Two-wire system output oxygen detection device

Abstract

The utility model discloses a two-wire system output oxygen detection device which comprises a shell, an oxygen sensor, a data processing module and an electric processing module, the oxygen sensor, the data processing module and the electric processing module are all arranged in the shell, a wiring port is formed in the shell, and the electric processing module is electrically connected with an external power supply and a data receiving end through the wiring port; the shell is also provided with a gas channel; the oxygen sensor is communicated with the gas channel, gas to be detected flows through the oxygen sensor, the oxygen sensor reacts with oxygen in the gas to be detected, an electric signal is generated, and the electric signal is transmitted to the data processing module; the data processing module comprises a micro-control unit and an operational amplifier, the operational amplifier is used for converting the electric signals into differential signals and transmitting the differential signals to the micro-control unit, and the micro-control unit can convert the differential signals into corresponding digital signals. The micro-control unit can also calculate oxygen concentration data according to the digital signal, generate a concentration voltage signal according to the oxygen concentration data, and transmit the concentration voltage signal to the electric processing module; the electric processing module converts the concentration voltage signal into a concentration current signal and outputs the concentration current signal to a data receiving end; the electric processing module can respectively transform the input voltage DC24V of an external power supply into DC5V and DC2.5 V; the DC 2.5 V supplies power to the operational amplifier; meanwhile, the DC 5V is secondarily transformed into DC 3.3 V by the electric processing module, and the DC 3.3 V is used for supplying power to the micro-control unit; the power consumption and the working current of the whole machine can be reduced while the stability of the circuit is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of gas analysis instruments, and particularly relates to a two-wire output oxygen detection device. Background Art

[0002] The gases produced in chemical production have complex compositions and contain large amounts of combustible gases. Oxygen is a common gas raw material in chemical production. Combustible gases mixed with excessive oxygen concentrations can easily exceed the lower explosion limit, causing an explosion. For safety reasons, the oxygen content must be controlled below a set threshold to keep the combustible components in the gas below the lower explosion limit. Otherwise, combustible gases reaching a certain concentration can explode when exposed to heat, posing a threat to equipment and personnel. Therefore, oxygen concentration monitoring is a crucial guarantee for safe production in chemical gas production.

[0003] However, current oxygen detection devices have two major issues. First, two-wire oxygen detection devices consume high operating current and suffer from poor stability. Currently, in practical two-wire operating conditions, the operating current must be less than 3mA. Therefore, current two-wire oxygen detection devices require lower operating current, lower power consumption, and higher stability. Second, they have poor environmental adaptability, and measurement accuracy is affected by ambient temperature. In environments with large temperature fluctuations, measurement accuracy cannot be guaranteed. Utility Model Content

[0004] In view of this, the utility model provides a two-wire output oxygen detection device, which can not only achieve low power consumption while having high circuit stability, but also can perform temperature compensation and has strong environmental adaptability.

[0005] The utility model is realized through the following technical solutions:

[0006] A two-wire output oxygen detection device comprises: a housing, an oxygen sensor, a data processing module and an electrical processing module;

[0007] The oxygen sensor, data processing module and electrical processing module are all arranged in a housing. A wiring port is provided on the housing, and the electrical processing module is electrically connected to an external power supply and a data receiving terminal through the wiring port.

[0008] The housing is also provided with a gas channel; the oxygen sensor is connected to the gas channel, the gas to be measured flows through the oxygen sensor, the oxygen sensor reacts with the oxygen in the gas to be measured and generates an electrical signal, and the electrical signal is transmitted to the data processing module;

[0009] The data processing module includes a microcontroller unit and an operational amplifier. The operational amplifier is used to convert the aforementioned electrical signal into a differential signal and transmit it to the microcontroller unit. The microcontroller unit can convert the differential signal into a corresponding digital signal. The microcontroller unit can also calculate oxygen concentration data based on the digital signal and generate a concentration voltage signal based on the oxygen concentration data, which is then transmitted to the electrical processing module. The electrical processing module converts the concentration voltage signal into a concentration current signal and outputs it to the data receiving end.

[0010] The electrical processing module can transform the input voltage DC24V of the external power supply into DC5V and DC2.5V respectively; DC2.5V powers the operational amplifier; at the same time, the electrical processing module further transforms the DC5V into DC3.3V for powering the microcontroller unit.

[0011] Beneficial effects:

[0012] (1) The utility model provides a two-wire output oxygen detection device, which can measure the concentration of trace oxygen. Through primary voltage transformation, DC2.5V is used to power the operational amplifier, and then the DC5V is secondary transformed to DC3.3V to power the microcontroller unit. While improving the circuit stability, it can reduce the power consumption of the whole machine (power consumption is less than 1W) and the working current; at the same time, the explosion-proof performance of the two-wire output oxygen detection device is further improved, so that the oxygen detection device complies with the relevant provisions of GB / T3836.1-2021 and GB / T3836.4-2021 standards. It is an intrinsically safe equipment with an explosion-proof mark of "Ex ia IIC T3 Ga" and is suitable for gas concentration monitoring in Zone 0, Zone 1, and Zone 2, containing explosive mixtures of hydrogen and oxygen of grades IIA to IIC and temperatures of T1 to T3. It can also be used to measure the trace oxygen concentration in protective gases and mixed gases in water electrolysis hydrogen production, air separation nitrogen production, and other chemical industries.

[0013] (2) The utility model is provided with a primary voltage transformation signal processing circuit which can transform the voltage DC24V into DC5V and DC2.5V respectively, and realize the conversion of the concentration voltage signal into the concentration current signal. The circuit is stable, the working current is small, and the power consumption is low.

[0014] (3) The utility model is provided with a secondary voltage transformation circuit, which transforms DC5V into DC3.3V and can achieve voltage stabilization during the process of transforming DC5V into DC3.3V, thereby ensuring the stability of the circuit.

[0015] (4) The utility model sets a P-channel junction field effect transistor (JFET) between DC5V and the oxygen sensor. After the oxygen detection device is powered on, the P-channel junction field effect transistor is energized, and the working electrode Sens and the counter electrode Cnt of the oxygen sensor are disconnected, so that the normal collection of oxygen concentration can be achieved; when the oxygen detection device stops working, the working electrode Sens and the counter electrode Cnt of the oxygen sensor are short-circuited to prevent the working electrode of the oxygen sensor from accumulating a large amount of charge and causing polarization when the oxygen sensor is powered off for a long time, which is beneficial to extending the service life of the oxygen sensor.

[0016] (5) The present invention is also provided with a temperature acquisition module, which can collect the temperature data of the gas to be measured and transmit the temperature data to the data processing module; the micro control unit of the data processing module is embedded with a temperature compensation algorithm, which can compensate the calculation of the oxygen concentration according to the received temperature data of the gas to be measured, thereby obtaining a more accurate oxygen concentration, expanding the temperature use range of the two-wire output oxygen detection device, and improving environmental adaptability.

[0017] (6) The electrical processing module of the utility model provides a DC2.5V voltage to the temperature acquisition module, which can reduce the power consumption and operating current of the whole machine.

[0018] (7) The utility model is provided with a TTL data transmission line, which is convenient for downloading and debugging software programs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a front view of a two-wire output oxygen detection device of the utility model;

[0020] Figure 2 yes Figure 1 AA section view;

[0021] Figure 3 It is a voltage conversion and power supply flow chart;

[0022] Figure 4 This is the circuit diagram for converting 24V to DC5V and DC2.5V;

[0023] Figure 5 This is the circuit diagram for converting DC5V to DC3.3V;

[0024] Figure 6 It is the on-off control circuit of the reference electrode and the working electrode;

[0025] Figure 7 It is the temperature acquisition module circuit;

[0026] Among them, 1-stuffing box, 2-upper cover, 3-screw I, 4-spring washer, 5-flat washer, 6-intermediate housing, 7-compression fitting, 8-base, 9-top plate, 10-screw II, 11-copper column I, 12-bottom plate, 13-copper column II, 14-probe plate, 15-sensor pressure block, 16-oxygen sensor, 18-O-ring I, 19-explosion-proof disk, 20-O-ring II, 21-thermistor fixing plate, 22-screw III. DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0028] Embodiment 1:

[0029] This embodiment provides a two-wire output oxygen detection device, see the attached Figure 1 and 2 , including a housing, an oxygen sensor 16, a data processing module and an electrical processing module;

[0030] The oxygen sensor 16, the data processing module, and the electrical processing module are all disposed within a housing. The housing is provided with a wiring port, through which the electrical processing module is electrically connected to an external power supply and a data receiving terminal (such as a PLC). The electrical processing module is used to supply power to the data processing module and to convert voltage signals into current signals.

[0031] The housing is also provided with a gas passage; an oxygen sensor 16 is connected to the gas passage, and the gas to be measured flows through the oxygen sensor 16, the oxygen sensor 16 reacts with the oxygen in the gas to be measured and generates an electrical signal, and transmits the electrical signal to the data processing module;

[0032] The data processing module includes a microcontroller unit (MCU) and an operational amplifier. The operational amplifier is used to calculate and convert the aforementioned electrical signals into differential signals and transmit them to the MCU. The MCU is equipped with an AD acquisition port that can convert the differential signals into corresponding digital signals. The MCU can also calculate the oxygen concentration data based on the digital signals and generate a concentration voltage signal based on the oxygen concentration data, which is then transmitted to the electrical processing module; the electrical processing module converts the concentration voltage signal into a concentration current signal and outputs it to the data receiving end.

[0033] See attached Figure 3 The electrical processing module can transform the input voltage DC24V of the external power supply into DC5V and DC2.5V respectively; DC2.5V is used to power the operational amplifier; at the same time, the electrical processing module further transforms the DC5V into DC3.3V for powering the micro control unit;

[0034] This embodiment provides a two-wire output oxygen detection device capable of measuring trace oxygen concentration. Through primary voltage transformation, DC2.5V is used to power an operational amplifier. A voltage regulator circuit then uses a secondary voltage transformation from DC5V to DC3.3V to power a microcontroller unit. This improves circuit stability while reducing overall power consumption (less than 1W) and operating current. Furthermore, the explosion-proof performance of the two-wire output oxygen detection device is further enhanced, ensuring compliance with the relevant provisions of GB / T3836.1-2021 and GB / T3836.4-2021 standards. It is intrinsically safe and carries the explosion-proof mark "Ex ia IIC T3 Ga." It is suitable for monitoring gas concentrations in Zones 0, 1, and 2, containing explosive mixtures of hydrogen and oxygen in Classes IIA to IIC and temperatures in Groups T1 to T3. It can also be used to measure trace oxygen concentrations in protective gases and mixed gases used in hydrogen production by water electrolysis, nitrogen production by air separation, and other chemical industries.

[0035] The electrical processing module is equipped with a primary voltage transformation signal processing circuit and a secondary voltage transformation circuit. The primary voltage transformation signal processing circuit is used to transform the voltage DC24V into DC5V and DC2.5V respectively, and is also used to realize the conversion of concentration voltage signal into concentration current signal. The secondary voltage transformation circuit is used to transform DC5V into DC3.3V.

[0036] See attached Figure 4 ,The primary voltage transformation signal processing circuit includes transistor Q3, two-wire current loop transmitter, capacitor C12, voltage stabilizing diode D6 and transient suppression diode TVS1;

[0037] There are eight pins on the two-wire current loop transmitter, namely Vreg pin, Vregf pin, Iin pin, Iret pin, V+ pin, B pin, E pin and Io pin;

[0038] The V+ pin is used to input DC24V, the Vreg pin is used to output DC5V, and the Vregf pin is used to output DC2.5V;

[0039] The Iin pin is electrically connected to the microcontroller unit and has a series resistor R14 for inputting a concentration voltage signal (0.4-2V). The Io pin is electrically connected to an external data receiving terminal for outputting a concentration current signal (4-20mA). The Iret pin is grounded.

[0040] The three pins of the transistor Q3 are a base-collector pin, a collector pin, and an emitter pin, respectively. The base-collector pin is electrically connected to the B pin of the two-wire current loop transmitter, the collector pin is electrically connected to the V+ pin of the two-wire current loop transmitter, and the emitter pin is electrically connected to the E pin of the two-wire current loop transmitter.

[0041] Capacitor C12, voltage stabilizing diode D6 and transient suppression diode TVS1 are respectively connected in parallel between the V+ pin and Io pin of the two-wire current loop transmitter to achieve primary voltage stabilization;

[0042] Preferably, the two-wire current loop transmitter uses XTR115UA current loop transmitter, which has low power consumption and can convert voltage signals into current signal output; the resistor R14 is 10KΩ;

[0043] See attached Figure 5 , the secondary voltage transformation circuit includes: voltage stabilizing chip U1, voltage stabilizing diode D5, voltage stabilizing diode D3, voltage stabilizing diode D1, voltage stabilizing diode D4, capacitor C1 and capacitor C2;

[0044] The voltage regulator chip U1 is provided with four pins, namely IN pin, OUT pin, PD pin and GND pin;

[0045] Both the PD pin and GND are grounded;

[0046] The IN pin is electrically connected to the DC5V voltage, and the Zener diode D5, Zener diode D3 and capacitor C1 are connected in parallel between the IN pin and the GND pin respectively; this is used to achieve DC5V input voltage regulation;

[0047] The voltage regulator chip U1 is used to reduce the DC5V voltage to DC3.3V;

[0048] The OUT pin is used to output DC3.3V. The Zener diode D1, Zener diode D4 and capacitor C2 are connected in parallel between the OUT pin and the GND pin respectively to achieve DC3.3V output voltage regulation;

[0049] Preferably, the capacitor C1 and the capacitor C2 are both 0.01 μF; the voltage regulator diode D5, the voltage regulator diode D3, the voltage regulator diode D1 and the voltage regulator diode D4 are all ISMA4734 models;

[0050] In one specific embodiment, a P-channel junction field effect transistor (JFET) is provided between the DC5V output terminal and the oxygen sensor 16;

[0051] The oxygen sensor 16 is provided with a working electrode Sens and a counter electrode Cnt;

[0052] The source and drain of the P-channel junction field-effect transistor are connected to the working electrode Sens and counter electrode Cnt of the oxygen sensor 16, respectively; the gate of the P-channel junction field-effect transistor is connected to a DC5V potential via a resistor R25; after the oxygen detection device is powered on, the P-channel junction field-effect transistor is energized, and the working electrode Sens and counter electrode Cnt of the oxygen sensor 16 are disconnected, enabling normal collection of oxygen concentration; when the oxygen detection device stops working, the working electrode Sens and counter electrode Cnt of the oxygen sensor 16 are short-circuited to prevent the working electrode of the oxygen sensor 16 from accumulating a large amount of charge and causing polarization when the oxygen sensor 16 is powered off for a long time, which is beneficial to extending the service life of the oxygen sensor 16. Preferably, the resistor R25 is 1MΩ;

[0053] In a specific embodiment, see the attached Figure 1 and 2 The housing includes an upper cover 2, an intermediate shell 6 and a base 8; the upper cover 2, the intermediate shell 6 and the base 8 are coaxially connected in sequence; let the direction where the upper cover 2 is located be upward, and the direction where the base is located be downward;

[0054] A stuffing box 1 is provided on the top of the upper cover 2, and the stuffing box is provided with the wiring port. A data line (not shown) passes through the wiring port. The data line has five cores, two of which are DC24V input and 4-20mA output (i.e., for outputting the aforementioned concentration current signal); the other three cores are TTL data transmission lines for software program downloading and debugging.

[0055] The outer circumference of the upper cover 2 is provided with an annular edge I. The bottom end of the upper cover 2 is coaxially located inside the upper end of the intermediate shell 6. The annular edge I of the upper cover 2 abuts against the upper end surface of the intermediate shell 6. A number of fixing members are provided along the annular edge I for achieving a fixed connection between the upper cover 2 and the intermediate shell 6. Preferably, each fixing member is a screw I3 (hexagon socket head screw), a spring washer 4, and a flat washer 5.

[0056] The bottom end of the intermediate housing 6 is provided with an outward-turned annular edge II. The base 8 is a cylindrical stepped structure, including a small-diameter section located at the top and a large-diameter section located at the bottom, with a stepped surface formed between the small-diameter section and the large-diameter section. The small-diameter section of the base 8 is coaxially located within the intermediate housing 6. The annular edge II of the intermediate housing 6 abuts against the stepped surface of the base 8. Several fixing members are provided along the annular edge II for achieving a fixed connection between the intermediate housing 6 and the base 8.

[0057] The side of the base 8 is provided with two radial blind holes, namely the air inlet blind hole and the air outlet blind hole (the aforementioned gas channel is the air inlet blind hole and the air outlet blind hole); the top of the base 8 is provided with a mounting groove;

[0058] The oxygen sensor 16 includes an oxygen sensor body and a probe plate 14; the oxygen sensor body is fixedly disposed in the mounting groove, and an air inlet and an air outlet are provided at the bottom of the oxygen sensor body. The air inlet communicates with the air inlet blind hole of the base 8, and the air outlet communicates with the air outlet blind hole of the base 8; the radial outer ends of the two blind holes are respectively connected to a ferrule joint 7 to ensure a seal for gas inflow and outflow; explosion-proof discs 19 are provided at the air inlet and air outlet of the oxygen sensor body; an O-ring I 18 is provided at the outer periphery of the bottom end of the oxygen sensor body in contact with the mounting groove to isolate the gas to be measured from the data processing module and the electrical processing module;

[0059] The upper end of the oxygen sensor body is fixedly mounted on the intermediate housing 6. The probe plate 14 is fixedly mounted on the top of the oxygen sensor body. Two sets of probes are mounted on the probe plate 14. The two sets of probes extend deep into the sensor body. The end of one set of probes serves as the aforementioned working electrode Sens, and the end of the other set of probes serves as the aforementioned counter electrode Cnt.

[0060] In a specific embodiment, the top of the oxygen sensor body is fixedly connected to the intermediate housing 6 through a sensor pressing block 15; the probe plate 14 is fixedly arranged on the top of the sensor pressing block 15; and a through hole for passing the probe is provided on the probe plate sensor pressing block 15;

[0061] The electrical processing module and the data processing module are integrated on one or more PCB boards. Figure 2 The electrical processing module and the data processing module are integrated on two PCB boards, namely the top plate 9 and the bottom plate 12. The bottom plate 12 is fixedly supported on the intermediate housing 6 by a number of copper pillars II 13, and the top plate 9 is fixedly supported on the copper pillars II 13 by a number of copper pillars I 11 and screws II 10. The top plate 9 and the bottom plate 12 are electrically connected through a pin and female header. The probe board 14 is electrically connected to the bottom plate 12. Specifically, the probe board 14 has two leads, which are the leads of the working electrode Sens and the counter electrode Cnt. The two leads are respectively welded to the corresponding pins on the bottom plate 12.

[0062] Preferably, the screws II 10 are twelve cross recessed pan head screws M3; the copper pillars I 11 are six copper pillars 3×9, and the copper pillars II 13 are six copper pillars 3×6; the pin and female headers are seven-core pins and seven-core sockets respectively;

[0063] In a specific embodiment, both the MCU and the operational amplifier are low-power, stable chips to further reduce power consumption and improve stability.

[0064] Directions:

[0065] Secure the base to the support bracket to be installed, keeping the two-wire output oxygen detection device vertical. Slide the φ6 stainless steel tube onto the compression fitting 7 and tighten the compression nut to ensure the air path is sealed. Before connecting the instrument, purge the pipeline to ensure that the front and rear pipelines are clean and free of particles to prevent blockage of the measurement air path after ventilation.

[0066] Working principle:

[0067] The electrical processing module converts the DC24V voltage into DC2.5V and DC5V through primary voltage transformation; the DC2.5V is used to power the operational amplifier, and the electrical processing module converts the DC5V into DC3.3V through secondary voltage transformation to power the microcontroller unit.

[0068] The oxygen sensor 16 reacts with the oxygen in the gas to be measured and generates an electrical signal, which is then transmitted to the data processing module. The operational amplifier in the data processing module converts the electrical signal into a differential signal. The microcontroller unit receives the differential signal and converts it into a corresponding digital signal. The microcontroller unit can also calculate oxygen concentration data based on the digital signal and generate a concentration voltage signal based on the oxygen concentration data, which is then transmitted to the electrical processing module. The electrical processing module converts the concentration voltage signal into a concentration current signal and outputs it to a data receiving terminal, such as a PLC.

[0069] This embodiment provides a two-wire output oxygen detection device capable of measuring trace oxygen concentration. Through primary voltage transformation, DC2.5V is used to power an operational amplifier. A voltage stabilization circuit then transforms the DC5V to DC3.3V to power a microcontroller unit. This improves circuit stability while reducing overall power consumption (less than 1W) and operating current.

[0070] Example 2:

[0071] In this embodiment, based on the first embodiment, a two-wire output oxygen detection device further includes a temperature acquisition module, which is used to collect temperature data of the gas to be measured and transmit the temperature data to the data processing module;

[0072] The data processing module's microcontroller unit is embedded with a temperature compensation algorithm, which can compensate for the oxygen concentration calculation based on the received temperature data of the gas to be measured, thereby obtaining a more accurate oxygen concentration, expanding the temperature range of the two-wire output oxygen detection device, and improving environmental adaptability.

[0073] The electrical processing module provides DC2.5V voltage to the temperature acquisition module, which can reduce the power consumption and operating current of the whole machine.

[0074] See attached Figure 7The temperature acquisition module includes a thermistor RT1 and a resistor R4. The thermistor RT1 and the resistor R4 are connected in series between a 2.5V potential and a 0 potential (i.e., ground). The intermediate potential between the thermistor RT1 and the resistor R4 is electrically connected to the microcontroller unit, specifically to the AD acquisition port of the microcontroller unit. The microcontroller unit can obtain the temperature data of the gas to be measured by obtaining the resistance value of the thermistor RT1.

[0075] The temperature compensation algorithm is a mathematical model obtained through a large number of temperature tests. Specifically, the algorithm obtains oxygen concentration data from the oxygen sensor at different temperatures while keeping the oxygen concentration constant. The detection data is then curve-fitted to establish a mathematical model for how the oxygen detection data changes with temperature. Based on the mathematical model, the true value of the oxygen concentration is reversely calculated using the oxygen concentration data and the temperature data of the gas to be measured.

[0076] This embodiment compensates the calculation of the trace oxygen concentration based on temperature data, thereby making the calculation of the oxygen concentration more accurate and the applicable temperature of the device wider.

[0077] See attached Figure 2 The top of the base 8 is also provided with a temperature collection hole, which is connected to the air inlet blind hole of the base 8. A thermistor fixing plate 21 is located at the top of the temperature collection hole. Thermistor RT1 is fixed to the thermistor fixing plate 21 by screws III 22 to obtain the temperature of the gas to be measured. An O-ring II 20 (d6×1.8) is installed between the temperature collection hole and the thermistor fixing plate 21.

[0078] Preferably, the screws III 22 are six cross-recessed pan head screws M3;

[0079] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A two-wire output oxygen detection device, characterized in that: include: Housing, oxygen sensor, data processing module and electrical processing module; The oxygen sensor, data processing module and electrical processing module are all arranged in a housing. A wiring port is provided on the housing, and the electrical processing module is electrically connected to an external power supply and a data receiving terminal through the wiring port. The housing is also provided with a gas channel; the oxygen sensor is connected to the gas channel, the gas to be measured flows through the oxygen sensor, the oxygen sensor reacts with the oxygen in the gas to be measured and generates an electrical signal, and the electrical signal is transmitted to the data processing module; The data processing module includes a microcontroller unit and an operational amplifier. The operational amplifier is used to convert the aforementioned electrical signal into a differential signal and transmit it to the microcontroller unit. The microcontroller unit can convert the differential signal into a corresponding digital signal. The microcontroller unit can also calculate oxygen concentration data based on the digital signal and generate a concentration voltage signal based on the oxygen concentration data, which is then transmitted to the electrical processing module. The electrical processing module converts the concentration voltage signal into a concentration current signal and outputs it to the data receiving end. The electrical processing module can transform the input voltage DC24V of the external power supply into DC5V and DC2.5V respectively; DC2.5V powers the operational amplifier; at the same time, the electrical processing module further transforms the DC5V into DC3.3V for powering the microcontroller unit.

2. A two-wire output oxygen detection device as claimed in claim 1, characterized in that: The electrical processing module is equipped with a primary voltage transformation signal processing circuit and a secondary voltage transformation circuit. The primary voltage transformation signal processing circuit is used to transform the DC24V voltage into DC5V and DC2.5V respectively, and is also used to realize the conversion of concentration voltage signal into concentration current signal. The secondary voltage transformation circuit is used to transform DC5V into DC3.3V.

3. A two-wire output oxygen detection device as claimed in claim 2, characterized in that: The primary voltage transformation signal processing circuit includes a transistor Q3, a two-wire current loop transmitter, a capacitor C12, a voltage stabilizing diode D6 and a transient suppression diode TVS1; There are eight pins on the two-wire current loop transmitter, namely Vreg pin, Vregf pin, Iin pin, Iret pin, V+ pin, B pin, E pin and Io pin; The V+ pin is used to input DC24V, the Vreg pin is used to output DC5V, and the Vregf pin is used to output DC2.5V; The Iin pin is electrically connected to the microcontroller unit and has a series resistor R14 for inputting a concentration voltage signal; the Io pin is electrically connected to an external data receiving terminal for outputting a concentration current signal; the Iret pin is grounded; The three pins of the transistor Q3 are a base-collector pin, a collector pin, and an emitter pin, respectively. The base-collector pin is electrically connected to the B pin of the two-wire current loop transmitter, the collector pin is electrically connected to the V+ pin of the two-wire current loop transmitter, and the emitter pin is electrically connected to the E pin of the two-wire current loop transmitter. The capacitor C12, the voltage stabilizing diode D6 and the transient suppression diode TVS1 are respectively connected in parallel between the V+ pin and the Io pin of the two-wire current loop transmitter.

4. A two-wire output oxygen detection device as claimed in claim 2, characterized in that: The secondary voltage transformation circuit includes: voltage stabilizing chip U1, voltage stabilizing diode D5, voltage stabilizing diode D3, voltage stabilizing diode D1, voltage stabilizing diode D4, capacitor C1 and capacitor C2; The voltage regulator chip U1 is provided with four pins, namely IN pin, OUT pin, PD pin and GND pin; Both the PD pin and GND are grounded; The IN pin is electrically connected to the DC5V voltage, and the Zener diode D5, Zener diode D3 and capacitor C1 are connected in parallel between the IN pin and the GND pin respectively; The voltage regulator chip U1 is used to reduce the DC5V voltage to DC3.3V; The OUT pin is used to output DC3.3V. The Zener diode D1, Zener diode D4 and capacitor C2 are connected in parallel between the OUT pin and the GND pin respectively.

5. A two-wire output oxygen detection device as claimed in claim 1, characterized in that: A P-channel junction field effect transistor is provided between the output end of the DC5V voltage and the oxygen sensor; The oxygen sensor is provided with a working electrode Sens and a counter electrode Cnt; The source and drain of the P-channel junction field effect transistor are connected to the working electrode Sens and the counter electrode Cnt of the oxygen sensor respectively; the gate of the P-channel junction field effect transistor is connected to a DC5V potential through a resistor R25; After the oxygen detection device is powered on, the P-channel junction field effect transistor is energized, and the working electrode Sens and the counter electrode Cnt of the oxygen sensor are disconnected; When the oxygen detection device stops working, the working electrode Sens and the counter electrode Cnt of the oxygen sensor are short-circuited.

6. A two-wire output oxygen detection device according to any one of claims 1 to 5, characterized in that: A two-wire output oxygen detection device further includes a temperature acquisition module, which is used to collect temperature data of the gas to be measured and transmit the temperature data to the data processing module; The microcontrol unit of the data processing module is embedded with a temperature compensation algorithm, which can compensate the calculation of the oxygen concentration according to the received temperature data of the gas to be measured.

7. A two-wire output oxygen detection device as claimed in claim 6, characterized in that: The electrical processing module provides DC2.5V voltage to the temperature acquisition module.

8. A two-wire output oxygen detection device as claimed in claim 7, characterized in that: The temperature acquisition module includes a thermistor RT1 and a resistor R4. The thermistor RT1 and the resistor R4 are set in series between the potential of 2.5V and the potential of 0. The intermediate potential of the thermistor RT1 and the resistor R4 is electrically connected to the microcontroller unit; the microcontroller unit can obtain the temperature data of the gas to be measured by obtaining the resistance value of the thermistor RT1.

9. A two-wire output oxygen detection device as claimed in claim 8, characterized in that: The housing includes an upper cover, an intermediate shell and a base; the upper cover, the intermediate shell and the base are coaxially connected in sequence; the direction where the upper cover is located is upward, and the direction where the base is located is downward; A stuffing box is provided on the top of the upper cover, and the wiring port is provided on the stuffing box; a data cable passes through the wiring port, and the data cable has five cores, two of which are used for DC24V input and concentration current signal output respectively, and the other three cores are TTL data transmission lines for software program downloading and debugging; There are two radial blind holes on the side of the base, one for air inlet and one for air outlet; and a mounting slot is provided on the top of the base. The oxygen sensor includes an oxygen sensor body and a probe plate. The oxygen sensor body is fixedly mounted in the mounting groove. An air inlet and an air outlet are provided at the bottom of the oxygen sensor body. The air inlet communicates with the air inlet blind hole of the base, and the air outlet communicates with the air outlet blind hole of the base. Explosion-proof discs are provided at both the air inlet and the air outlet of the oxygen sensor body. An O-ring I is provided at the outer periphery of the bottom end of the oxygen sensor body where it contacts the mounting groove. The upper end of the oxygen sensor body is fixed to the intermediate housing, and the probe plate is fixed to the top of the oxygen sensor body. The probe plate is provided with two sets of probes, which penetrate deep into the sensor body; the end of one set of probes is the working electrode Sens, and the end of the other set of probes is the counter electrode Cnt; The electrical processing module and the data processing module are integrated on one or more PCB boards, which are fixed in the housing; the probe board is electrically connected to the PCB board; A temperature collection hole is provided at the top of the base, which is connected to the air inlet blind hole of the base. A thermistor fixing plate is provided at the top of the temperature collection hole. The thermistor RT1 is fixed on the thermistor fixing plate to obtain the temperature of the gas to be measured; an O-ring II is provided between the temperature collection hole and the thermistor fixing plate.

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