Digital processing circuit of catalytic combustion sensor

Abstract

The utility model relates to a digital processing circuit of a catalytic combustion sensor, in the digital processing circuit, one end of a first detection resistor R1 is connected with one end of an internal compensation element C of a catalytic sensor CG1, the other end of the first detection resistor R1 is connected with the other end of a second detection resistor R2, and one end of the second detection resistor R2 is connected with one end of an internal detection element D of the catalytic sensor CG1; the other end of the compensation element C and the other end of the detection element D are connected with the first input end of the microprocessor IC1. The other end of the second detection resistor R2 is connected with the second input end of the microprocessor IC1. The wiring plug-in JP1 is used for performing serial port communication with the microprocessor IC1 and the outside; and the linear voltage-stabilized power supply IC2 is used for converting a power supply of the wiring plug-in JP1 into a voltage-stabilized power supply so as to supply power to the catalytic sensor CG1. The device has the beneficial effect that the sensor can be conveniently and independently replaced.

Description

Technical Field

[0001] This application relates to the technical field of catalytic combustion sensors, and in particular to a digital processing circuit for a catalytic combustion sensor. Background Technology

[0002] Catalytic combustion sensors are common gas detection sensors, typically consisting of a detection element and a compensation element. Their basic principle is that when a combustible gas comes into contact with the catalyst on the detection element, flameless combustion occurs, causing the carrier temperature to rise. This temperature change leads to an increase in the resistance of the platinum wire within the detection element, which can be detected by a circuit to further measure the gas concentration.

[0003] Reference Figure 1 To facilitate the measurement of changes in the detection element, the conventional application circuit connects the detection element D and the compensation element C in series, and adds a pair of auxiliary detection resistors R1 and R2. One end of the first detection resistor R1 is connected in series with the detection element D, and the other end is connected in series with a potentiometer W. The potentiometer W is connected in series with one end of the second detection resistor R2, and the other end of the second detection resistor R2 is connected in series with the compensation element C. The adjustment terminal of the potentiometer W and the midpoint between the detection element D and the compensation element C form a bridge output to form a Whitworth bridge circuit, which outputs an electrical signal proportional to the concentration of combustible gas. One end of the first detection resistor R1 and the other end of the second detection resistor R2 are connected to the test voltage.

[0004] Because the output signal of the catalytic combustion sensor is relatively small, an amplification circuit is generally required in related technologies to achieve accurate measurement, which necessitates an operational amplifier. Secondly, due to zero-point drift and inconsistent sensitivity in the catalytic combustion sensor, a potentiometer W is needed in the circuit for zero-point adjustment and amplification adjustment. This results in a relatively complex processing circuit for the catalytic combustion sensor, and the need to repeatedly adjust the potentiometer W during production, making mass production inconvenient.

[0005] Because the gas reaction of catalytic combustion sensors consumes the catalyst, their lifespan is relatively short, generally around 3 years, necessitating on-site sensor replacement. Furthermore, since gas alarms used in industrial settings are explosion-proof and consist of multiple circuit boards, with the sensor corresponding to one of these boards, independent sensor replacement and on-site gas calibration are inconvenient. Utility Model Content

[0006] To facilitate independent sensor replacement, this application provides a digital processing circuit for a catalytic combustion sensor to directly output digital gas concentration values. The digital processing circuit is integrated onto a single circuit board, employing the following technical solution:

[0007] A digital processing circuit for a catalytic combustion sensor includes:

[0008] Catalytic sensor CG1;

[0009] The first detection resistor R1 is connected at one end to one end of the compensation element C inside the catalytic sensor CG1;

[0010] The second detection resistor R2 has one end connected to one end of the detection element D inside the catalytic sensor CG1; the other end of the first detection resistor R1 is connected to the other end of the second detection resistor R2; and the other end of the compensation element C is connected to the other end of the detection element D.

[0011] The microprocessor IC1 has a first input terminal connected to the connection terminal of the compensation element C and the other end of the detection element D, and a second input terminal connected to the connection terminal of the other end of the first detection resistor R1 and the second detection resistor R2.

[0012] The wiring plug JP1 is connected to the microprocessor IC1 and is used for serial communication with external devices, and is powered by an external power source.

[0013] A linear regulated power supply IC2 is connected to the wiring plug JP1 and is used to convert the power supply into a regulated power supply; the power output terminal of the linear regulated power supply IC2 is used to power the catalytic sensor CG1.

[0014] By adopting the above technical solution, the microprocessor IC1 has a 16-bit high-precision AD converter and internal reference, as well as a differential operational amplifier (OPA) function. Using the microprocessor IC1, linear power supply IC2, and connector JP1, it is possible to process the electrical signals of the catalytic sensor CG1 while placing all circuitry on a 25mm diameter circuit board, ensuring a safe distance from the explosion-proof probe housing and avoiding limitations imposed by the confined space inside the housing. Furthermore, the highly integrated circuitry enables digital processing of the catalytic sensor CG1, allowing for modular manufacturing via serial port commands, resulting in a simple manufacturing process and high integration. The system offers reliable quality and enables modular maintenance on-site, eliminating the need for on-site calibration. Although the microprocessor IC1 operates over a wide voltage range, the conversion results of its internal AD converter are directly related to the reference voltage. To avoid the microprocessor IC1's operating voltage affecting the AD conversion results, the reference voltage for AD conversion can be the one internal to the microprocessor IC1. This ensures that changes in external power supply do not affect the AD conversion results and therefore do not affect the gas concentration measurement. Consequently, detection accuracy is improved, and when replacing the catalytic sensor CG1, only the explosion-proof probe needs to be replaced, without replacing the entire unit, making replacement convenient.

[0015] Optionally, the digitization processing circuit further includes:

[0016] The third resistor is connected in series between the first input terminal of the microprocessor IC1 and the connection terminal between the compensation element C and the other end of the detection element D;

[0017] The fourth resistor is connected in series with the second input terminal of the microprocessor IC1 and the other end of the first detection resistor R1 and the second detection resistor R2.

[0018] By adopting the above technical solution, current limiting protection is provided for the microprocessor IC1.

[0019] Optionally, the digitization processing circuit further includes:

[0020] The fifth resistor R5 has one end connected to the control output terminal of the microprocessor IC1 and the other end connected to the control input terminal of the linear regulated power supply IC2; the microprocessor IC1 is used to control the on / off state of the linear regulated power supply IC2.

[0021] By adopting the above technical solution, the catalytic sensor CG1 has a low internal resistance when it is cold, resulting in a large current consumption at the moment of power-on. Then, as power is gradually applied, the internal resistance gradually increases and the current decreases. Many industrial explosion-proof alarms are connected to the controller via a bus connection. When the system is powered on, the simultaneous power-on of numerous alarms can cause a surge in power to the power supply system. To avoid this, a large-capacity power supply is generally used, but this results in unnecessary waste.

[0022] In a bus system, each alarm has a unique address number, facilitating bus inspections. Using this address number to delay power-on can avoid the aforementioned situation.

[0023] After the microprocessor IC1 powers on, it controls the linear power supply IC2 to shut off the power supply to the catalytic converter CG1. The microprocessor IC1 receives the local address number of the alarm via the serial port, uses this to generate different time delays, and then controls the linear power supply IC2 to power the catalytic converter CG1. This ensures that the catalytic converter CG1 in all alarms on the bus is powered on sequentially, avoiding concentrated power-on and reducing the impact on the power supply.

[0024] Optionally, the wiring plug-in JP1 includes an RXD terminal, a TXD terminal, a GND terminal, and a V33 terminal; the RXD terminal, TXD terminal, GND terminal, and V33 terminal are all connected to the microprocessor IC1, the RXD terminal and TXD terminal are used to output digital signals to the outside, and the V33 terminal is used to connect to an external power supply.

[0025] Optionally, the linear regulated power supply IC2 includes a Vin terminal, a Vout terminal, a GND terminal, and an EN terminal; the Vin terminal is connected to the V33 terminal of the connector JP1, the GND terminal is connected to the GND terminal of the connector JP1 and grounded, the Vout terminal is the power output terminal, and the EN terminal is the control input terminal.

[0026] Optionally, the Vout terminal of the linear regulated power supply IC2 is also connected to a capacitor C1, and the negative terminal of the capacitor C1 is grounded.

[0027] In summary, this application has at least the following beneficial effects:

[0028] 1. The purpose of setting up the microprocessor IC1, linear power supply IC2, and wiring plug JP1 is that the microprocessor IC1 has a 16-bit high-precision AD converter, an internal reference, and a differential operational amplifier (OPA) function. Using the microprocessor IC1, linear power supply IC2, and wiring plug JP1, the electrical signal processing of the catalytic converter sensor CG1 can be achieved, and all circuitry can be placed on a 25mm diameter circuit board while ensuring a safe distance from the explosion-proof probe housing, avoiding the limitations of the confined space inside the explosion-proof probe housing. Furthermore, due to the highly integrated circuitry, the catalytic converter sensor CG1 achieves digital processing, enabling modular manufacturing via serial port commands. The manufacturing process is simple, and the integration ensures high quality and reliability, enabling modular maintenance in engineering fields and eliminating the need for on-site calibration. Although the microprocessor IC1 operates within a wide voltage range, the conversion result of its internal AD converter is directly related to the reference voltage. To avoid the microprocessor IC1's operating voltage affecting the AD conversion result, the reference voltage for AD conversion can be the internal voltage of the microprocessor IC1. This way, regardless of changes in the external power supply, the AD conversion result will not be affected, and thus, the gas concentration measurement will not be affected. Therefore, on the one hand, the detection accuracy is improved, and on the other hand, when replacing the catalytic sensor CG1, only the explosion-proof probe needs to be replaced, without replacing the entire unit, making replacement convenient.

[0029] 2. The purpose of microprocessor CG1 controlling the on / off switching of linear regulated power supply IC2 is that when the catalytic sensor CG1 is cold, its internal resistance is small, resulting in a large current consumption at the moment of power-on. As power is gradually applied, the internal resistance gradually increases, and the current decreases. Many industrial explosion-proof alarms use a bus connection to the controller. When the system powers on, if numerous alarms power on simultaneously, it can impact the power supply system. To avoid this, a large-capacity power supply is generally used, but this results in unnecessary waste. In a bus system, each alarm has a fixed address number, facilitating bus inspection. Delaying power-on using this address number avoids this situation. After microprocessor IC1 powers on, it controls linear regulated power supply IC2 to shut off the power supply to the catalytic sensor CG1. Microprocessor IC1 receives the alarm's local address number via serial port, uses this to generate different time delays, and then controls linear regulated power supply IC2 to power the catalytic sensor CG1. This ensures that the catalytic sensors CG1 in all alarms on the bus are powered sequentially, avoiding concentrated power-on and reducing the impact on the power supply.

[0030] 3. Catalytic combustion alarms used in industrial settings operate within a temperature range of -40 to 70°C. Within this wide temperature range, the sensitivity of the catalytic combustion sensor varies. This effect can be eliminated through temperature compensation. The microprocessor IC1 has an internal temperature measurement function. Using this function, after detecting the current ambient temperature, and based on pre-tested relationships between the sensor's sensitivity changes at different temperatures and room temperature (25°C), the microprocessor IC1 can compensate for the sensitivity according to a pre-set program, thus eliminating the influence of temperature changes on gas concentration testing. Attached Figure Description

[0031] Figure 1 This is a circuit diagram of the Whitworth bridge circuit for a catalytic sensor based on related technologies.

[0032] Figure 2 This is a circuit diagram of the digital processing circuit of this application. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the appendices of the embodiments of this utility model will be described below. Figure 1 -Appendix Figure 2 The technical solutions in the embodiments of this utility model are clearly and completely described herein. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0034] This application discloses a digital processing circuit for a catalytic combustion sensor. (Refer to...) Figure 2 The digital processing circuit may include a catalytic sensor CG1, a first detection resistor R1, a second detection resistor R2, a microprocessor IC1, a wiring plug JP1, and a linear regulated power supply IC2.

[0035] The microprocessor IC1 can be a BH66F5242, which features a 16-bit high-precision AD converter, an internal reference, and a differential operational amplifier (OPA). The linear regulator IC2 can be a BL9198-25.

[0036] In this configuration, one end of the first detection resistor R1 is connected to one end of the compensation element C inside the catalytic sensor CG1, and the other end is connected to the other end of the second detection resistor R2. The connection point of the other ends of the first detection resistor R1 and the second detection resistor R2 is connected to the second input terminal of the microprocessor IC1. One end of the second detection resistor R2 is connected to one end of the detection element D inside the catalytic sensor CG1, and one end of the second detection resistor R2 is also grounded. The other end of the compensation element C is connected to the other end of the detection element D, and the connection point is connected to the first input terminal of the microprocessor IC1.

[0037] The wiring plug JP1 includes an RXD terminal, a TXD terminal, a GND terminal, and a V33 terminal; the RXD terminal, TXD terminal, GND terminal, and V33 terminal are all connected to the microprocessor IC1. The RXD terminal and TXD terminal are used to output digital signals to the outside, and the V33 terminal is used to connect to an external power supply, which usually provides a 3.3V voltage.

[0038] The linear regulated power supply IC2 includes a Vin terminal, a Vout terminal, a GND terminal, and an EN terminal. The Vin terminal is connected to the V33 terminal of connector JP1, and the GND terminal is connected to the GND terminal of connector JP1 and grounded. The Vout terminal is the power output terminal V25, representing 2.5V, used to power the catalytic sensor CG1. The Vout terminal is connected to one end of the first sensing resistor R1. The EN terminal is the control input terminal.

[0039] Furthermore, the digital processing circuit also includes a capacitor C1 and a fifth resistor R5; wherein, the positive terminal of capacitor C1 is connected to the Vout terminal, and the negative terminal is grounded. One end of the fifth resistor R5 is connected to the control output IO terminal of microprocessor IC1, and the other end is connected to the EN terminal.

[0040] Furthermore, the digital processing circuit also includes a third resistor R3 and a fourth resistor R4; wherein, the third resistor R3 is connected in series between the other end of the detection element D and the compensation element C and the first input terminal of the microprocessor IC1. The fourth resistor R4 is connected in series between the second input terminal of the microprocessor IC1 and the other end of the connection between the first detection resistor R1 and the second detection resistor R2.

[0041] The performance of the catalytic sensor CG1 is affected by many factors, one of which is the stability of the power supply voltage.

[0042] The voltage output of the linear power supply IC2 has a certain error, but for a specific linear power supply IC2 chip, its output error is fixed. This technical solution integrates the linear power supply IC2 and the catalytic sensor CG1 into a single circuit. This means that the supply voltage to the catalytic sensor CG1 is constant and within the allowable supply error range, thus making the performance of the catalytic sensor CG1 more stable.

[0043] The circuit's input voltage is marked as 3.3V. Due to the error in the front-end power supply output, the actual input voltage range is allowed to be 3-4V. Within this voltage range, the microprocessor IC1 works normally, and the linear regulated power supply IC2 also works normally.

[0044] Although the microprocessor IC1 can operate within a wide voltage range, the conversion result of its internal AD converter is directly related to the reference voltage. To avoid the microprocessor IC1's operating voltage affecting the AD conversion result, the reference voltage for AD conversion is the one internal to the microprocessor IC1. This way, regardless of changes in the external power supply, the AD conversion result is not affected, and therefore the gas concentration measurement is not affected.

[0045] Catalytic combustion alarms used in industrial settings operate within a temperature range of -40 to 70°C. Within this wide temperature range, the sensitivity of catalytic combustion sensors varies to some extent, but this effect can be eliminated through temperature compensation.

[0046] The microprocessor IC1 has a built-in temperature measurement function. Using this function, after detecting the current ambient temperature, based on the relationship between the sensor's sensitivity changes at different temperatures and room temperature of 25°C as tested in advance, the microprocessor IC1 can compensate for the sensitivity according to a pre-set program, thus eliminating the influence of temperature changes on gas concentration testing.

[0047] Different catalytic sensors (CG1) will have different output voltages even under identical conditions, such as the same power supply voltage, operating temperature, and applied gas concentration. This is due to the inherent discreteness of the sensors. During manufacturing, with the support of production tooling, a batch of sensor components is recorded in the same environment via serial port commands. The differential AD values ​​in clean air and at several fixed concentrations, such as 25% LEL, 50% LEL, and 75% LEL, are recorded separately.

[0048] Each sensor component can obtain a unique AD value corresponding to its concentration, which is only related to its own circuit and sensor characteristics. Even if there are differences in the data between different sensor components, it does not matter, as long as the AD value is within the allowable range.

[0049] This method eliminates the impact of sensor discreteness. By performing piecewise fitting on the acquired data, a data curve within the measurement range can be obtained. Then, during normal use, the corresponding gas concentration value can be calculated from the measured AD value, thus obtaining the digital processing result.

[0050] When the catalytic sensor CG1 is cold, its internal resistance is low, resulting in a large current consumption at the moment of power-on. As power is gradually applied, the internal resistance gradually increases, and the current decreases. Many industrial explosion-proof alarms connect to the controller via a bus. When the system powers on, the simultaneous power-on of numerous alarms can overload the power supply. To avoid this, a larger capacity power supply is typically used, but this results in unnecessary waste.

[0051] In a bus system, each alarm has a unique address number, facilitating bus inspection. Delaying power-on using this address number can prevent the aforementioned issues.

[0052] After microprocessor IC1 powers on, it controls the EN terminal of linear regulated power supply IC2 to shut off the power supply to the sensors. Microprocessor IC1 receives the local address number of the alarm via the serial port, uses this to generate different time delays, and then powers on the sensors. This ensures that the sensors in all alarms on the bus are powered on sequentially, avoiding concentrated power-on and thus reducing the impact on the power supply.

[0053] The cool-state current of the catalytic converter CG1 is approximately 1.5 to 2 times that of the hot-state current, with a normal power consumption of around 180mA and an initial power-on current of around 300mA. To avoid the power supply surge caused by simultaneous power-on of numerous sensors on the bus, a timeout delay is generated using the alarm's own address code, with a delay time of 0.2 seconds. For example, the sensor power supply for alarm at address 5 starts at 1 second; the sensor power supply for alarm at address 6 starts at 1.2 seconds.

[0054] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Any feature disclosed in this specification (including the abstract and drawings) may be replaced by other equivalent or similar features unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is only one example of a series of equivalent or similar features.

Claims

1. A digital processing circuit for a catalytic combustion sensor, characterized in that, include: Catalytic sensor CG1; The first detection resistor R1 is connected at one end to one end of the compensation element C inside the catalytic sensor CG1; The second detection resistor R2 has one end connected to one end of the detection element D inside the catalytic sensor CG1; the other end of the first detection resistor R1 is connected to the other end of the second detection resistor R2; and the other end of the compensation element C is connected to the other end of the detection element D. The microprocessor IC1 has a first input terminal connected to the connection terminal of the compensation element C and the other end of the detection element D, and a second input terminal connected to the connection terminal of the other end of the first detection resistor R1 and the second detection resistor R2. The wiring plug JP1 is connected to the microprocessor IC1 and is used for serial communication with external devices, and is powered by an external power source. A linear regulated power supply IC2 is connected to the wiring plug JP1 and is used to convert the power supply into a regulated power supply; the power output terminal of the linear regulated power supply IC2 is used to power the catalytic sensor CG1.

2. The digital processing circuit for a catalytic combustion sensor according to claim 1, characterized in that, The digital processing circuit also includes: The third resistor is connected in series between the first input terminal of the microprocessor IC1 and the connection terminal between the compensation element C and the other end of the detection element D; The fourth resistor is connected in series with the second input terminal of the microprocessor IC1 and the other end of the first detection resistor R1 and the second detection resistor R2.

3. The digital processing circuit for a catalytic combustion sensor according to claim 2, characterized in that, The digital processing circuit also includes: The fifth resistor R5 has one end connected to the control output terminal of the microprocessor IC1 and the other end connected to the control input terminal of the linear regulated power supply IC2; the microprocessor IC1 is used to control the on / off state of the linear regulated power supply IC2.

4. The digital processing circuit for a catalytic combustion sensor according to claim 3, characterized in that, The wiring plug JP1 includes an RXD terminal, a TXD terminal, a GND terminal, and a V33 terminal; the RXD terminal, TXD terminal, GND terminal, and V33 terminal are all connected to the microprocessor IC1. The RXD terminal and TXD terminal are used to output digital signals to the outside, and the V33 terminal is used to connect to an external power supply.

5. The digital processing circuit for a catalytic combustion sensor according to claim 4, characterized in that, The linear regulated power supply IC2 includes a Vin terminal, a Vout terminal, a GND terminal, and an EN terminal; the Vin terminal is connected to the V33 terminal of the connector JP1, the GND terminal is connected to the GND terminal of the connector JP1 and grounded, the Vout terminal is the power output terminal, and the EN terminal is the control input terminal.

6. The digital processing circuit for a catalytic combustion sensor according to claim 5, characterized in that, The Vout terminal of the linear regulated power supply IC2 is also connected to a capacitor C1, and the negative terminal of the capacitor C1 is grounded.

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