CN110618238B - Self-adaptive driving circuit of gas sensor - Google Patents
Self-adaptive driving circuit of gas sensor Download PDFInfo
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- CN110618238B CN110618238B CN201910930494.6A CN201910930494A CN110618238B CN 110618238 B CN110618238 B CN 110618238B CN 201910930494 A CN201910930494 A CN 201910930494A CN 110618238 B CN110618238 B CN 110618238B
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- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0031—General constructional details of gas analysers, e.g. portable test equipment concerning the detector comprising two or more sensors, e.g. a sensor array
- G01N33/0032—General constructional details of gas analysers, e.g. portable test equipment concerning the detector comprising two or more sensors, e.g. a sensor array using two or more different physical functioning modes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
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Abstract
The invention belongs to the technical field of gas detection, and discloses a self-adaptive driving circuit and a self-adaptive driving method of a gas sensor and a handheld gas detector; the adaptive driving circuit of the gas sensor comprises: the device comprises a gas sensor socket, a first single-pole-three-throw analog switch, a second single-pole-three-throw analog switch, a third single-pole-three-throw analog switch, a first single-pole-two-throw analog switch, an adjustable voltage-controlled constant current source circuit, a second single-pole-two-throw analog switch, a voltage type digital-to-analog converter (DAC), an adjustable bias voltage generating circuit, a microcontroller, a band gap reference voltage generating circuit, a first integrated operational amplifier circuit, a second integrated operational amplifier circuit, a first resistor, a second resistor, a first in-phase amplifying circuit, a differential amplifying circuit, a second in-phase amplifying circuit, a third resistor, a fourth resistor and an analog-to-digital converter (ADC). The self-adaptive driving circuit of the gas sensor provided by the invention can realize efficient and convenient switching of different types of gas sensors on the same handheld gas detector.
Description
Technical Field
The invention relates to the technical field of gas detection, in particular to a self-adaptive driving circuit of a gas sensor.
Background
The gas sensors are various, and among them, the electrochemical type and contact combustion type gas sensors are most widely used in the detection of oxygen, toxic and harmful gases and combustible gases, and are the most mature, stable and reliable gas sensors in commercial use. The most common forms of electrochemical gas sensors and catalytic combustion are the 3-electrode type. For an electrochemical sensor, the 3 electrodes are a working electrode WE, an auxiliary electrode CE and a reference electrode RE, respectively. The catalytic combustion type sensor comprises a detection end S, a compensation end C and a bridge output end D. In practical application, different gases need to be detected in different occasions, and users need to frequently replace different types of portable detection instruments. This undoubtedly increases the cost of the user, and causes troubles in management and maintenance.
Disclosure of Invention
The invention provides a self-adaptive driving circuit of a gas sensor, which solves the technical problem that gas detectors in the prior art cannot simultaneously and compatibly drive different types of gas sensors.
In order to solve the above technical problem, the present invention provides an adaptive driving circuit for a gas sensor, including: the device comprises a gas sensor socket, a first single-pole-three-throw analog switch, a second single-pole-three-throw analog switch, a third single-pole-three-throw analog switch, a first single-pole-two-throw analog switch, an adjustable voltage-controlled constant current source circuit, a second single-pole-two-throw analog switch, a voltage type digital-to-analog converter (DAC), an adjustable bias voltage generating circuit, a microcontroller, a band-gap reference voltage generating circuit, a first integrated operational amplifier circuit, a second integrated operational amplifier circuit, a first resistor, a second resistor, a first in-phase amplifying circuit, a differential amplifying circuit, a second in-phase amplifying circuit, a third resistor, a fourth resistor and an analog-to-digital converter (ADC);
the gas sensor socket is provided with a first pin, a second pin and a third pin which are respectively connected with the COM pins of the first single-pole three-throw analog switch, the second single-pole three-throw analog switch and the third single-pole three-throw analog switch in a one-to-one correspondence manner, and the COM pin of the first single-pole double-throw analog switch is connected with the second pin of the gas sensor socket;
the control ends of the first single-pole three-throw analog switch, the second single-pole three-throw analog switch, the third single-pole three-throw analog switch and the first single-pole double-throw analog switch are connected with the microcontroller;
NO of the first single-pole-three-throw analog switch 0 The pin is connected with the analog-to-digital converter ADC and is grounded through a third resistor, and NO of the first single-pole three-throw analog switch 1 A pin is connected with the output end of the first integrated operational amplifier, and the NO2 pin of the first single-pole three-throw analog switch is grounded;
NO of the second single-pole triple-throw analog switch 0 The pin is connected with the output end of the adjustable voltage-controlled constant current source circuit, and NO of the second single-pole triple-throw analog switch 1 The pin is connected with the inverting input end of the second integrated operational amplifier through a first resistor, and NO of the second single-pole three-throw analog switch 2 The pin is connected with the first input end of the differential amplification circuit;
the third single knife threeNO of throw analog switch 0 A pin is connected with the analog-to-digital converter ADC and is grounded through a fourth resistor, and NO of the third single-pole three-throw analog switch 1 The pin is connected with the inverting input end of the first integrated operational amplifier, and NO of the third single-pole three-throw analog switch 2 The pin is connected with VDD;
NO of the first SPDT analog switch 0 Pin left blank, NO of the first single-pole double-throw analog switch 1 A pin is connected with a third pin of the gas sensor socket;
NO of the second single-pole double-throw analog switch 0 The pin is connected with the input end of the adjustable voltage-controlled constant current source circuit, and NO of the second single-pole double-throw analog switch 1 A pin is connected with the input end of the adjustable bias voltage generating circuit, a COM pin of the second single-pole double-throw analog switch is connected with the output end of the voltage type digital-to-analog converter DAC, and a control end of the second single-pole double-throw analog switch is connected with the microcontroller;
the DAC input end of the voltage type digital-to-analog converter is connected with the microcontroller;
the output end of the adjustable bias voltage generating circuit is connected with the non-inverting input end of the first integrated operational amplifier;
the input end of the band-gap reference voltage generating circuit is connected with the microcontroller, and the output end of the band-gap reference voltage generating circuit is connected with the input end of the adjustable bias voltage generating circuit, the second input end of the differential amplifying circuit and the non-inverting input end of the second integrated operational amplifier;
the output end of the second integrated operational amplifier circuit is connected with the analog-to-digital converter (ADC) through the first in-phase amplifying circuit, and the output end of the second integrated operational amplifier circuit is connected with the inverting input end of the second integrated operational amplifier circuit through a second resistor;
the output end of the differential amplifying circuit is connected with the analog-to-digital converter ADC through the second in-phase amplifying circuit;
the analog-to-digital converter ADC is connected with the microcontroller.
Further, the adaptive driving circuit of the gas sensor further includes: IIC bus interface circuit;
the IIC bus interface circuit is connected with the microcontroller.
An adaptive driving method of a gas sensor is characterized in that the following operations are executed based on an adaptive driving circuit of the gas sensor:
identifying a sensor type of access to the gas sensor receptacle;
based on the acquired sensor type, switching the drive signal applied to the gas sensor socket and acquiring an output:
wherein the sensor types include: catalytic combustion type sensors and electrochemical type sensors.
Further, the identifying a sensor type of access to the gas sensor receptacle comprises:
NO of the first single-pole-three-throw analog switch 0 Pin on, NO of the second single-pole triple-throw analog switch 0 Pin on, NO of the third SPDT analog switch 0 Pin on, NO of the first SPDT analog switch 0 The pin is conducted, the adjustable voltage-controlled constant current source circuit generates a current signal and outputs the current signal to the NO of the second single-pole three-throw analog switch 0 A pin;
the microcontroller controls an ADC to periodically collect NO of the first single-pole-three-throw analog switch by a set period 0 Pin and NO of the third single-pole-three-throw analog switch 0 Judging the type of the sensor according to the voltage signal value of the pin and the acquired voltage signal value;
wherein NO of the first single-pole-three-throw analog switch 0 Pin and NO of the third single-pole-three-throw analog switch 0 The voltage signal values of the pins are all larger than 0, and the gas sensor is a catalytic combustion type sensor;
NO of the first single-pole triple-throw analog switch 0 Pin and NO of the third single-pole-three-throw analog switch 0 And the voltage signal values of the pins are equal to 0, so that the gas sensor is an electrochemical sensor.
Further, in the case where the gas sensor is a catalytic combustion type sensor, the switching the drive signal applied to the gas sensor socket based on the acquired sensor type includes:
the microcontroller controls NO of the first single-pole three-throw analog switch 2 Pin on, NO of the second single-pole triple-throw analog switch 2 Pin on, NO of the third SPDT analog switch 2 The pin is turned on.
Further, in the case where the gas sensor is an electrochemical-type sensor, the switching the drive signal applied to the gas sensor socket based on the acquired sensor type includes:
the microcontroller controls NO of the first single-pole three-throw analog switch 1 Pin on, NO of the second single-pole triple-throw analog switch 1 Pin on, NO of the third SPDT analog switch 1 The pin is turned on.
A hand-held gas detector, comprising: the gas sensor comprises a shell, a lining piece, a lining locking piece, a gas sensor socket, a gas sensor, a sensor protection cover and an adaptive driving circuit of the gas sensor;
the lining part is fixed in the shell, and the lining locking part is fixed on the shell and tightly presses the lining part;
gas sensor's self-adaptation drive circuit fixes on the interior backing member, the gas sensor socket with gas sensor's self-adaptation drive circuit links to each other, just the gas sensor socket is fixed in the inside lining retaining member, gas sensor inlays and inserts on the gas sensor socket, sensor safety cover detachably fixes on the inside lining retaining member.
Furthermore, a first sealing ring is arranged between the gas sensor and the sensor protection cover, and a second sealing ring is arranged between the gas sensor and the lining locking piece.
Further, a buzzer is fixed in the lining piece and connected with the self-adaptive driving circuit of the gas sensor;
a display screen is fixed in the lining piece and connected with a self-adaptive driving circuit of the gas sensor;
the shell is provided with a display window, and the display window is correspondingly arranged above the display screen;
and an LED alarm is fixed in the inner lining piece and connected with the self-adaptive driving circuit of the gas sensor.
Further, the microcontroller is connected with a wireless communication module and a GNSS module.
One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:
the self-adaptive driving circuit of the gas sensor provided by the embodiment of the application can autonomously identify the type of the connected gas sensor, specifically configure the parameters of the signal conditioning circuit and output the corresponding detection result. The portable detection instrument based on the technology can allow a user to flexibly replace different types of gas detection sensors on one host, so that the portable detection instrument realizes multiple purposes, greatly reduces the cost of the user, simplifies the use training of the user, and improves the management and maintenance efficiency of the instrument.
Drawings
Fig. 1 is a schematic structural diagram of an adaptive driving circuit of a gas sensor according to an embodiment of the present invention;
fig. 2 is a schematic circuit diagram of a power supply according to an embodiment of the invention;
FIG. 3 is a schematic diagram of a microcontroller and peripheral circuits according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a gas sensor socket and an analog switch according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of an electrochemical sensor signal processing circuit according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a signal processing circuit of a catalytic combustion sensor according to an embodiment of the present invention;
fig. 7 is a schematic circuit diagram of a second spdt analog switch according to an embodiment of the present invention;
fig. 8 is a schematic diagram of a circuit structure of an adjustable voltage-controlled constant current source according to an embodiment of the present invention;
fig. 9 is a schematic structural diagram of an adjustable bias voltage circuit according to an embodiment of the present invention;
FIG. 10 is a schematic diagram of an overall structure of a hand-held gas detector according to an embodiment of the present invention;
fig. 11 is a detailed structural schematic diagram of the handheld gas detector provided in the embodiment of the present invention.
Detailed Description
The embodiment of the application provides a self-adaptation drive circuit of gas sensor, solves the technical problem that gas detectors in the prior art can not be compatible simultaneously to drive gas sensors of different types.
In order to better understand the technical solutions, the technical solutions will be described in detail below with reference to the drawings and the specific embodiments of the specification, and it should be understood that the embodiments and specific features of the embodiments of the present invention are detailed descriptions of the technical solutions of the present application, and are not limitations of the technical solutions of the present application, and the technical features of the embodiments and examples of the present application may be combined with each other without conflict.
Referring to fig. 1, an adaptive driving circuit of a gas sensor includes: the gas sensor comprises a gas sensor socket 1, a first single-pole-three-throw analog switch 22, a second single-pole-three-throw analog switch 23, a third single-pole-three-throw analog switch 21, a first single-pole-two-throw analog switch 24, an adjustable voltage-controlled constant current source circuit 3, a second single-pole-two-throw analog switch 4, a voltage-type digital-to-analog converter DAC5, an adjustable bias voltage generating circuit 7, a microcontroller 8, a band-gap reference voltage generating circuit 9, a first integrated operational amplifier circuit 10, a second integrated operational amplifier circuit 11, a first resistor 12, a second resistor 13, a first in-phase amplifying circuit 14, a differential amplifying circuit 15, a second in-phase amplifying circuit 16, a third resistor 19, a fourth resistor 18 and an analog-to-digital converter ADC6.
The gas sensor socket 1 is provided with a first pin CE/C, a second pin WE/S and a third pin RE/D, which are respectively connected to the COM pins of the first single-pole-triple-throw analog switch 22, the second single-pole-triple-throw analog switch 23 and the third single-pole-triple-throw analog switch 21 in a one-to-one correspondence manner, and the COM pin of the first single-pole-double-throw analog switch 24 is connected to the second pin WE/S of the gas sensor socket 1.
The control ends of the first single-pole-three-throw analog switch 22, the second single-pole-three-throw analog switch 23, the third single-pole-three-throw analog switch 21 and the first single-pole-two-throw analog switch 24 are connected with the microcontroller 8, so that the combined control of the analog switches can be realized under the unified coordination of the microcontroller, the switching and the control of each circuit can be realized, and the function circuit specific configuration of various types of sensors can be realized; as in the present embodiment, the configuration of the respective functional circuits can be realized for the electrochemical-type sensor and the catalytic combustion-type sensor.
NO of the first SPDT analog switch 22 0 Pin 2-1 is connected to the ADC6 and to ground via a third resistor 19, NO of the first spdt analog switch 22 1 Pin 2-2 is connected to the output of the first integrated operational amplifier 10, NO of the first spdt analog switch 22 2 Pin 2-3 is grounded.
NO of the second single-pole-three-throw analog switch 23 0 A pin 3-1 is connected with the output end of the adjustable voltage-controlled constant current source circuit 3, and NO of the second single-pole triple-throw analog switch 23 1 Pin 3-2 is connected to the inverting input terminal of the second integrated operational amplifier 11 through a first resistor 12, and NO of the second single-pole triple-throw analog switch 23 2 Pin 3-3 is connected to a first input of the differential amplifier circuit 15.
NO of the third single-pole-three-throw analog switch 21 0 Pin 1-1 is connected to the ADC6 and is connected to ground via a fourth resistor 18, NO of the third spdt analog switch 21 1 Pin 1-2 and the first integrated operational amplifier10, NO of the third single-pole-triple-throw analog switch 21 2 Pins 1-3 are connected to VDD.
NO of the first SPDT analog switch 24 0 Pin 4-1 left blank, NO of the first single pole double throw analog switch 24 1 Pin 4-2 is connected to a third pin RE/D of the gas sensor socket 1.
NO of the second SPDT 4 0 The pin is connected with the input end of the adjustable voltage-controlled constant current source circuit 3, and NO of the second single-pole double-throw analog switch 4 1 A pin is connected with an input end of the adjustable bias voltage generating circuit 7, a COM pin of the second single-pole double-throw analog switch 4 is connected with an output end of the voltage-type digital-to-analog converter DAC5, and a control end of the second single-pole double-throw analog switch 4 is connected with the microcontroller 8, so that the microcontroller 8 controls the second single-pole double-throw analog switch 4 to select the adjustable voltage-controlled constant current source circuit 3 or the adjustable bias voltage generating circuit 7 to be switched on, thereby realizing type detection and subsequent gas detection of the accessed sensor; and in cooperation, the input end of the voltage type digital-to-analog converter DAC5 is connected with the microcontroller 8 to realize the state monitoring of the second single-pole double-throw analog switch 4.
The output terminal of the adjustable bias voltage generating circuit 7 is connected to the non-inverting input terminal of the first integrated operational amplifier 10.
The input end of the band-gap reference voltage generating circuit 9 is connected with the microcontroller 8, and the output end of the band-gap reference voltage generating circuit 9 is connected with the input end of the adjustable bias voltage generating circuit 7, the second input end of the differential amplifying circuit 15 and the non-inverting input end of the second integrated operational amplifier 11.
The output end of the second integrated operational amplifier circuit 11 is connected to the analog-to-digital converter ADC6 through the first non-inverting amplifier circuit 14, and the output end of the second integrated operational amplifier circuit 11 is connected to the inverting input end of the second integrated operational amplifier circuit 11 through the second resistor 13; the output end of the differential amplifying circuit 15 is connected with the analog-to-digital converter ADC6 through the second in-phase amplifying circuit 16; the analog-to-digital converter ADC6 is connected to the microcontroller 8.
Further, in order to realize external information transmission, the adaptive driving circuit of the gas sensor further comprises: an IIC bus interface circuit 17; the IIC bus interface circuit 17 is connected to the microcontroller 8.
In general, a status circuit 20 can also be connected to the microcontroller 8 in order to indicate the operating state.
The present embodiment further provides a method for realizing different types of gas detection by replacing different types of gas sensors on a handheld gas detector, based on the above circuit structure; the description will be made by taking a catalytic combustion type sensor and an electrochemical type sensor as examples.
An adaptive driving method of a gas sensor is based on an adaptive driving circuit of the gas sensor, and comprises the following operations:
the type of sensor that is accessed to the gas sensor receptacle is identified, i.e., after the gas sensor is accessed, it is identified in real time as being either a catalytic combustion type sensor or an electrochemical type sensor.
Switching a drive signal applied to the gas sensor socket and collecting an output based on the acquired sensor type.
As will be described in detail below.
The identifying a sensor type accessed to the gas sensor receptacle comprises:
NO of the first single-pole-three-throw analog switch 22 0 Pin 2-1 is conducting, NO of the second single-pole three-throw analog switch 23 0 Pin 3-1 is turned on, and NO of the third single-pole triple-throw analog switch 21 0 Pin 1-1 is on, NO of the first spdt analog switch 24 0 The pin 4-1 is conducted, the adjustable voltage-controlled constant current source circuit 3 generates a current signal and outputs the current signal to the NO of the second single-pole three-throw analog switch 23 0 Pin 3-1, which then passes to the WE/S pin of the sensor socket 1;
the microcontroller 8 controls the analog-to-digital converter ADC6 periodically with a set periodCollecting NO of the first single-pole-three-throw analog switch 22 0 NO of pin 2-1 and the third SPDT analog switch 21 0 Judging the type of the sensor according to the voltage signal value of the pin 1-1 and the collected voltage signal value;
wherein NO of the first SPDT analog switch 22 0 NO of pin 2-1 and the third SPDT analog switch 21 0 The voltage signal values of the pins 1-1 are all larger than 0, and the gas sensor is a catalytic combustion type sensor;
NO of the first single-pole-three-throw analog switch 22 0 NO of pin 2-1 and the third SPDT analog switch 21 0 And the voltage signal values of the pins 1-1 are equal to 0, so that the gas sensor is an electrochemical sensor.
Typically, the current signal is a 10ua current signal, identifying a scan period of 200ms.
It should be noted that the functional driving circuits configured by the sensors are different due to different types of sensors, and the following description will be made with respect to the operating states of the driving circuits, so as to specifically describe the same.
In the case where the gas sensor is a catalytic combustion type sensor, circuitry automatically performs the following signal conditioning circuit parameter configuration process, the switching drive signals applied to the gas sensor socket based on the acquired sensor type comprising:
Correspondingly, the sensor signal is output through the WE/S terminal, processed by the differential amplifier circuit 15, enters the second non-inverting amplifier 16, and is further converted into a digital signal through the CH4 channel by the analog-to-digital converter 6, the digital signal is collected by the microcontroller 8, and finally output to an external system through the IIC bus interface circuit 17 in a specific digital protocol.
In the case where the gas sensor is an electrochemical-type sensor, circuitry automatically performs the following signal conditioning circuit parameter configuration process, the switching drive signals applied to the gas sensor socket based on the acquired sensor type comprising:
Correspondingly, the microcontroller 8 controls the second single-pole double-throw analog switch 4, so that the voltage type digital-to-analog converter DAC5 is connected to the adjustable bias voltage generating circuit 7; the bias voltage generated by the adjustable bias voltage generating circuit 7 is communicated with a reference electrode RE of the sensor through an inverting input end of the first integrated operational amplifier circuit 10, and a working electrode pin WE of the sensor is communicated with a transconductance amplifier formed by a first resistor 12, a second resistor 13 and a second integrated operational amplifier circuit 11; the signal passes through a first in-phase amplifying circuit 14 and enters a CH3 channel of the analog-to-digital converter ADC6.
The microcontroller 8 controls the acquisition analog-to-digital converter ADC6 to acquire the CH3 channel voltage so as to acquire the corresponding monitoring parameter.
According to the characteristics of the output signal, the microcontroller 8 controls the voltage type digital-to-analog converter DAC5 to generate different voltage outputs, and outputs the generated different bias voltages to the reference electrode RE of the sensor through the adjustable bias voltage generating circuit 7.
After being converted into digital signals, the digital signals are output to an external system through the IIC bus 17 by a digital protocol.
The present embodiment also provides a design example of a hardware circuit for a conventional functional structure of the gas detector.
Referring to fig. 2, the power circuit portion: the voltage-reducing circuit mainly reduces an external power supply into a system-operable power supply, and a reference source generating circuit provides reference voltage for other circuits.
CN1 is external power supply and communication interface, VIN is external power supply, and its input voltage range is: 3.7 to 5.5V, I2C _SDAand I2C _ SCL and the design are communicated with an external I2C bus. GND is the system ground reference.
U1 is LDO (XC 6504A301 MR-G), which forms a VDD step-down circuit with an output of 3.0V with peripheral devices L1, C2, C3 and C4 to supply power for a digital circuit of the system.
U2 is LDO (XC 6504A301 MR-G), and it and peripheral devices L2, C5, C6, C7 and C8 form an AVDD step-down circuit with an output of 3.0V, and supplies power to the analog circuit of the system.
U5 is reference voltage IC (LM 4041AIM 3X) which forms a stable 1.225V reference voltage with its peripheral devices L3, C14, R10, C15 for other circuits. R10, R11 act as current limiting to provide the appropriate operating current for U5.
Referring to fig. 3, the mcu and peripheral circuit portions: MCU and peripheral control circuit, status indication circuit and burn record mouth.
U3A is mainly the functional GPIO part of MCU (STM 32L072KBU 6), and U3B is mainly the power supply part of MCU.
ADC acquisition pin: 6 to 9 pins of the MCU are ADC acquisition channels.
Analog switch channel switching control: controlling the channels of analog switches U7, U9, U12 and U13 to switch by pins 1 to 2 of the MCU; the 14-pin and the 15-pin control the channel switching of the analog switch U6.
DAC output: and the 11 pin is a DAC output port of the MCU.
And (3) status indication: the pins 13 and 18 of the MCU are respectively connected with one LED, and the MCU plays a role in state indication.
Burning pins: pins 23 and 24 of the MCU are respectively a programming pin SWDIO and a programming pin SWCLK.
I2C communication: pins 27 and 28 of the MCU are communication pins I2C _ SDA and I2C _ SCL of I2C, respectively, and R4 and R5 are pull-up resistors for communication.
JFET control pin: the 18-pin JFET _ CTR is used to control Q1 so that the electrochemical-type sensor improves the turn-on settling time of the sensor.
A power supply port: pins 17, 24 and 32 of the MCU are VDD power supply ports of the MCU; 5 pins are AVDD power supply ports of the MCU.
Other pins: pin 3 of the MCU is a reset pin, and pin C10 is a decoupling capacitor; 30 pins are a programming mode selection pin, the default is a common programming mode, and the IO port is grounded through R9.
CN2 is a burning port of the MCU.
Referring to fig. 4, the sensor channel switching circuit portion: when the sensor is plugged into a corresponding interface, the circuit can judge whether the sensor is an electrochemical sensor or a catalytic combustion sensor by acquiring signals by the MCU, and then the MCU controls the analog switch to correctly guide the sensor signals into a corresponding channel and acquire the signals.
U10 is the general type gas sensor interface.
U7, U9, U12, U13 are single-pole triple-throw analog switches (TS 5A 339), and pins 5 (IN 1) and 6 (IN 2) control the conduction of pin 7 (COM) and pins 1 (NO 0), 2 (NO 1) and 3 (NO 2). 8 pins are power supply ports, and 4 pins are AGND.
C17, C23, C26, C28 are decoupling capacitances.
Referring to fig. 5, the electrochemical type sensor signal processing circuit part: and converting the electrochemical sensor signal into a voltage signal and amplifying the voltage signal so as to supply the MCU for ADC acquisition.
After the sensor channel switching circuit is partially switched, the original signals of the electrochemical sensor signals respectively reach CE, RE and WE networks.
In a three-electrode electrochemical sensor, the target gas diffuses into the sensor, passes through a membrane and then acts on the Working Electrode (WE). A constant potential circuit mainly composed of U8A detects the voltage of the Reference Electrode (RE) and supplies a current to the auxiliary electrode (CE) to keep the voltage between the RE terminal and the WE terminal constant. No current flows into or out of the RE terminal, so that the current flowing out of the CE terminal flows into the WE terminal, which is proportional to the target gas concentration. The current flowing through the WE terminal may be positive or negative depending on whether a reduction or oxidation reaction occurs in the sensor. Resistor R15 is typically very small so the voltage at the WE terminal is approximately equal to REF.
U8B converts the current signal of the electrochemical sensor into a voltage signal, the output voltage value of U8B is VREF + IWE.R17, and the voltage R14 and C19 are RC low-pass filters and then output to CH3 for MCU to carry out ADC acquisition.
Referring to fig. 6, the catalytic combustion type sensor signal processing circuit portion: and converting the catalytic combustion type sensor signal into a voltage signal and amplifying the voltage signal so as to supply the voltage signal to the MCU for ADC acquisition.
After being switched by the sensor channel switching circuit part, the original signal of the catalytic combustion type sensor reaches the U _ S network.
U14A (ADA 4528) and R24, R34, C28, C32 constitute a differential amplifier circuit, it carries on differential amplification to U _ S (catalytic combustion type sensor signal) and REF voltage, carry on the in-phase amplification again through U14B and R26, R33, R31, C33 constituent in-phase amplifier circuit, form CH4 network after the filter circuit formed by C30, R27, C31 finally, for MCU to carry on ADC acquisition signal.
Referring to fig. 7, the dac output channel switching circuit section: and the output channel of the DAC signal is switched to be used by different circuits.
U6 is a single-pole triple-throw analog switch (TS 5A 339), and 5 pins (IN 1) and 6 pins (IN 2) control the conduction of 7 pins (COM) and 1 pin (NO 0), 2 pins (NO 1) and 3 pins (NO 2). 8 pins are power supply ports, and 4 pins are AGND.
The function performed by the present circuit switches the DAC _ OUT signal output to DAC _ OUT0 or DAC _ OUT1.
Referring to fig. 8, the adjustable voltage-controlled constant current source circuit part: the constant current is regulated by the DAC output voltage.
U11A, R20, R22, R26 and Q2 form an adjustable voltage-controlled constant current source circuit, R20 and R22 are buffer protection resistors of U11A, and R16 is a power feedback resistor.
The principle is as follows: the current flowing through R16 from AVDD causes a voltage drop UR16 across R16, and the voltage at pin 3 of U11A is (AVDD-UR 16). When the current flowing through R16 increases, which causes UR16 to increase, (AVDD-UR 16) decreases, when (AVDD-UR 16) is lower than the voltage of DAC _ OUT0, pin 1 of U11A outputs low level to turn off the DS pole of Q2, DS of Q2 turns off causes UR16 to decrease, (AVDD-UR 16) increases, when (AVDD-UR 16) is higher than the voltage of DAC _ OUT0, pin 1 of U11A outputs high level, Q2 is turned on, and the current flowing through R16 increases. This is repeated until the voltage value of (AVDD-UR 16) is equal to the voltage value of DAC _ OUT0, and then a steady state is reached, at which time the current value of R16 is stabilized at I = (AVDD-DAC _ OUT 0)/R16.
Referring to fig. 9, the adjustable bias voltage circuit portion: and outputting a voltage signal in a required range through DAC voltage regulation.
The signals of +1.225V and DAC _ OUT1 reach the 5 pins of U11B through R23 and R25, respectively, and the voltage of the 5 pins of U11B is (+ 1.225V-DAC _ OUT 1) R25/(R23 + R25) + DAC _ OUT1. Generally, if R23= R25, the voltage is (+ 1.225V + DAC _OUT1)/2.
R30, R29 and U11B amplify the voltage at pin 5 of U11B in phase to form a suitable value REF for use by the chemical sensor signal processing circuit portion and the catalytic combustion sensor signal processing circuit portion.
Referring to fig. 10 and 11, the present embodiment further provides a hand-held gas detector including: outer shell 500, inner liner 400, inner liner lock 300, adaptive drive circuit 900 for the gas sensor, gas sensor 200, and sensor shield 100.
The lining member 400 is fixed in the outer case 500, and the lining locker 300 is fixed on the outer case 500 and presses the lining member 400; the adaptive driving circuit 900 of the gas sensor is fixed on the lining member 400, that is, the functional circuit part of the handheld gas detector is encapsulated and fixed in the housing 500 through the lining member 400 and the lining locking member 300, so as to form a stable sealing arrangement structure, thereby ensuring the stability and reliability of the function.
In this embodiment, a gas sensor socket 1 is disposed at one end of the housing 500, that is, at the end where the lining locking member 300 is located, and the gas sensor socket 1 is connected to the adaptive driving circuit 900 of the gas sensor, so as to form a fixing and electrical connection structure of the gas sensor 200, thereby being capable of realizing very convenient disassembly and assembly operations; that is, the operations of attaching and detaching the gas sensor 200 are performed outside the housing 500 and the lining member 400, and other functional structures of the measuring apparatus are not affected, so that the operation is very simple and efficient.
Especially, when different detection objects are detected by replacing different types of gas sensors 200 on site, the gas sensors can be replaced very conveniently, and the condition that a plurality of different types of handheld gas detectors need to be prepared when the gas sensors are used on site at present is not needed, so that different types of gas can be detected on one handheld gas detector by replacing different types of gas sensors 200, and the detection convenience is greatly improved.
For ease, the liner lock 300 is divided into two parts; a first portion fixed to the outer case 500 for locking the lining member 400, which may be generally provided in a screw coupling structure, to be screw-coupled to an inner wall of the outer case 500; the second part is provided with a containing groove cavity, the gas sensor socket 1 is fixed in the containing groove cavity of the second part of the lining locking member 300, and correspondingly, the gas sensor 200 is embedded in the gas sensor socket 1. The sensor protection cover 100 is detachably fixed to the inside locking member 300, and precisely, the inner wall of the sensor protection cover 100 is threaded and is threadedly coupled to the second portion of the inside locking member 300, so that it is possible to easily assemble and disassemble the sensor protection cover.
Further, in view of the high sealing requirement for gas detection, the first gasket 600 is provided between the gas sensor 200 and the sensor protection cap 100, and the second gasket 700 is provided between the gas sensor 200 and the liner lock 300.
Further, the adaptive driving circuit 900 of the gas sensor may be used as a main functional circuit of the gas detector, and the adaptive driving circuit of the gas sensor in the prior art is adopted, and only the connection end point of the gas sensor is externally connected with a gas sensor socket; generally, the adaptive driving circuit 900 for a gas sensor employs a printed circuit for convenience of fixing and integrated use.
Similarly, a power source 170 of the hand-held gas detector is fixed in the liner 400, and the power source 170 is connected to the printed circuit and is used as a power source for the hand-held gas detector to wirelessly operate.
Generally, in order to facilitate detection and reminding, a buzzer 110 is fixed in the lining member 400, and the buzzer 110 is connected with the adaptive driving circuit 900 of the gas sensor and used as a reminding device when the detection index exceeds a threshold value.
Further, a third sealing ring 120 is disposed between the bottom of the buzzer 110 and the bottom of the casing 500.
Similarly, a fourth sealing ring 150 is also arranged between the switch button 140 and the housing 500 of the handheld gas detector, so that the sealing performance is improved.
Similarly, a display screen 160 is fixed in the lining member 400, and the display screen 160 is connected with the adaptive driving circuit 900 of the gas sensor; and indicating the monitoring data in real time.
In order to maintain the sealing performance, the housing 500 is opened with a display window 130, and the display window 130 is correspondingly disposed above the display screen 160.
Further, an LED alarm 800 is fixed in the lining member 400, and the LED alarm 800 is connected to the adaptive driving circuit 900 of the gas sensor as an indicating element.
It should be noted that, in this embodiment, the inside lining locking member 300 is provided with a light guide ring, and the LED alarm 800 is disposed inside the light guide ring.
Specifically, the inner locking member 300 has a cylindrical structure with a hollow cavity therein, so that the electric connection structure can pass through the hollow cavity and the hollow cavity can be integrated with the accommodating groove. Meanwhile, a light guide ring made of a light-transmitting material is arranged on the cylindrical wall, so that light-transmitting indication is realized after the LED alarm 800 is inserted into the cylindrical cavity.
Generally, for a handheld gas detector with remote communication capability, in this embodiment, the adaptive driving circuit 900 of the gas sensor is connected to a wireless communication module and a GNSS module, so as to realize integral use.
One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:
the utility model provides a gaseous detector of hand-held type, for satisfying the demand of the convenient gaseous sensor who changes the gaseous detector of hand-held type, reform transform gas sensor's fixed knot structure on current gaseous detector of hand-held type's basis, adopt the self-adaptation drive circuit of the fixed gas sensor of interior backing member and fix interior backing member monolithic with interior car retaining member realize in the shell that the encapsulation of main part is fixed. The lining locking piece is provided with a structure for accommodating the gas sensor socket and the gas sensor, so that the gas sensor is embedded and replaced on the gas sensor socket outside the shell and the lining piece, convenient replacement operation is realized, the lining locking piece is particularly suitable for field replacement and use of different types of gas sensors on the same handheld gas detector, and convenient and efficient detection of different detection objects is met. Meanwhile, a matched gas sensor protection cover is arranged on the lining locking piece and is buckled above the gas sensor, so that protection is realized; meanwhile, the lock can be conveniently opened and locked, and is convenient to replace.
Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.
Claims (3)
1. A self-adaptive driving circuit of a gas sensor is suitable for field replacement and use of an electrochemical gas sensor and a catalytic combustion gas sensor on the same hand-held gas detector, and meets the requirements of convenient and efficient detection of different detection objects; it is characterized by comprising: the device comprises a gas sensor socket, a first single-pole-three-throw analog switch, a second single-pole-three-throw analog switch, a third single-pole-three-throw analog switch, a first single-pole-two-throw analog switch, an adjustable voltage-controlled constant current source circuit, a second single-pole-two-throw analog switch, a voltage type digital-to-analog converter (DAC), an adjustable bias voltage generating circuit, a microcontroller, a band-gap reference voltage generating circuit, a first integrated operational amplifier circuit, a second integrated operational amplifier circuit, a first resistor, a second resistor, a first in-phase amplifying circuit, a differential amplifying circuit, a second in-phase amplifying circuit, a third resistor, a fourth resistor and an analog-to-digital converter (ADC);
the gas sensor socket is provided with a first pin, a second pin and a third pin which are respectively connected with the COM pins of the first single-pole three-throw analog switch, the second single-pole three-throw analog switch and the third single-pole three-throw analog switch in a one-to-one correspondence manner, and the COM pin of the first single-pole double-throw analog switch is connected with the second pin of the gas sensor socket;
the control ends of the first single-pole three-throw analog switch, the second single-pole three-throw analog switch, the third single-pole three-throw analog switch and the first single-pole double-throw analog switch are connected with the microcontroller;
NO of the first single-pole-three-throw analog switch 0 The pin is connected with the analog-to-digital converter ADC and is grounded through a third resistor, and NO of the first single-pole three-throw analog switch 1 The pin is connected with the output end of the first integrated operational amplifier, and NO of the first single-pole three-throw analog switch 2 The pin is grounded;
NO of the second single-pole three-throw analog switch 0 The pin is connected with the output end of the adjustable voltage-controlled constant current source circuit, and NO of the second single-pole three-throw analog switch 1 The pin is connected with the inverting input end of the second integrated operational amplifier through a first resistor, and NO of the second single-pole three-throw analog switch 2 The pin is connected with the first input end of the differential amplification circuit;
NO of the third single-pole-three-throw analog switch 0 The pin is connected with the analog-to-digital converter ADC and is grounded through a fourth resistor, and NO of the third single-pole three-throw analog switch 1 The pin is connected with the inverting input end of the first integrated operational amplifier, and NO of the third single-pole three-throw analog switch 2 The pin is connected with VDD;
NO of the first single-pole double-throw analog switch 0 Pin blank, NO of the first SPDT analog switch 1 A pin is connected with a third pin of the gas sensor socket;
the second single-pole double-throw analog switchOff NO 0 The pin is connected with the input end of the adjustable voltage-controlled constant current source circuit, and NO of the second single-pole double-throw analog switch 1 A pin is connected with the input end of the adjustable bias voltage generating circuit, a COM pin of the second single-pole double-throw analog switch is connected with the output end of the voltage type digital-to-analog converter DAC, and a control end of the second single-pole double-throw analog switch is connected with the microcontroller;
the DAC input end of the voltage type digital-to-analog converter is connected with the microcontroller;
the output end of the adjustable bias voltage generating circuit is connected with the non-inverting input end of the first integrated operational amplifier;
the input end of the band-gap reference voltage generating circuit is connected with the microcontroller, and the output end of the band-gap reference voltage generating circuit is connected with the input end of the adjustable bias voltage generating circuit, the second input end of the differential amplifying circuit and the non-inverting input end of the second integrated operational amplifier;
the output end of the second integrated operational amplifier circuit is connected with the analog-to-digital converter (ADC) through the first in-phase amplifying circuit, and the output end of the second integrated operational amplifier circuit is connected with the inverting input end of the second integrated operational amplifier circuit through a second resistor;
the output end of the differential amplifying circuit is connected with the analog-to-digital converter (ADC) through the second in-phase amplifying circuit;
the analog-to-digital converter ADC is connected with the microcontroller;
the adaptive driving circuit of the gas sensor further includes: IIC bus interface circuit;
the IIC bus interface circuit is connected with the microcontroller.
2. An adaptive driving method of a gas sensor, characterized in that the following operations are performed based on the adaptive driving circuit of a gas sensor according to claim 1:
identifying a sensor type of access to the gas sensor socket;
based on the acquired sensor type, switching the driving signal applied to the gas sensor socket and acquiring an output:
wherein the sensor types include: catalytic combustion type sensors and electrochemical type sensors;
the identifying a sensor type accessed to the gas sensor receptacle comprises:
NO of the first single-pole-three-throw analog switch 0 Pin on, NO of the second single-pole triple-throw analog switch 0 Pin on, NO of the third SPDT analog switch 0 Pin on, NO of the first SPDT analog switch 0 The pin is conducted, the adjustable voltage-controlled constant current source circuit generates a current signal and outputs the current signal to the NO of the second single-pole three-throw analog switch 0 A pin;
the microcontroller controls the analog-to-digital converter ADC to periodically acquire NO of the first single-pole three-throw analog switch in a set period 0 Pin and NO of the third single-pole-three-throw analog switch 0 Judging the type of the sensor according to the voltage signal value of the pin and the acquired voltage signal value;
wherein NO of the first single-pole-three-throw analog switch 0 Pin and NO of the third SPDT analog switch 0 The voltage signal values of the pins are all larger than 0, and the gas sensor is a catalytic combustion type sensor;
NO of the first single-pole triple-throw analog switch 0 Pin and NO of the third SPDT analog switch 0 The voltage signal values of the pins are equal to 0, and the gas sensor is an electrochemical sensor;
in the case where the gas sensor is a catalytic combustion type sensor, the switching the drive signal applied to the gas sensor socket based on the acquired sensor type includes:
the microcontroller controls NO of the first single-pole three-throw analog switch 2 Pin on, NO of the second single-pole triple-throw analog switch 2 Pin on, NO of the third SPDT analog switch 2 Conducting the pins;
in the case where the gas sensor is an electrochemical-type sensor, the switching the drive signal applied to the gas sensor socket based on the acquired sensor type includes:
the microcontroller controls NO of the first single-pole three-throw analog switch 1 Pin on, NO of the second single-pole triple-throw analog switch 1 Pin on, NO of the third SPDT analog switch 1 The pin is turned on.
3. A hand-held gas detector, comprising: a housing, a liner lock, a gas sensor receptacle, a gas sensor, a sensor shield, and the adaptive drive circuit for a gas sensor of claim 1;
the lining part is fixed in the shell, and the lining locking part is fixed on the shell and tightly presses the lining part;
the self-adaptive driving circuit of the gas sensor is fixed on the lining piece, the gas sensor socket is connected with the self-adaptive driving circuit of the gas sensor, the gas sensor socket is fixed in the lining locking piece, the gas sensor is embedded in the gas sensor socket, and the sensor protection cover is detachably fixed on the lining locking piece;
a first sealing ring is arranged between the gas sensor and the sensor protection cover, and a second sealing ring is arranged between the gas sensor and the lining locking piece;
a buzzer is fixed in the lining piece and connected with the self-adaptive driving circuit of the gas sensor;
a display screen is fixed in the lining piece and connected with a self-adaptive driving circuit of the gas sensor;
the shell is provided with a display window, and the display window is correspondingly arranged above the display screen;
an LED alarm is fixed in the inner lining piece and connected with the self-adaptive driving circuit of the gas sensor;
the microcontroller is connected with a wireless communication module and a GNSS module.
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| CN111413601A (en) * | 2020-05-11 | 2020-07-14 | 国网陕西省电力公司电力科学研究院 | Overhead line partial discharge positioning device and positioning method based on ultrasonic array |
| CN112711206B (en) * | 2020-12-08 | 2024-04-09 | 武汉楚江水利水电工程质量检测有限公司 | Signal conditioning circuit, conditioning method and acquisition box |
| CN112950903A (en) * | 2021-02-05 | 2021-06-11 | 关学忠 | Oil field well head is easily fired, harmful gas comprehensive testing alarm system |
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