High-precision platinum resistor temperature measuring device and method

Abstract

The invention provides a high-precision platinum resistor temperature measuring device and method.The temperature measuring device comprises a resistor temperature measuring device body, and the resistor temperature measuring device body comprises a main control chip, an AD chip, a constant current source circuit and a platinum resistor PT; the AD chip is used for carrying out voltage acquisition through an input end when the current output by the constant current source passes through the platinum resistor PT connected with the four-wire system, and the AD chip is also used for carrying out calibration processing on the current in the acquisition circuit; the main control chip is used for inversely solving the resistance value of the platinum resistor PT and converting the resistance value into a temperature value, the temperature measurement circuit is simple in structure, and high-precision measurement can be achieved by eliminating the influence of the lead resistance and calibrating the current output of the constant current source. A four-wire system resistance measuring method is adopted, and errors caused by wire resistance can be completely eliminated. In addition, a nominal resistor with low temperature drift and high precision is arranged in the acquisition circuit, the current of the constant current source is calibrated, errors caused by hardware are reduced, and the measurement precision is improved.

Description

Technical Field

[0001] This invention relates to the field of temperature measurement technology, specifically to a high-precision platinum resistance temperature measuring device and method. Background Technology

[0002] Temperature, as a fundamental environmental parameter, plays a vital role in people's production, daily life, and scientific research activities. Temperature detection is widely used in industrial automation and scientific research, and improving the accuracy of temperature measurement is of great significance to temperature measurement systems. Platinum resistance thermometers (PTTs) measure temperature by utilizing the property that the resistance of metallic platinum changes with temperature. Due to their stable characteristics, PTTs offer advantages such as a wide temperature range, good linearity, and fast response, making them a widely used element for temperature measurement.

[0003] Traditional platinum resistance thermometry methods (two-wire or three-wire methods) neglect the equivalent resistivity of the wires when testing temperature. This equivalent resistance introduces interference. When the resistance being tested is extremely small, the resulting error in the temperature measurement system is significant, and large errors are unacceptable in precision measurements. Furthermore, errors caused by the constant current source circuit hardware in high-precision measurements cannot be ignored. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a high-precision platinum resistance temperature measurement device and method to solve the problems mentioned in the background section. The present invention employs a four-wire resistance measurement method, which can completely eliminate errors caused by wire resistance. Furthermore, a low-temperature drift, high-precision nominal resistor is incorporated into the acquisition circuit to calibrate the constant current source, reducing hardware-related errors and improving measurement accuracy.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a high-precision platinum resistance temperature measuring device, comprising a resistance temperature measuring device body, wherein the resistance temperature measuring device body includes a main control chip, an AD chip, a constant current source circuit, and a platinum resistance thermometer (PT). The AD chip is used to acquire voltage data through its input terminal when the current output from the constant current source passes through the four-wire connected platinum resistance thermometer (PT). The AD chip is also used to calibrate the current in the acquisition circuit. The main control chip is used to inversely solve for the resistance value of the platinum resistance thermometer (PT) and convert it into a temperature value.

[0006] Furthermore, the main control chip is an STM32F103C8T6 main control chip, and the platinum resistance PT is a four-wire platinum resistance PT.

[0007] Furthermore, the resistance temperature measuring device also includes a voltage reference source, which is connected in parallel across the constant current source chip and serves as a 1.25V Zener diode.

[0008] Furthermore, it also includes a nominal resistor, which is used to eliminate the influence of the hardware on the constant current of the constant current source.

[0009] A temperature measurement method using the above-mentioned temperature measuring device includes the following steps: constant current source setting, four-wire connection and voltage acquisition, constant current source current calibration, platinum resistance value calculation, and temperature inverse solution.

[0010] Furthermore, during the constant current source setup process, a voltage reference chip is used in conjunction with the constant current source chip to generate a constant current by setting the resistance value of the precision resistor R1.

[0011] Furthermore, in the four-wire connection and voltage acquisition process, the platinum resistance is connected to the constant current source and the AD acquisition chip via a four-wire connection. Current is applied to the input terminal of the constant current source, and the AD chip acquires the voltage across the platinum resistance; thus eliminating the influence of wire resistance on voltage measurement.

[0012] Furthermore, during the constant current source calibration process, a high-precision nominal resistor is connected to the acquisition circuit. The AD chip acquires the voltage across the nominal resistor and calculates the actual constant current source current after calibration, thus eliminating the influence of hardware errors on the constant current source current.

[0013] Furthermore, in the process of calculating the resistance value of the platinum resistance, the actual resistance value of the platinum resistance is calculated by using the collected voltage across the platinum resistance and the calibrated current.

[0014] Furthermore, during the temperature inversion process, the real-time temperature is obtained based on the relationship between the platinum resistance value and the temperature.

[0015] The beneficial effects of this invention are:

[0016] 1. The temperature measuring circuit of this high-precision platinum resistance temperature measuring device has a simple structure. By eliminating the influence of lead resistance and calibrating the constant current source output, high-precision measurement can be achieved.

[0017] 2. This invention employs a four-wire resistance measurement method, which can completely eliminate errors caused by wire resistance. Furthermore, a low-temperature drift, high-precision nominal resistor is incorporated into the acquisition circuit to calibrate the constant current source, reducing hardware-related errors and improving measurement accuracy. Attached Figure Description

[0018] Figure 1 This is a circuit block diagram of a high-precision platinum resistance temperature measuring device according to the present invention;

[0019] Figure 2 A four-wire platinum resistance temperature measurement circuit diagram provided in an embodiment of the present invention;

[0020] In the diagram: N1 is the LT3092 current source chip, N2 is the LT1634AIS8-1.25 voltage reference chip, the AD chip is a 24-bit AD7714 module, R1 is the constant current source current parameter setting resistor, R2, R3, R5, and R6 are lead resistors, R4 is a PT platinum resistance thermometer, R7 is the nominal resistor used for current calibration in the voltage acquisition circuit, C1, C2, and C3 are filter capacitors, Vp1+ / - is the voltage across the platinum resistance thermometer PT, and Vr1+ / - is the voltage across the nominal resistor. Detailed Implementation

[0021] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0022] Please see Figures 1 to 2 This invention provides a high-precision platinum resistance temperature measuring device, comprising a main body, a main control chip, an AD chip, a constant current source circuit, and a platinum resistance thermometer (PT). The AD chip is used to acquire voltage data through its input terminal when the current output from the constant current source passes through the four-wire connected platinum resistance thermometer (PT). The AD chip is also used to calibrate the current in the acquisition circuit. The main control chip is used to inversely solve for the resistance value of the platinum resistance thermometer (PT) and convert it into a temperature value.

[0023] This embodiment also provides a temperature measurement method using the above-mentioned temperature measuring device, including the following steps:

[0024] Constant current source setting: Using a voltage reference chip in conjunction with a constant current source chip, a constant current is generated by setting the resistance value of precision resistor R1;

[0025] Four-wire connection and voltage acquisition: Connect the platinum resistance thermometer to the constant current source and the AD acquisition chip using a four-wire connection. Apply current to the input terminal of the constant current source, and the AD chip acquires the voltage across the platinum resistance thermometer; this eliminates the influence of wire resistance on voltage measurement.

[0026] Constant current source calibration: A high-precision nominal resistor is connected in the acquisition circuit. The AD chip acquires the voltage across the nominal resistor and calculates the actual constant current source current after calibration, thus eliminating the influence of hardware errors on the constant current source current.

[0027] Platinum resistance resistance value calculation: Calculate the actual resistance value of the platinum resistance resistance using the collected voltage across the platinum resistance and the calibrated current;

[0028] Temperature inverse solution: The real-time temperature is obtained from the relationship between the resistance of the platinum resistance thermometer and the temperature.

[0029] Based on the above temperature measurement method, this embodiment also provides the following specific solution:

[0030] The high-precision platinum resistance temperature measuring device in this embodiment includes: an STM32F103C8T6 main control chip, an AD chip, a constant current source circuit, and a platinum resistance PT.

[0031] In this example, the voltage reference source is LT1634AIS8-1.25, which is connected in parallel across the constant current source chip LT3092. It is equivalent to a 1.25V Zener diode. By setting the precision resistor R1, a constant current I can be obtained, i.e., I = 1.25V / R1.

[0032] When a constant current source is applied to point A using a four-wire temperature measurement device, a voltage drop will occur across points A and D. This voltage drop includes the voltage drop across the equivalent resistance of the wires. Therefore, instead of measuring the voltage across A and D, the voltage drop across points B and C is measured. Generally, the input acquisition terminal of an AD chip has high impedance, and almost no current flows through the AD chip. The voltage across the equivalent resistances R3 and R5 of the wires is 0. The four-wire temperature measurement method eliminates the voltage drop across the equivalent resistances R3 and R5, thus accurately measuring the true voltage drop Vp1+ / - generated when the constant current source passes through the platinum resistance thermometer PT.

[0033] Due to hardware errors, the constant current generated by the constant current source may deviate from the constant current IS set by the precision resistor R1. At this time, a nominal resistor with a resistance accuracy of 0.1% and a temperature drift coefficient of 1ppm is introduced. The voltage sampled by the AD chip across R1 is Vr1+ / -.

[0034] (Vr1+ / -) / R1=IS is the calibrated constant current source current in the acquisition circuit, thus eliminating the influence of hardware on the constant current source constant current.

[0035] The relationship between the resistance value RPT of a platinum resistance thermometer and temperature T is RPT = R0[1 + AT + BT2] (0℃~850℃), where R0 is the resistance value at 0℃, and A and B are experimental constants. When T>0, A=3.9083*10-3℃-1, B=-5.775*10-7℃-1.

[0036] The resistance value of the platinum resistance thermometer PT is obtained through the acquisition circuit:

[0037] RPT= (Vp1+ / -) / IS=(Vp1+ / -) / [(Vr1+ / -) / R1]

[0038] Since the resistance of a platinum resistance thermometer has a strong linear relationship with temperature, the real-time temperature can be calculated by solving the quadratic equation RPT=R0[1+AT+BT2], i.e., T=[-A+√A2-4B(1-RPT / R0)] / 2B.

[0039] The foregoing has shown and described the basic principles and main features of the present invention and its advantages. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.

[0040] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high-precision platinum resistance temperature measuring device, comprising a resistance temperature measuring device body, characterized in that: The resistance temperature measuring device includes a main control chip, an AD chip, a constant current source circuit, and a platinum resistance thermometer (PT). The AD chip is used to acquire voltage through the input terminal when the current output from the constant current source passes through the four-wire connected platinum resistance thermometer (PT). The AD chip is also used to calibrate the current in the acquisition circuit. The main control chip is used to inversely solve the resistance value of the platinum resistance thermometer (PT) and convert it into a temperature value.

2. The high-precision platinum resistance temperature measuring device according to claim 1, characterized in that: The main control chip is an STM32F103C8T6 main control chip, and the platinum resistance PT is a four-wire platinum resistance PT.

3. The high-precision platinum resistance temperature measuring device according to claim 1, characterized in that: The resistance temperature measuring device also includes a voltage reference source, which is connected in parallel across the constant current source chip and serves as a 1.25V Zener diode.

4. The high-precision platinum resistance temperature measuring device according to claim 2, characterized in that: It also includes a nominal resistor, which is used to eliminate the influence of the hardware on the constant current of the constant current source.

5. A temperature measurement method using the temperature measuring device as described in claim 1, characterized in that, The process includes the following steps: constant current source setup, four-wire connection and voltage acquisition, constant current source current calibration, platinum resistance value calculation, and temperature inversion.

6. The temperature measurement method according to claim 6, characterized in that: During the constant current source setup process, a voltage reference chip is used in conjunction with the constant current source chip to generate a constant current by setting the resistance value of the precision resistor R1.

7. The temperature measurement method according to claim 6, characterized in that: In the four-wire connection and voltage acquisition process, the platinum resistance thermometer is connected to the constant current source and the AD acquisition chip via a four-wire connection. Current is applied to the input terminal of the constant current source, and the AD chip acquires the voltage across the platinum resistance thermometer, thus eliminating the influence of wire resistance on voltage measurement.

8. The temperature measurement method according to claim 6, characterized in that: During the constant current source calibration process, a high-precision nominal resistor is connected to the acquisition circuit. The AD chip acquires the voltage across the nominal resistor and calculates the actual constant current source current after calibration, thus eliminating the influence of hardware errors on the constant current source current.

9. The temperature measurement method according to claim 8, characterized in that: In the process of calculating the resistance value of the platinum resistance, the actual resistance value of the platinum resistance is calculated by using the collected voltage across the platinum resistance and the calibrated current.

10. The temperature measurement method according to claim 6, characterized in that: During the temperature inversion process, the real-time temperature is obtained based on the relationship between the resistance of the platinum resistance and the temperature.

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