CN217787239U - High-precision resistance measuring device of resistance type gas sensor - Google Patents
High-precision resistance measuring device of resistance type gas sensor Download PDFInfo
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- CN217787239U CN217787239U CN202221566472.XU CN202221566472U CN217787239U CN 217787239 U CN217787239 U CN 217787239U CN 202221566472 U CN202221566472 U CN 202221566472U CN 217787239 U CN217787239 U CN 217787239U
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Abstract
The utility model relates to a resistance type gas sensor's high accuracy resistance measurement device, include: the constant current source, the resistance R1 that awaits measuring, precision resistance R2, voltage follower circuit, filter circuit, ADC circuit and main control circuit MCU, the constant current source is connected with the resistance R1 that awaits measuring, the resistance R1 and precision resistance R2 series connection await measuring, voltage follower circuit is all connected at the resistance R1 both ends that awaits measuring, voltage follower circuit connects filter circuit, filter circuit is connected with the ADC circuit, ADC circuit connection main control circuit MCU, voltage follower circuit is connected to precision resistance R2's one end, voltage follower circuit connects filter circuit, filter circuit is connected with the ADC circuit, ADC circuit connection main control circuit MCU. The measurement precision of the circuit is improved, and the circuit is simplified.
Description
Technical Field
The utility model relates to a sensor technical field, concretely relates to resistance type gas sensor's high accuracy resistance measurement device.
Background
The resistance type gas sensor is based on a sensor made of special materials, the resistance of the sensor is sensitive to the concentration of gas to be measured, the resistance value of the sensor generally changes linearly within a certain range and the concentration of the gas to be measured, but the change range of the resistance value is smaller, for example, a palladium-plated film hydrogen sensor, the change of the resistance value is generally within 20 ohms and corresponds to the hydrogen concentration of 0-50000 ppm, so that the main function of a sensor acquisition circuit is to accurately measure the resistance value of the sensor, the precision is +/-25 ppm, and the requirement on the measurement precision of the resistance value reaches 0.05 percent due to the large change range of parameters to be measured and the small change range of effective resistance.
SUMMERY OF THE UTILITY MODEL
The existing resistance value measurement adopts the Wheatstone bridge principle, a constant current source generates a fixed current to flow through a resistor to be measured, and then the voltage at two sides of the resistor is collected to reflect the resistance value to be measured. The method of measuring resistance by using the constant current source is applied to the measurement of the resistance sensor, but the conventional resistance measuring circuit cannot meet the precision requirement for the gas sensor, and the main reasons are as follows:
1. the Wheatstone bridge circuit has many components and parts, the accuracy of the resistance element is limited, and the measurement result error is easy to exceed the accuracy requirement after being influenced by the change of the environmental temperature.
2. The conventional constant current source has the problems of temperature drift and ripple, the precision cannot meet the precision requirement of the gas sensor, and the high-precision constant current source is expensive and is not suitable for the design requirement of the sensor.
An object of the utility model is to provide a resistance type gas sensor's high accuracy resistance measurement device, when it satisfies gas sensor resistance measurement accuracy requirement, the circuit is simple.
The utility model discloses a technical scheme is, a resistance type gas sensor's high accuracy resistance measurement device, include: the constant current source, the resistance R1 that awaits measuring, precision resistance R2, voltage follower circuit, filter circuit, ADC circuit and main control circuit MCU, the constant current source is connected with the resistance R1 that awaits measuring, the resistance R1 and precision resistance R2 series connection await measuring, voltage follower circuit is all connected at the resistance R1 both ends that awaits measuring, voltage follower circuit connects filter circuit, filter circuit is connected with the ADC circuit, ADC circuit connection main control circuit MCU, voltage follower circuit is connected to precision resistance R2's one end, voltage follower circuit connects filter circuit, filter circuit is connected with the ADC circuit, ADC circuit connection main control circuit MCU.
Further, the values of the resistance to be measured are: r1 = R2U 1/U2; in the formula: r1 and U1 are respectively a resistor to be tested and a voltage thereof; r2 and U2 are respectively a precision resistor and a voltage thereof.
Furthermore, one end of a resistor R4 is connected between the constant current source and the resistor R1 to be tested, the other end of the resistor R4 is connected with one end of a capacitor C1, the other end of the capacitor C1 is grounded, and the resistor R4 and the capacitor C1 form a filter circuit;
a first input end of the operational amplifier U5 is connected with the other end of the resistor R4, a second input end of the operational amplifier U5 is connected with one end of the resistor R7, an output end of the operational amplifier U5 is connected with the other end of the resistor R7, and the resistor R7 and the operational amplifier U5 form a voltage following circuit;
one end of the resistor R10 is connected with the output end of the operational amplifier U5, the other end of the resistor R10 is connected with one end of the capacitor C4, the other end of the capacitor C4 is grounded, and the resistor R10 and the capacitor C4 form a filter circuit.
Furthermore, one end of a resistor R5 is connected between the resistor R1 to be tested and the precision resistor R2, the other end of the resistor R5 is connected with one end of a capacitor C2, the other end of the capacitor C2 is grounded, and the resistor R5 and the capacitor C2 form a filter circuit;
a first input end of the operational amplifier U6 is connected with the other end of the resistor R5, a second input end of the operational amplifier U6 is connected with one end of the resistor R8, an output end of the operational amplifier U5 is connected with the other end of the resistor R8, and the resistor R8 and the operational amplifier U6 form a voltage following circuit;
one end of the resistor R11 is connected with the output end of the operational amplifier U6, the other end of the resistor R11 is connected with one end of the capacitor C5, the other end of the capacitor C5 is grounded, and the resistor R11 and the capacitor C5 form a filter circuit.
Furthermore, one end of a resistor R6 is connected between the resistor R3 to be tested and the precision resistor R2, the other end of the resistor R6 is connected with one end of a capacitor C3, the other end of the capacitor C3 is grounded, and the resistor R6 and the capacitor C3 form a filter circuit;
a first input end of the operational amplifier U7 is connected with the other end of the resistor R6, a second input end of the operational amplifier U7 is connected with one end of the resistor R9, an output end of the operational amplifier U7 is connected with the other end of the resistor R9, and the resistor R9 and the operational amplifier U7 form a voltage following circuit;
one end of the resistor R12 is connected with the output end of the operational amplifier U7, the other end of the resistor R21 is connected with one end of the capacitor C6, the other end of the capacitor C6 is grounded, and the resistor R12 and the capacitor C6 form a filter circuit.
Further, the precision resistor R2 is a precision resistor of 0.01%.
Compared with the prior art, the beneficial effects of the utility model are that:
1. the resistance to be measured is not affected by the precision of the constant current source, and a conventional constant current source with lower cost can be adopted.
2. The measuring precision of the circuit is improved by using the precision resistors connected in series, the number of discrete components of the bridge circuit can be saved, and the circuit is simplified.
3. The voltage follower circuit and the filter circuit improve the anti-interference capability of signals, and the resistors of the sensor to be tested and the precision resistors are arranged nearby to suppress common-mode interference.
Drawings
FIG. 1 is a schematic diagram of the overall circuit of the present invention;
fig. 2 is a schematic diagram of the overall circuit of the present invention.
Detailed Description
As shown in fig. 1, a high-precision resistance measuring apparatus of a resistance type gas sensor includes: the device comprises a constant current source, a resistor to be detected, a precision resistor, a voltage following circuit, a filter circuit, an ADC circuit and a main control circuit MCU.
The constant current source is connected with the resistor to be tested, the resistor to be tested is connected with the precise resistor in series, the two ends of the resistor to be tested are both connected with the voltage following circuit, the voltage following circuit is connected with the filter circuit, the filter circuit is connected with the ADC circuit, and the ADC circuit is connected with the MCU.
One end of the precision resistor is connected with a voltage following circuit, the voltage following circuit is connected with a filter circuit, the filter circuit is connected with an ADC circuit, and the ADC circuit is connected with a main control circuit MCU.
The calculation method of the resistance to be measured comprises the following steps:
R1 = R2*U1/U2；
in the formula: r1 and U1 are respectively a resistor to be tested and a voltage thereof; r2 and U2 are respectively a precision resistor and a voltage thereof.
As shown in fig. 2, one end of the resistor R4 is connected between the constant current source and the resistor R1 to be measured, the other end of the resistor R4 is connected to one end of the capacitor C1, the other end of the capacitor C1 is grounded, and the resistor R4 and the capacitor C1 form a filter circuit.
The first input end of the operational amplifier U5 is connected with the other end of the resistor R4, the second input end of the operational amplifier U5 is connected with one end of the resistor R7, the output end of the operational amplifier U5 is connected with the other end of the resistor R7, and the resistor R7 and the operational amplifier U5 form a voltage following circuit.
One end of the resistor R10 is connected with the output end of the operational amplifier U5, the other end of the resistor R10 is connected with one end of the capacitor C4, the other end of the capacitor C4 is grounded, and the resistor R10 and the capacitor C4 form a filter circuit.
One end of the resistor R5 is connected between the resistor R1 to be tested and the precision resistor R2, the other end of the resistor R5 is connected with one end of the capacitor C2, the other end of the capacitor C2 is grounded, and the resistor R5 and the capacitor C2 form a filter circuit.
The first input end of the operational amplifier U6 is connected with the other end of the resistor R5, the second input end of the operational amplifier U6 is connected with one end of the resistor R8, the output end of the operational amplifier U5 is connected with the other end of the resistor R8, and the resistor R8 and the operational amplifier U6 form a voltage following circuit.
One end of the resistor R11 is connected with the output end of the operational amplifier U6, the other end of the resistor R11 is connected with one end of the capacitor C5, the other end of the capacitor C5 is grounded, and the resistor R11 and the capacitor C5 form a filter circuit.
One end of the resistor R6 is connected between the resistor R3 to be tested and the precision resistor R2, the other end of the resistor R6 is connected with one end of the capacitor C3, the other end of the capacitor C3 is grounded, and the resistor R6 and the capacitor C3 form a filter circuit.
The first input end of the operational amplifier U7 is connected with the other end of the resistor R6, the second input end of the operational amplifier U7 is connected with one end of the resistor R9, the output end of the operational amplifier U7 is connected with the other end of the resistor R9, and the resistor R9 and the operational amplifier U7 form a voltage following circuit.
One end of the resistor R12 is connected with the output end of the operational amplifier U7, the other end of the resistor R21 is connected with one end of the capacitor C6, the other end of the capacitor C6 is grounded, and the resistor R12 and the capacitor C6 form a filter circuit.
The utility model discloses a measurement principle is: the constant current source supplies power to the resistors to be detected and the precision resistor which are connected in series, the voltages at the two ends of the two resistors are input into the ADC acquisition circuit after being filtered, amplified and filtered, and finally the resistance value to be detected is obtained through calculation of the main control circuit.
When the resistance R1 to be measured is calculated, the current precision and stability are not required, and therefore the influence of a constant current source on the measurement precision is eliminated. The change of the environmental temperature can cause the change of the precision resistor R2, and the precision resistor R2 is adopted, so that the requirement of improving the measurement precision of the circuit is met.
The voltage follower circuit and the filter circuit formed by the operational amplifier are utilized to achieve the purposes of improving the signal quality and inhibiting other signal interference.
The application also discloses a high-precision resistance measuring method for the resistance type gas sensor, which is characterized in that a resistance to be measured is connected with a 0.01% precision resistor in series, a constant current source is utilized for supplying power, the parameter change of an element is dynamically tracked, and calculation compensation is carried out, so that the requirement of the resistance measuring precision of the gas sensor is met, and meanwhile, a circuit is simple and the cost is not greatly increased.
The main idea is that the voltages at two ends of a resistor to be measured and a precision resistor reach the input end of an acquisition circuit through a voltage following circuit and a filter circuit; the main controller MCU utilizes two AD channels to respectively carry out voltage measurement, and then utilizes two voltage values to calculate the resistance value to be measured:
the resistance value of the precision resistor is not influenced by the change of the environmental temperature, and the change value of the constant current source current influenced by the temperature can be calculated reversely by measuring the voltage at the two ends of the precision resistor;
the resistance value of the sensor resistor is calculated based on the compensation of the change value of the current of the constant current source, and under the condition that the sensor resistor to be detected and the precision resistor are close to each other as much as possible, the noise interference in the process that signals pass through the circuit can be suppressed in a common mode.
The above, only be the embodiment of the preferred of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art is in the technical scope of the present invention, according to the technical solution of the present invention and the utility model, which are designed to be replaced or changed equally, all should be covered within the protection scope of the present invention.
Claims (6)
1. A high-precision resistance measuring device of a resistance type gas sensor is characterized in that: the method comprises the following steps: the constant current source, the resistance R1 that awaits measuring, precision resistance R2, voltage follower circuit, filter circuit, ADC circuit and main control circuit MCU, the constant current source is connected with the resistance R1 that awaits measuring, the resistance R1 and precision resistance R2 series connection await measuring, voltage follower circuit is all connected at the resistance R1 both ends that awaits measuring, voltage follower circuit connects filter circuit, filter circuit is connected with the ADC circuit, ADC circuit connection main control circuit MCU, voltage follower circuit is connected to precision resistance R2's one end, voltage follower circuit connects filter circuit, filter circuit is connected with the ADC circuit, ADC circuit connection main control circuit MCU.
2. The high-precision resistance measuring device according to claim 1, characterized in that: the values of the resistance to be measured are: r1 = R2U 1/U2; in the formula: r1 and U1 are respectively a resistor to be tested and a voltage thereof; r2 and U2 are respectively a precision resistor and a voltage thereof.
3. A high accuracy resistance measuring apparatus according to claim 2, wherein: one end of the resistor R4 is connected between the constant current source and the resistor R1 to be tested, the other end of the resistor R4 is connected with one end of the capacitor C1, the other end of the capacitor C1 is grounded, and the resistor R4 and the capacitor C1 form a filter circuit;
a first input end of the operational amplifier U5 is connected with the other end of the resistor R4, a second input end of the operational amplifier U5 is connected with one end of the resistor R7, an output end of the operational amplifier U5 is connected with the other end of the resistor R7, and the resistor R7 and the operational amplifier U5 form a voltage following circuit;
one end of the resistor R10 is connected with the output end of the operational amplifier U5, the other end of the resistor R10 is connected with one end of the capacitor C4, the other end of the capacitor C4 is grounded, and the resistor R10 and the capacitor C4 form a filter circuit.
4. A high-precision resistance measuring device according to claim 3, wherein: one end of the resistor R5 is connected between the resistor R1 to be tested and the precision resistor R2, the other end of the resistor R5 is connected with one end of the capacitor C2, the other end of the capacitor C2 is grounded, and the resistor R5 and the capacitor C2 form a filter circuit;
a first input end of the operational amplifier U6 is connected with the other end of the resistor R5, a second input end of the operational amplifier U6 is connected with one end of the resistor R8, an output end of the operational amplifier U5 is connected with the other end of the resistor R8, and the resistor R8 and the operational amplifier U6 form a voltage following circuit;
one end of the resistor R11 is connected with the output end of the operational amplifier U6, the other end of the resistor R11 is connected with one end of the capacitor C5, the other end of the capacitor C5 is grounded, and the resistor R11 and the capacitor C5 form a filter circuit.
5. The high-precision resistance measuring device according to claim 4, wherein: one end of the resistor R6 is connected between the resistor R3 to be tested and the precision resistor R2, the other end of the resistor R6 is connected with one end of the capacitor C3, the other end of the capacitor C3 is grounded, and the resistor R6 and the capacitor C3 form a filter circuit;
a first input end of the operational amplifier U7 is connected with the other end of the resistor R6, a second input end of the operational amplifier U7 is connected with one end of the resistor R9, an output end of the operational amplifier U7 is connected with the other end of the resistor R9, and the resistor R9 and the operational amplifier U7 form a voltage following circuit;
one end of the resistor R12 is connected with the output end of the operational amplifier U7, the other end of the resistor R21 is connected with one end of the capacitor C6, the other end of the capacitor C6 is grounded, and the resistor R12 and the capacitor C6 form a filter circuit.
6. The high-precision resistance measuring device according to claim 5, wherein: the precision resistor R2 is a precision resistor of 0.01%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202221566472.XU CN217787239U (en) | 2022-06-22 | 2022-06-22 | High-precision resistance measuring device of resistance type gas sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202221566472.XU CN217787239U (en) | 2022-06-22 | 2022-06-22 | High-precision resistance measuring device of resistance type gas sensor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN217787239U true CN217787239U (en) | 2022-11-11 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202221566472.XU Active CN217787239U (en) | 2022-06-22 | 2022-06-22 | High-precision resistance measuring device of resistance type gas sensor |
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| Country | Link |
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| CN (1) | CN217787239U (en) |
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2022
- 2022-06-22 CN CN202221566472.XU patent/CN217787239U/en active Active
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