CN101957243A - High-precision temperature measuring device and method - Google Patents

Abstract

The invention provides a high-precision temperature measuring device and a high-precision temperature measuring method. The device comprises a low-drift voltage reference circuit part, an isolation circuit measuring part, a platinum resistor temperature sensor and a precision instrument amplifying circuit part, wherein the low-drift voltage reference circuit part consists of a high-precision voltage reference and a vernier slide rheostat and provides low-drift reference voltage for the isolation circuit measuring part; the isolation circuit measuring part consists of a high-precision amplifier and a precision resistor and is used for providing a constant flow source for the platinum resistor temperature sensor; the platinum resistor temperature sensor adopts a four-wire system connecting method, wherein two wires are connected to the isolation circuit measuring part to serve as power leads and the other two wires are connected to the precision instrument amplifying circuit part to serve as sensing leads; and the precision instrument amplifying circuit part consists of a precision instrument amplifier and a precision resistor and controls the gain of the precision instrument amplifier by changing the resistance of the precision resistor. The high-precision temperature measuring device and the high-precision temperature measuring method have the advantage of implementing high-precision four-wire system temperature measurement of the platinum resistor temperature sensor through the precision instrument amplifier, and are applied in the field of precision temperature measurement with the advantages of low cost, high precision and high stability and consistency.

Description

A high-precision temperature measuring device and measuring method

technical field

The invention relates to a temperature measuring device, in particular to a high-precision temperature measuring device and a measuring method thereof which utilize platinum resistors for four-wire temperature measurement.

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 three general-purpose temperature measuring devices, the object of the present invention is to provide a high-precision temperature measuring device and its measurement method, which realizes high-precision four-wire temperature measurement of platinum resistance temperature sensors through precision instrumentation amplifiers. Measurement, suitable for the field of precision temperature measurement with low cost, high precision, good stability and consistency.

In order to achieve the above object, the present invention provides a high-precision temperature measurement device, 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.

In addition, the present invention also provides a measuring method of a high-precision temperature measuring device, comprising the following steps:

1) 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 constituting the precision instrument amplifier circuit part;

2) According to the gain G of the precision instrumentation amplifier, calculate the voltage at both ends of the platinum resistance temperature sensor: V=Vout/G;

3) Calculate the resistance value Rt=V/I of the platinum resistance temperature sensor by Ohm's law, wherein, I is the constant current source current, and then obtain the accurate temperature by querying the resistance value and the temperature index of the platinum resistance temperature sensor value.

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 and measuring method of the present invention is that it is applicable to 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 composition block diagram of the high-precision temperature measuring device of the present invention.

Fig. 2 is a schematic diagram of the electrical connection of the high-precision temperature measuring device of the present invention.

Fig. 3 is a flow chart of the measuring method of the high-precision temperature measuring device of the present invention.

Detailed ways

A high-precision temperature measuring device and its measuring method 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 of the present invention. As shown in Figure 1, the high-precision temperature measuring device of the present invention 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 connections constituting a high-precision temperature measuring device of the present invention. 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, this high-precision temperature measurement device adopts four-wire platinum resistance temperature measurement. Rx1, RX2, Rx3, and Rx4 are the four lead resistances of the platinum resistance temperature sensor. The sensor is connected to a constant current source, and Rx2 and Rx4 are the sense leads that connect the voltage from the RTD to a 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，本发明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 present invention adopts the precision instrument amplifier circuit to replace the combination of the existing differential amplifier circuit and the single-bipolar conversion amplifier is mainly because the precision of the basic differential amplifier circuit is relatively poor, and the differential amplifier circuit is changed when the amplification gain is changed. , 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 present invention 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 circuit cost.

In addition, Fig. 3 is a flowchart of the measuring method of the high-precision temperature measuring device of the present invention, as shown in Fig. 3, the measuring method of the high-precision temperature measuring device of the present invention comprises the following steps:

1) 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 constituting the precision instrument amplifier circuit part;

2) According to the gain G of the precision instrumentation amplifier, calculate the voltage at both ends of the platinum resistance temperature sensor: V=Vout/G;

3) Calculate the resistance value Rt=V/I of the platinum resistance temperature sensor by Ohm's law, wherein, I is the constant current source current, and then obtain the accurate temperature by querying the resistance value and the temperature index of the platinum resistance temperature sensor value.

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

Claims (4)

1. a high-precision temperature measurement mechanism is characterized in that, comprising: low drift voltage reference circuit part, measurement buffer circuit part, platinum resistance temperature sensor and precision instrument amplification circuits,

Described low drift voltage reference circuit part is made up of high-precision voltage reference and fine setting slide rheostat, and the reference voltage of low drift partly is provided for described measurement buffer circuit;

Described measurement buffer circuit part is made up of near zero high-precision amplifying and precision resistance high-gain and bucking voltage, is used to platinum resistance temperature sensor that constant current source is provided;

Described platinum resistance temperature sensor adopts the four-wire system connection, and wherein, two lead resistances are connected to described measurement buffer circuit part as the power lead-in wire, and the two other lead resistance is connected to the precision instrument amplification circuits as sense leads;

Described precision instrument amplification circuits, form by precision instrument amplifier and precision resistance, two sense leads of platinum resistance temperature sensor are connected to described precision instrument amplifier,, control the precision instrument Amplifier Gain by changing the precision resistance resistance.

2. high-precision temperature measurement mechanism as claimed in claim 1 is characterized in that, the drift of the reference voltage that described low drift voltage reference circuit partly provides is lower than 10 * 10 ^-6/ ℃.

3. high-precision temperature measurement mechanism as claimed in claim 1 is characterized in that, the input impedance of described precision instrument amplifier is enough high, guarantees that input end does not have electric current to flow through.

4. the measuring method of a high-precision temperature measurement mechanism is characterized in that, is the measuring method of any described high-precision temperature measurement mechanism in the described claim 1～3, comprises the steps:

1) will hang down drift voltage reference circuit part, measure buffer circuit part, platinum resistance temperature sensor and after the precision instrument amplification circuits is connected, measure the precision instrument amplifier voltage output voltage V out that constitutes described precision instrument amplification circuits;

2), calculate the voltage at platinum resistance temperature sensor two ends: V=Vout/G according to described precision instrument Amplifier Gain G;

3) calculate the resistance Rt=V/I of platinum resistance temperature sensor by Ohm law, wherein, I is the constant current source electric current, divides kilsyth basalt to obtain the precise dose value by the resistance of inquiry platinum resistance temperature sensor and the relation of temperature then.

Images