Three-wire-system thermal resistor measuring circuit

Abstract

The invention discloses a three-wire-system thermal resistor measuring circuit. The three-wire-system thermal resistor measuring circuit comprises: a constant current source is connected with a first terminal which is connected with a three-wire-system thermal resistor, for providing excitation for the three-wire-system thermal resistor; the first input end of a signal conditioning module is connected with the constant current source, the second input end of the signal conditioning module is connected with a second terminal which is connected with the three-wire-system thermal resistor, and the third input end of the signal conditioning module is connected with DC bias voltage; and the output end of the signal conditioning module is connected with the input end of an amplification circuit, the output end of the amplification circuit is connected with an A / D sampler, and the voltage of the A / D sampler forms a linear relation with the resistance of the thermal resistor.

Description

technical field [0001] The invention relates to the technical field of high-precision temperature measurement, in particular to a three-wire thermal resistance measurement circuit. Background technique [0002] High-precision temperature measurement is an important topic in the field of industrial production. The thermal resistance made of metal platinum material has become an ideal temperature measuring element widely used in industrial temperature measuring systems due to its high precision, stability, reproducibility and good interchangeability. Since the three-wire thermal resistance has the characteristics of low cost, convenient wiring, and high measurement accuracy, it is currently the most commonly used thermal resistance wiring method. The widely used three-wire thermal resistance measurement methods include the unbalanced bridge method and the double constant current source method. [0003] Such as figure 1 Shown is the measurement principle diagram of the three...

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Problems solved by technology

Although this method can eliminate the influence of the wire resistance r on the measurement results, its measurement accuracy is based on the good consistency of the currents of the two constant current sources.

In practical applications, any constant current source will have time drift and temperature drift, and the consistency of the constant current source will be affected, resulting in large measurement errors

[0005] Chinese patent 200810036435.6 discloses a thermal resistance three-wire system, four-wire system multiplexing temperature measurement method, the invention disclosed three-wire thermal resistance measurement method is not accurate, and does not take into account the matching accuracy of the double constant current source

[0006] Chinese patent 201110161316.5 discloses a method for reducing the measurement error of the three-wire thermal resistance. Although the measurement method of the three-wire thermal resistance disclosed in the invention can greatly reduce the influence of the matching error of the double constant current source on the sampling value of the thermal resistance, it needs to increase The additional control circuit realizes the switching of the connection relationship between the two constant current sources and the thermal resistance, which increases the complexity of the measurement system and is not conducive to the remote measurement of temperature

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