CN201464071U - A high-precision temperature measuring device using platinum resistance measurement - Google Patents

Abstract

The utility model provides a high-accuracy temperature measuring device by using a platinum resistor for measurement, comprising a low-drift voltage reference circuit part, a measurement isolation circuit part, a platinum resistor temperature sensor and a precision meter amplifying circuit part, wherein the low-drift voltage reference circuit part consists of a high-accuracy voltage reference and a fine-tuning sliding rheostat, and is used for providing low-drift reference voltage for the measurement isolation circuit part; the measurement isolation circuit part consists of a high-accuracy amplifier and a precision resistor, and is used for providing a constant flow source for the platinum resistor temperature sensor; a four-wire connection method is adopted by the platinum resistor temperature sensor, two of the wires are connected with the measurement isolation circuit part and taken as power leads, and other two wires are connected with the precision meter amplifying circuit part and taken as sensing leads; the precision meter amplifying circuit part consists of a precision meter amplifier and the precision resistor; and the gain of the precision meter amplifier is controlled by changing the resistance value of the precision resistor. By adopting the precision meter amplifier, the high-accuracy temperature measuring device can realize high-accuracy four-wire system temperature measurement for the platinum resistor temperature sensor, thus being applicable to the precise temperature measuring field with low cost, high accuracy as well as good stability and consistency.

Description

A high-precision temperature measuring device using platinum resistance measurement

technical field

The utility model relates to a temperature measuring device, in particular to a high-precision temperature measuring device which uses a platinum resistor to measure the temperature of a four-wire system.

Background technique

The platinum resistance temperature sensor uses the physical characteristic that the resistance value of platinum metal will change with the temperature. It has good reproducibility and stability, and the temperature range is wide, which can reach -200～ 650°C, widely used in the field of industrial temperature measurement and aerospace precision temperature measurement, and is made into a standard thermometer for measurement and calibration. Therefore, the temperature measurement device of the platinum resistance temperature sensor is required to have high precision, high stability and multiple Road consistency and other characteristics.

At present, most platinum resistance temperature measuring devices use two-wire unbalanced bridge technology and are powered by a voltage source. The disadvantage of using this two-wire temperature measurement method is that the voltage at both ends of the platinum resistance and the lead voltage connected to the platinum resistance constitute the output voltage value of the platinum resistance temperature sensor. The additional error caused by the wire resistance makes the actual measured voltage value Therefore, the wire of the measuring device should not be too long, and it can only be used in occasions where the accuracy of temperature measurement is not high.

At present, an improved platinum resistance temperature measuring device adopts the three-wire unbalanced bridge technology. The platinum resistance is used as a bridge arm resistance of the bridge. One lead wire is connected to the voltage measuring device, which eliminates the measurement error caused by lead resistance, but the bridge must be a full equi-arm bridge, and the cross-sectional area and length of the three wires drawn out are the same, otherwise the wire resistance will not be completely eliminated Impact.

At present, another improved platinum resistance temperature measuring device adopts four-wire measurement technology. The two leads of the platinum resistance provide constant current, and the voltage drop across the two ends of the platinum resistance is measured through the other two leads. The single-bipolar conversion amplifier realizes the voltage measurement across the platinum resistor. This method completely eliminates the error caused by the lead wire of the platinum resistor, but the disadvantage is that the cascade connection of three amplifiers makes the measurement accuracy difficult to control, increases the input voltage offset and input noise, and uses three precision operational amplifiers to increase the circuit Cost and circuit area, and multi-channel consistency is not good.

Contents of the invention

In order to solve the problems existing in the above-mentioned three common temperature measuring devices, the purpose of this utility model is to provide a high-precision temperature measuring device using platinum resistance measurement. It is suitable for precision temperature measurement with low cost, high precision, good stability and consistency.

In order to achieve the above purpose, the utility model provides a high-precision temperature measuring device using platinum resistance measurement, including: a low-drift voltage reference circuit part, a measurement isolation circuit part, a platinum resistance temperature sensor and a precision instrument amplifier circuit part.

The low-drift voltage reference circuit part is composed of a high-precision voltage reference and a fine-tuning sliding rheostat, which provides a low-drift reference voltage for the measurement isolation circuit part, and the voltage drift is lower than 10×10 ^-6 /°C;

The measurement isolation circuit part is composed of a high-gain high-precision amplifier and a precision resistor with a compensation voltage close to zero, and is used to provide a constant current source for the platinum resistance temperature sensor;

The platinum resistance temperature sensor adopts a four-wire connection method, wherein two lead resistances are connected to the measurement isolation circuit part as power leads, and the other two lead resistances are connected to the precision instrument amplifying circuit part as sensing leads;

The precision instrument amplifier circuit part is composed of a precision instrument amplifier and a precision resistor. The two sensing leads of the platinum resistance temperature sensor are connected to the precision instrument amplifier, and the precision instrument amplifier can be controlled by changing the resistance value of the precision resistor. gain. Here, the input impedance of the precision instrumentation amplifier is required to be high enough to ensure that no current flows through the input terminal.

When the high-precision temperature measuring device using platinum resistance measurement of the utility model is used for measurement, firstly, after connecting the low-drift voltage reference circuit part, the measurement isolation circuit part, the platinum resistance temperature sensor and the precision instrument amplification circuit part, the measurement constitutes the The precision instrument amplifier voltage output voltage Vout of the precision instrument amplifier circuit part; then, according to the gain G of the precision instrument amplifier, calculate the voltage at both ends of the platinum resistance temperature sensor: V=Vout/G; then, calculate by Ohm's law The resistance value of the platinum resistance temperature sensor Rt=V/I, wherein, I is the constant current source current, and then the precise temperature value is obtained by querying the resistance value of the platinum resistance temperature sensor and the temperature scale.

Here, since the platinum resistance temperature sensor is connected in series with the constant current source through two power leads, the current is constant, so the resistance value of the platinum resistance temperature sensor can be obtained through Ohm's law, and because the resistance value of the platinum resistance temperature sensor changes with temperature The precise temperature value can be obtained by querying the relationship between the resistance value and temperature of the platinum resistance temperature sensor.

The beneficial effect of the high-precision temperature measuring device using platinum resistance measurement of the utility model is that it is suitable for the field of precision temperature measurement with low cost, high precision, good stability and consistency. In order to meet the needs of various aspects, the optimized and improved design of the three general-purpose temperature measurement devices is realized. The high-precision four-wire temperature measurement of the platinum resistance temperature sensor is realized through the precision instrumentation amplifier, which makes the temperature measurement device more accurate. , stability and multi-channel consistency are better, and the cost is reduced, and the application range is wider.

Description of drawings

Fig. 1 is a block diagram of a high-precision temperature measuring device utilizing platinum resistance measurement of the present invention.

Fig. 2 is a schematic diagram of the electric connection of the high-precision temperature measuring device measured by platinum resistance of the present invention.

Fig. 3 is a measurement flowchart of the high-precision temperature measuring device using platinum resistance measurement of the present invention.

Detailed ways

A high-precision temperature measuring device of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a block diagram showing the composition of a high-precision temperature measuring device utilizing platinum resistance measurement of the present invention. As shown in Figure 1, the high-precision temperature measuring device using platinum resistance measurement of the utility model is mainly composed of a low-drift voltage reference circuit part, a measurement isolation circuit part, a platinum resistance temperature sensor and a precision instrument amplifier circuit part.

The low-drift voltage reference circuit part is composed of a high-precision voltage reference and a fine-tuning sliding rheostat, which provides a low-drift reference voltage for the measurement isolation circuit;

The measurement isolation circuit part is composed of a high-precision amplifier with high gain and close to zero compensation voltage and a precision resistor, which is used to provide a constant current source for the platinum resistance temperature sensor;

The platinum resistance temperature sensor adopts a four-wire connection method, wherein two lead resistances are connected to the measurement isolation circuit as power leads, and the other two lead resistances are connected to the precision instrument amplifier circuit as sensing leads.

The precision instrument amplifier circuit part is composed of a precision instrument amplifier and a precision resistor. Connect the two sensing leads of the platinum resistance temperature sensor to the precision instrument amplifier. By changing the resistance value of the precision resistor, the gain of the precision instrument amplifier can be controlled. Here, the input impedance of the precision instrumentation amplifier is required to be high enough to ensure that no current flows through the input.

Fig. 2 is a schematic diagram of the electrical connection of a high-precision temperature measuring device using platinum resistance measurement that constitutes the utility model. As shown in Figure 2, the low-drift voltage reference circuit is composed of a high-precision voltage reference and a fine-tuning sliding rheostat to ensure that the voltage drift does not exceed 10×10 ^-6 /°C. The measurement isolation circuit part is composed of a high-gain high-precision amplifier with a compensation voltage close to zero and precision resistors R1 and R2. The low-drift voltage reference circuit and the measurement isolation circuit together provide a constant current source for the platinum resistance temperature sensor Rt.

In addition, the high-precision temperature measuring device using platinum resistance measurement adopts four-wire platinum resistance temperature measurement, and Rx1, RX2, Rx3, and Rx4 are the four lead resistances of the platinum resistance temperature sensor, among which Rx1 and Rx3 belong to the power leads, Responsible for connecting the platinum resistance temperature sensor to the constant current source, Rx2 and Rx4 belong to the sense leads, responsible for connecting the voltage of the resistance temperature detector to the precision instrumentation amplifier. In this way, the constant current power supply responsible for driving the platinum resistance temperature sensor and the temperature measurement circuit can be separated. Since the input impedance of the precision instrument amplifier is high enough, that is, there is no current flowing through the input terminal, the voltage at both ends of A and B is the platinum resistance. The voltage across the temperature sensor Rt has nothing to do with the lead resistances Rx2 and Rx4, even if there is a voltage drop in the Rx1 and Rx3 lead resistances, it will not affect the accuracy of the measured voltage, and the temperature measurement accuracy is below 0.1°C.

倍，因此，本实用新型采用精密仪表放大器对铂电阻两端电压进行测量放大，不仅节省了器件，减小了电路面积，而且节约了电路成本。The precision instrument amplifier circuit part is composed of a precision instrument amplifier and a precision resistor Rg. By changing the resistance value of the precision resistor Rg, the gain of the precision instrument amplifier can be controlled. The reason why the utility model adopts a precision instrument amplifier circuit to replace the combination of an existing differential amplifier circuit and a single-bipolar conversion amplifier is mainly because the precision of the basic differential amplifier circuit is relatively poor, and the differential amplifier circuit is changing the amplification gain. When , it is necessary to adjust the resistance of the two differential amplifiers at the same time, making its accuracy difficult to control. At the same time, in the existing amplifying circuit composed of three amplifiers, since the output of the two differential amplifiers is used as the input of the subsequent unipolar conversion amplifier, the input voltage offset and input noise are the losses of the precision instrumentation amplifier.

times, therefore, the utility model uses a precision instrument amplifier to measure and amplify the voltage at both ends of the platinum resistor, which not only saves devices, reduces the circuit area, but also saves the circuit cost.

In addition, Fig. 3 is the measurement flowchart of the high-precision temperature measuring device utilizing platinum resistance measurement of the present invention, as shown in Figure 3, when the high-precision temperature measuring device utilizing platinum resistance measurement of the present invention is measuring, at first After connecting the low-drift voltage reference circuit part, the measurement isolation circuit part, the platinum resistance temperature sensor and the precision instrument amplifier circuit part, measure the precision instrument amplifier voltage output voltage Vout that constitutes the precision instrument amplifier circuit part; then, according to the Describe the gain G of the precision instrument amplifier, and calculate the voltage at both ends of the platinum resistance temperature sensor: V=Vout/G; then, calculate the resistance value Rt=V/I of the platinum resistance temperature sensor through Ohm's law, where I is a constant current Source current, and then obtain the precise temperature value by querying the relationship between the resistance value and temperature of the platinum resistance temperature sensor.

Here, since the platinum resistance temperature sensor is connected in series with the constant current source through two power leads, the current is constant, so the resistance value of the platinum resistance temperature sensor can be obtained through Ohm's law, and because the resistance value of the platinum resistance temperature sensor changes with temperature The precise temperature value can be obtained by querying the relationship between the resistance value and temperature of the platinum resistance temperature sensor.

In summary, the high-precision temperature measuring device using platinum resistance measurement of the utility model not only overcomes the measurement error caused by the lead wire resistance in the previous two-wire and three-wire unbalanced bridge circuits, but also makes up for the self-made differential The precision control difficulty, input voltage offset and large input noise caused by the cascade connection of the amplifier circuit and the double-click conversion amplifier have defects. The utility model uses a precision instrument amplifier circuit to measure the temperature of the platinum resistance temperature sensor in a four-wire system, and has higher Accuracy, better stability and multi-channel consistency, it is an innovative and optimally designed temperature measurement device, which meets the needs of high-precision temperature measurement and is widely used.

Claims (3)

1. A high-precision temperature measuring device utilizing platinum resistance measurement, is characterized in that, comprises: low-drift voltage reference circuit part, measurement isolation circuit part, platinum resistance temperature sensor and precision instrument amplifying circuit part, The low-drift voltage reference circuit part is composed of a high-precision voltage reference and a fine-tuning sliding rheostat, which provides a low-drift reference voltage for the measurement isolation circuit part; The measurement isolation circuit part is composed of a high-gain high-precision amplifier and a precision resistor with a compensation voltage close to zero, and is used to provide a constant current source for the platinum resistance temperature sensor; The platinum resistance temperature sensor adopts a four-wire connection method, wherein two lead resistances are connected to the measurement isolation circuit part as power leads, and the other two lead resistances are connected to the precision instrument amplifying circuit part as sensing leads; The precision instrument amplifier circuit part is composed of a precision instrument amplifier and a precision resistor, and the two sensing leads of the platinum resistance temperature sensor are connected to the precision instrument amplifier, and the gain of the precision instrument amplifier is controlled by changing the resistance value of the precision resistor . 2. The high-precision temperature measuring device using platinum resistance measurement according to claim 1, characterized in that, the drift of the reference voltage provided by the low-drift voltage reference circuit part is lower than 10×10 ^-6 /°C. 3. The high-precision temperature measuring device utilizing platinum resistance measurement as claimed in claim 1, wherein the input impedance of the precision instrumentation amplifier is high enough to ensure that no current flows through the input terminal.

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