A platinum resistance temperature sensor demodulation circuit

Abstract

The application discloses a platinum resistance temperature sensor demodulation circuit, which comprises an excitation circuit, a platinum resistance signal conversion circuit, an amplification circuit and a compensation circuit; the excitation circuit excites the supply voltage of the platinum resistance signal conversion circuit; the amplification circuit amplifies and processes the output voltage signal of the platinum resistance signal conversion circuit; and the compensation circuit proportionally feeds back the output signal of the amplification circuit to the excitation circuit, so that the voltage output by the excitation circuit changes with the change of the measured temperature, thereby compensating the output signal. The application compensates the output signal of the platinum resistance, and the temperature measurement precision of the platinum resistance temperature sensor is higher.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of airborne sensors, and relates to a platinum resistance temperature sensor demodulation circuit. BACKGROUND

[0002] In an aircraft parameter measurement system, the temperature of gas or liquid in a pipeline often needs to be measured, and currently, the most commonly used way is to detect by using a platinum resistance temperature measurement principle. According to the standard characteristic curve of the platinum resistance in IEC 60751: R t =R0[1+At+Bt 2 +C(t-100)t 3 ](-200℃<t<0℃), R t =R0(1+At+Bt 2 )(0℃<t<850℃), in the formula, R t is the resistance value of the platinum resistance at temperature t, R0 is the resistance value of the platinum resistance at temperature t=0℃, A=3.9083×10 -3 ℃ -1 , B=-5.775×10 -7 ℃ -2 , and C=-4.183×10 -12 ℃ -4 . It can be seen that the output resistance of the platinum resistance is not linear with the temperature, and when the measurement temperature range is (-55-150)℃, the nonlinearity can reach 0.77%, and when the measurement temperature range is wider, the nonlinearity is larger, and obviously, the 0.5% precision requirement required by the control system cannot be met. Therefore, the output signal of the platinum resistance must be compensated and demodulated.

[0003] The existing technology often adopts the mode as described in the invention of CN 111122170 B: first, the resistance signal is converted into a voltage signal, the amplified voltage signal is collected and converted into a digital signal through analog-digital conversion after amplification, and then the platinum resistance is compensated for nonlinearity through a software algorithm in the CPU. This mode can well solve the nonlinearity problem of the platinum resistance by selecting a suitable calibration method, but the calibration workload is large, and calibration at more than 5 temperature points is often required to obtain an accurate calculation model, at the same time, this also makes the software algorithm complex, and the time cost and economic cost are large. In addition, this scheme uses more electronic components and has a large circuit size, which is not conducive to the miniaturization of the sensor. SUMMARY

[0004] The purpose of the application is to provide a platinum resistance temperature sensor demodulation circuit. The application compensates for the output signal of the platinum resistance, so that the temperature measurement accuracy of the platinum resistance temperature sensor is higher.

[0005] The technical scheme of the present application is: a platinum resistance temperature sensor demodulation circuit, comprising an excitation circuit, a platinum resistance signal conversion circuit, an amplification circuit and a compensation circuit; the excitation circuit excites the platinum resistance signal conversion circuit with a power supply voltage; the amplification circuit amplifies the output voltage signal of the platinum resistance signal conversion circuit; and the compensation circuit feeds back the output signal of the amplification circuit to the excitation circuit in proportion, so that the voltage output by the excitation circuit changes with the measured temperature, thereby compensating the output signal.

[0006] In the aforementioned platinum resistance temperature sensor demodulation circuit, the excitation circuit comprises a voltage reference U1, an operational amplifier U2, resistors Rf, R8-R10; the output voltage of the voltage reference U1 is V ref ; the output end of the voltage reference U1 is connected to one end of the resistor R9, and the other end of the resistor R9 is connected to the same direction input end of the operational amplifier U2; one end of the resistor R10 is connected to the ground potential, and the other end is connected to the negative direction input end of the operational amplifier U2; one end of the resistor Rf is connected to the negative direction input end of the operational amplifier U2, and the other end is connected to the output end of the operational amplifier U2; and the excitation circuit is used to provide an excitation voltage for the subsequent platinum resistance conversion circuit.

[0007] In the aforementioned platinum resistance temperature sensor demodulation circuit, the platinum resistance signal conversion circuit comprises resistors R1-R5 and a platinum resistance R t ; one end of the resistor R1 is connected to the first end of the resistor R3, and the other end is connected to the first end of the resistor R2; the second end of the resistor R2 is connected to the first end of the platinum resistance R t , and is connected to the ground potential; the resistors R4 and R5 are connected in parallel to form a common first end and a common second end; the common first end of the resistors R4 and R5 is connected to the second end of the platinum resistance R t , and the common second end of the resistors R4 and R5 is connected to the second end of the resistor R3; the common end of the resistors R3 and R1 is connected to the output end of the U2 in the excitation circuit; and the circuit is mainly used to convert the temperature-related resistance into a weak temperature-related voltage signal.

[0008] In the aforementioned platinum resistance temperature sensor demodulation circuit, the amplification circuit comprises an instrument operational amplifier U3, a resistor Rg and a bias voltage V off ; the two ends of the resistor Rg are connected to the gain setting ends of the instrument operational amplifier U3; the same direction input end of the instrument operational amplifier U3 is connected to the second end of the resistor R3 in the aforementioned platinum resistance signal conversion circuit, and the reverse direction input end of the instrument operational amplifier U3 is connected to the common end of the resistor R1 and the resistor R2 in the aforementioned platinum resistance signal conversion circuit; the bias voltage V off is connected to the bias setting pin of the instrument operational amplifier U3; and the circuit is mainly used to amplify the weak temperature-related voltage signal.

[0009] The foregoing platinum resistance temperature sensor demodulation circuit, the compensation circuit comprises resistors R6 and R7; one end of the resistor R6 is connected to the output end of the amplification circuit, and the other end is connected to the first end of the resistor R7; the second end of the resistor R7 is connected to the ground potential; the circuit is mainly used to feed back the output signal to the excitation circuit, so that the voltage at the output end of U2 in the excitation circuit changes, and then the final output signal of the sensor is adjusted.

[0010] The foregoing platinum resistance temperature sensor demodulation circuit, the common end of the resistor R6 and the resistor R7 is connected to the same direction input end of the operational amplifier U2 through the resistor R8.

[0011] The foregoing platinum resistance temperature sensor demodulation circuit, the resistance value of the resistor R10 is equal to the resistance value of the resistor Rf.

[0012] The foregoing platinum resistance temperature sensor demodulation circuit, the resistance values of the resistors R1-R4 are equal, and the resistance value of R4 in parallel with R5 plus the resistance value of the platinum resistance Rt at the lower limit of the measured temperature is equal to the resistance value of the resistor R2.

[0013] The foregoing platinum resistance temperature sensor demodulation circuit, the circuit satisfies the following formula:

[0014]

[0015] Wherein, G is the amplification multiple generated by connecting the resistor Rg to the instrument operational amplifier U3, and k=R7 / (R6+R7).

[0016] The advantages of the present application are: compared with the prior art, the demodulation circuit described in the present application realizes high-precision demodulation of the platinum resistance temperature sensor with fewer electronic components, without using AD conversion circuit and CPU acquisition algorithm circuit, so that the volume of the entire sensor is smaller. The debugging method of the circuit is simple and easy to implement, and only needs to be calibrated at the upper limit temperature, the lower limit temperature and the intermediate point temperature, which reduces more than two temperature points compared with the debugging of the previous circuit, thereby shortening the debugging period of the sensor. BRIEF DESCRIPTION OF DRAWINGS

[0017] Fig. 1 It is a principle block diagram representing the present application;

[0018] Fig. 2 It is a circuit principle diagram representing the present application;

[0019] Fig. 3 It is a three-wire connection method of the platinum resistance connection circuit. DETAILED DESCRIPTION

[0020] The present application will be further described below in combination with the drawings and examples, but it is not used as the basis for limiting the present application.

[0021] Embodiment 1. A platinum resistance temperature sensor demodulation circuit, as shown in Figs. 1-3 by feeding back the final output signal of the sensor to the excitation circuit in proportion, the power supply to the platinum resistance bridge is changed with the measured temperature, so as to offset the nonlinear change of the platinum resistance bridge with temperature, thereby reducing the linearity of the final output signal of the sensor, so that the accuracy of the platinum resistance temperature sensor is improved.

[0022] The demodulation circuit comprises an excitation circuit, a platinum resistance signal conversion circuit, an amplification circuit and a compensation circuit, so that the corresponding output of the platinum resistance temperature sensor is (0.5-4.5) V when the temperature measurement range is (-55-155) ℃.

[0023] The excitation circuit comprises a voltage reference U1, an operational amplifier U2, resistors Rf, R8-R10. The output terminal of the voltage reference U1 is connected to one end of the resistor R9, the other end of the resistor R9 is connected to the same input terminal of the operational amplifier U2, and the first end of the resistor R8 is connected to the same input terminal of the operational amplifier U2; one end of the resistor R10 is connected to the ground potential, and the other end is connected to the negative input terminal of the operational amplifier U2; one end of the resistor Rf is connected to the negative input terminal of the operational amplifier U2, and the other end is connected to the output terminal of the operational amplifier U2. The excitation circuit is mainly used to provide excitation voltage for the subsequent platinum resistance conversion circuit.

[0024] The output voltage V ref of the voltage reference U1 is 5V, and the resistance values of the resistors R10 and Rf are both 100K.

[0025] The platinum resistance signal conversion circuit comprises resistors R1-R5, a platinum resistance Rt t . One end of the resistor R1 is connected to the first end of the resistor R3, and the other end is connected to the first end of the resistor R2. The second end of the resistor R2 is connected to the first end of the platinum resistance Rt t , and is connected to the ground potential. The resistors R4 and R5 are connected in parallel to form a common first end and a common second end. The common first end of the resistors R4 and R5 is connected to the second end of the platinum resistance Rt t , and the common second end of the resistors R4 and R5 is connected to the second end of the resistor R3. The common end of the resistors R3 and R1 is connected to the output terminal of the U2 in the excitation circuit. This circuit is mainly used to convert the temperature-dependent resistance into a weak temperature-dependent voltage signal.

[0026] The resistance values of the resistors R1-R4 are all 3K, and the resistance value of the resistor R5 is 111K.

[0027] Optionally, the connection mode of the platinum resistance Rt to the circuit can refer to the three-wire connection method shown in Fig. 3 .

[0028] The amplification circuit comprises an instrument operational amplifier U3, a resistor Rg, a bias voltage Voff The two ends of the resistance Rg are connected to the two ends of the gain setting of the instrument operational amplifier U3. The same direction input end of the instrument operational amplifier U3 is connected to the second end of the resistance R3 in the platinum resistance signal conversion circuit, and the reverse input end of the instrument operational amplifier U3 is connected to the common end of the resistance R1 and the resistance R2 in the platinum resistance signal conversion circuit. The bias voltage V off The bias setting pin of the instrument operational amplifier U3 is connected. off Here, it is 0.5V. The circuit is mainly used for amplifying the weak voltage signal related to temperature.

[0029] The compensation circuit includes the resistance R6 and the resistance R7. One end of the resistance R6 is connected to the output end of the amplification circuit, and the other end is connected to the first end of the resistance R7. The second end of the resistance R7 is connected to the ground potential. The common end of the resistance R6 and the resistance R7 is connected to the second end of the resistance R8 in the excitation circuit. The resistance R8 is 200K, and the resistance R9 is 300K. The circuit is mainly used for feeding back the output signal to the excitation circuit, so that the output end voltage of U2 in the excitation circuit changes, and then the final output signal of the sensor is adjusted.

[0030] In the circuit, the following formula is established:

[0031]

[0032] Wherein, G is the amplification multiple generated by connecting the resistance Rg to the instrument operational amplifier U3, and k=R7 / (R6+R7).

[0033] According to formula (1), the following formula is established:

[0034]

[0035] It can be known from the temperature measurement range and the corresponding output relationship of the platinum resistance temperature sensor that when the temperature t is 155℃, that is, Rt=159.19Ω, Vout=4.5V; when the temperature t is 50℃, that is, Rt=119.4Ω, Vout=2.5V.

[0036] The Rt and Vout under the above two groups of temperature values are substituted into formula (2) respectively, so that G=146.556 and K=0.025 can be obtained.

[0037] That is, R7=1K and R6=39K can make the output generated by the circuit meet the requirements.

[0038] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any changes or replacements that can be easily thought of by those skilled in the art within the scope disclosed by the present application should be covered within the protection scope of the present application.

Claims

1. A demodulation circuit for a platinum resistance temperature sensor, characterized in that, It includes an excitation circuit, a platinum resistance signal conversion circuit, an amplification circuit, and a compensation circuit. The excitation circuit provides the power supply voltage to the platinum resistance signal conversion circuit. The amplification circuit amplifies the output voltage signal of the platinum resistance signal conversion circuit. The compensation circuit feeds back the output signal of the amplification circuit to the excitation circuit proportionally, so that the voltage output of the excitation circuit changes with the measured temperature, thereby compensating for the output signal. The excitation circuit includes a voltage reference U1, an operational amplifier U2, a resistor Rf, and resistors R8 to R10; the output voltage of the voltage reference U1 is V. ref The output terminal of U1 is connected to one end of resistor R9, and the other end of resistor R9 is connected to the non-inverting input terminal of operational amplifier U2; one end of resistor R10 is connected to ground potential, and the other end is connected to the negative input terminal of operational amplifier U2; one end of resistor Rf is connected to the negative input terminal of operational amplifier U2, and the other end is connected to the output terminal of operational amplifier U2. The platinum resistance signal conversion circuit includes resistors R1 to R5 and a platinum resistance resistor R. t One end of resistor R1 is connected to the first end of resistor R3, and the other end is connected to the first end of resistor R2; the second end of resistor R2 is connected to the platinum resistance resistor R... t The first terminal of the resistor is connected to ground potential; resistors R4 and R5 are connected in parallel to form a common first terminal and a common second terminal; the common first terminal of resistors R4 and R5 is connected to the platinum resistance resistor R. t The second terminal of resistors R4 and R5 is connected to the second terminal of resistor R3; the common second terminal of resistors R3 and R1 is connected to the output terminal of U2 in the above excitation circuit. The amplifier circuit includes instrumentation amplifier U3, resistor Rg, and bias voltage V. off The two ends of resistor Rg are respectively connected to the gain setting terminals of instrumentation operational amplifier U3; the non-inverting input terminal of instrumentation operational amplifier U3 is connected to the second terminal of resistor R3 in the above-mentioned platinum resistance signal conversion circuit, and the inverting input terminal of instrumentation operational amplifier U3 is connected to the common terminal of resistors R1 and R2 in the above-mentioned platinum resistance signal conversion circuit; bias voltage V off Connect the bias setting pin of the instrument operational amplifier U3; The compensation circuit includes resistors R6 and R7; one end of resistor R6 is connected to the output terminal of the amplifier circuit, and the other end is connected to the first terminal of resistor R7; the second terminal of resistor R7 is connected to ground potential. The common terminal of resistors R6 and R7 is connected to the non-inverting input terminal of operational amplifier U2 via resistor R8.

2. The demodulation circuit for the platinum resistance temperature sensor according to claim 1, characterized in that, The resistance values ​​of resistor R10 and resistor Rf are equal.

3. The demodulation circuit for the platinum resistance temperature sensor according to claim 1, characterized in that, The resistances of resistors R1 through R4 are equal. The resistance of R4 and R5 in parallel is added to the resistance of the platinum resistance R at the lower limit of the measurement temperature. t The resistance of is equal to the resistance of resistor R2.

Images