Low temperature drift high precision thermal flow conversion circuit

Abstract

This invention relates to a low-temperature drift, high-precision heat flux conversion circuit, characterized by comprising: using two operational amplifiers U1A and U1B with identical parameters on the same substrate, whose temperature drifts are similar, and setting the two operational amplifiers to be in opposite directions to cancel out the effects of their offset voltages and temperature drifts, first forming a fully differential amplifier circuit to amplify the small signal from the heat flux sensor; the amplified signal is then passed through two other operational amplifiers U2A and U2B on the same substrate to form an additive bias circuit, obtaining a high-precision voltage signal V0 with adjustable bias, low temperature drift, and low offset. The beneficial effect of this invention is that it reduces the output offset voltage, thereby reducing the impact of input offset voltage and temperature drift on the accuracy of heat flux acquisition, and improving the accuracy of heat flux sampling.

Description

Technical Field

[0001] This invention relates to the field of heat flux sensor technology, specifically a low-temperature drift, high-precision heat flux conversion circuit. Background Technology

[0002] In recent years, the development of heat flux sensors has been rapid, with widespread applications in industrial production, theoretical research, aerospace, and engineering. However, temperature drift and offset voltage can significantly reduce the data acquisition accuracy and stability of the heat flux sensor due to signal conversion circuitry. To mitigate the impact of offset voltage and temperature drift in the sensor's signal conversion circuitry, temperature compensation circuits are typically used to correct these issues and minimize their influence on acquisition accuracy.

[0003] A search of existing papers on CNKI (China National Knowledge Infrastructure) revealed that the paper "Research on Heat Flow Sensor System" uses a single fully differential amplifier circuit to amplify the mV-level heat flow signal. This method cannot adjust the bias voltage, and after several hundred times signal amplification, it amplifies the effects of temperature drift and offset voltage. Commonly used heat flow processing circuits are as follows: Figure 2 As shown, Where R2 = R3 = R5 = R6, R1 = R4, and the upper limit of the output is changed by adjusting the value of R7. As shown in the formula above, the input consists of two parts: Vin, the heat flux signal, and Vref, the bias voltage. After being amplified several hundred times, the output is obtained. However, because the bias voltage is affected by temperature drift, the output error will be amplified several hundred times after amplification, reaching a maximum of about 0.2V. This, combined with the temperature drift of the op-amp itself, severely affects the output accuracy. Summary of the Invention

[0004] The purpose of this invention is to provide a low-temperature drift, high-precision heat flux conversion circuit, which aims to reduce the impact of temperature drift and offset voltage on the acquisition accuracy of the heat flux sensor.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] A low-temperature drift, high-precision heat flux conversion circuit, characterized by comprising:

[0007] The fully differential amplifier circuit uses two op-amps U1A and U1B with the same substrate parameters and similar temperature drift. The two op-amps are set to reverse to cancel out the effects of each other's offset voltage and temperature drift. This first forms a fully differential amplifier circuit to amplify the small signal from the heat flow sensor.

[0008] The bias circuit amplifies the signal, which is then passed through two other operational amplifiers, U2A and U2B, on the same substrate to form an additive bias circuit, resulting in a high-precision voltage signal V0 with adjustable bias, low temperature drift, and low offset.

[0009] A further technical solution is:

[0010] The fully differential amplifier circuit consists of operational amplifiers U1A and U1B, and resistors R1, R2, R3, R4, R5, R6, and R7. The non-inverting input of operational amplifier U1A is connected to resistors R1 and R2. The other end of R1 is connected to the positive potential terminal of the heat flow sensor. The other end of R2 is connected to resistors R3 and R7. The other end of R3 is connected to the output terminal of operational amplifier U1B. The other end of R7 is connected to resistors R5 and R6. The other end of R5 is connected to the non-inverting input of U1B and R4. The other end of R6 is grounded. The other end of R4 is connected to the negative potential terminal of the heat flow sensor. The output terminal of U1A is connected to the inverting input of U1A and the inverting input of U1B.

[0011] The bias circuit consists of operational amplifiers U2A and U2B, and resistors R8, R9, R10, R11, and R12. The non-inverting input of operational amplifier U2A is connected to resistors R8, R9, and R10. The other end of R8 is grounded. The other end of R9 is connected to the reference voltage Vref. The other end of R10 is connected to the output of operational amplifier U1B. The inverting input of operational amplifier U2A is connected to resistor R11, the inverting input of operational amplifier U2B, and the output. The other end of resistor R11 is grounded. The non-inverting input of operational amplifier U2B is connected to resistor R12. The other end of R12 is connected to the output of U2A. The output of U2A outputs the amplified voltage Vo.

[0012] In a fully differential amplifier circuit, resistors R2 = R3 = R5 = R6, and R1 = R4. The upper limit of the output is changed by adjusting the value of R7. Since R1, R2, and R7 are all of the same type, their temperature drift suppression can cancel each other out.

[0013] In the bias circuit, R9 = R10 = R12, R8 / / R9 / / R10 = R11 / / R12, thus obtaining the output VO = V ref +V1.

[0014] The beneficial effect of this invention is that it reduces the output offset voltage, thereby reducing the impact of the input offset voltage and temperature drift on the accuracy of heat flux acquisition and improving the accuracy of heat flux sampling. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating the principle of the present invention;

[0016] Figure 2 This is a commonly used heat flow processing circuit diagram in existing technology. Detailed Implementation

[0017] like Figure 1 As shown, the present invention provides a low-temperature drift high-precision heat flux conversion circuit, which includes two stages: the front stage is a small-signal fully differential amplifier circuit for a heat flux sensor, and the back stage is a bias circuit with adjustable bias.

[0018] More specifically, the fully differential amplifier circuit consists of operational amplifiers U1A and U1B, and resistors R1, R2, R3, R4, R5, R6, and R7;

[0019] The non-inverting input of op-amp U1A is connected to resistors R1 and R2. The other end of R1 is connected to the positive potential terminal of the heat flow sensor. The other end of R2 is connected to resistors R3 and R7. The other end of R3 is connected to the output terminal of op-amp U1B. The other end of R7 is connected to resistors R5 and R6. The other end of R5 is connected to the non-inverting input of U1B and R4. The other end of R6 is grounded. The other end of R4 is connected to the negative potential terminal of the heat flow sensor. The output terminal of U1A is connected to the inverting input of U1A and the inverting input of U1B.

[0020] The bias circuit consists of operational amplifiers U2A and U2B, and resistors R8, R9, R10, R11, and R12.

[0021] The non-inverting input of op-amp U2A is connected to resistors R8, R9, and R10. The other end of R8 is grounded, the other end of R9 is connected to the reference voltage Vref, and the other end of R10 is connected to the output of op-amp U1B. The inverting input of op-amp U2A is connected to resistor R11, the inverting input of op-amp U2B, and the output. The other end of resistor R11 is grounded. The non-inverting input of op-amp U2B is connected to resistor R12, the other end of which is connected to the output of U2A. The output of U2A outputs the amplified voltage Vo.

[0022] The working principle of this invention is as follows:

[0023] By using two operational amplifiers with identical parameters on the same substrate and similar temperature drift, the heat flow sensor is configured with the two operational amplifiers in opposite directions to cancel out the effects of their offset voltage and temperature drift. A fully differential amplifier circuit is first constructed. The thermoelectric potential caused by temperature changes is amplified by several hundred times by the fully differential operational amplifier circuit. The amplified heat flow signal is then conditioned by an additive bias circuit composed of two other operational amplifiers on the same substrate to obtain a high-precision voltage signal with low temperature drift and low offset that has an adjustable bias and meets the required voltage range.

[0024] The specific principle is as follows: Figure 1 As shown, the millivolt-level voltage signal output by the heat flux sensor passes through a fully differential operational amplifier circuit, the output of which is... In this circuit, resistors R2 = R3 = R5 = R6, and R1 = R4. The upper limit of the output is changed by adjusting the value of R7. Since R1, R2, and R7 are all of the same type, temperature drift suppression can cancel each other out, so the circuit output voltage V1 is minimally affected by temperature drift. Furthermore, by using two operational amplifiers with identical parameters on the same substrate for the heat flow sensor, their temperature drifts are similar. Setting the two operational amplifiers to be in opposite directions further cancels out the effects of their offset voltage and temperature drift. Where V refThe bias voltage is used to adjust the lower limit of the output, while satisfying R9=R10=R12, R8 / / R9 / / R10=R11 / / R12, thus obtaining the output VO=V. ref +V1 indicates that the output signal consists of the bias voltage and the amplified thermal flux voltage signal. Since the temperature drift of R9, R10, and R12 is consistent, and the bias circuit is composed of two operational amplifiers on the same substrate with similar temperature drifts, setting the two operational amplifiers to inverse polarity further cancels out the effects of their offset voltages and temperature drifts. This results in a high-precision voltage signal with low temperature drift and low offset, where the bias is adjustable and the required voltage range is met.

Claims

1. A low-temperature drift, high-precision heat flux conversion circuit, characterized in that... include: The fully differential amplifier circuit uses two op-amps U1A and U1B with the same substrate parameters and similar temperature drift. The two op-amps are set to reverse to cancel out the effects of each other's offset voltage and temperature drift. This first forms a fully differential amplifier circuit to amplify the small signal from the heat flow sensor. The bias circuit amplifies the signal, which is then passed through two other op-amps, U2A and U2B, on the same substrate to form an additive bias circuit, resulting in a high-precision voltage signal VO with adjustable bias, low temperature drift, and low offset. The fully differential amplifier circuit consists of operational amplifiers U1A and U1B, and resistors R1, R2, R3, R4, R5, R6, and R7. The non-inverting input of operational amplifier U1A is connected to resistors R1 and R2. The other end of R1 is connected to the positive potential terminal of the heat flow sensor. The other end of R2 is connected to resistors R3 and R7. The other end of R3 is connected to the output terminal of operational amplifier U1B. The other end of R7 is connected to resistors R5 and R6. The other end of R5 is connected to the non-inverting input of U1B and R4. The other end of R6 is grounded. The other end of R4 is connected to the negative potential terminal of the heat flow sensor. The output terminal of U1A is connected to the inverting input of U1A and the inverting input of U1B. The bias circuit consists of operational amplifiers U2A and U2B, and resistors R8, R9, R10, R11, and R12. The non-inverting input of operational amplifier U2A is connected to resistors R8, R9, and R10. The other end of R8 is grounded, and the other end of R9 is connected to the reference voltage V. ref The other end of R10 is connected to the output terminal of op-amp U1B. The inverting terminal of op-amp U2A is connected to resistor R11, the inverting terminal of op-amp U2B and the output terminal. The other end of resistor R11 is grounded. The non-inverting terminal of op-amp U2B is connected to resistor R12. The other end of R12 is connected to the output terminal of U2A. The output terminal of U2A outputs the amplified voltage VO. In the fully differential amplifier circuit, resistors R2 = R3 = R5 = R6, R1 = R4, and the upper limit of the output is changed by adjusting the value of R7. Since R1, R2, and R7 are selected as resistors of the same type, temperature drift is suppressed and canceled out. In the bias circuit, R9 = R10 = R12, R8 / / R9 / / R10 = R11 / / R12, and the output terminal of U1B outputs V1, thus obtaining the output VO = V ref +V1.

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