, y2;

-(R4+R W2 )×(x1+12×(R2+R W1 )/(R2+R3+RM))/R9=y1; (5)

-(R4+R W2 )×(x2+12×(R2+R W1 )/(R2+R3+RM))/R9=y2; (6)

According to the method of step 2), the values of the resistance value R W1 and the resistance value R W2 are calculated again, and the W1 programmable potentiometer and the W2 programmable potentiometer are adjusted;

5) Repeat step 3) for the second self-calibration to obtain the drive output voltages y1' and y2'

Humidity low point error: Δ1' = y1'-1.5;

Humidity high point error: Δ2' = y2' - 4.25;

The new error is calculated as the absolute value of Δ1' and Δ2';

The output voltages y1' and y2' are driven again according to the actual values, and the values of the resistance values R W1 and the resistance values R W2 are calculated:

Finally, the value of the resistance value R W1 and the resistance value R W2 takes the value of the second time when the second error is relatively small.