Principle of Thermistor Temperature Measurement and Related Materials

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Date: 2021-06-16Read: 8

Principle and Materials of Thermistor Temperature Measurement

Thermistor is in the medium low temperature rangecommonly usedA temperature detector. Its main features are high measurement accuracy and stable performance. Among them, platinum resistance thermometer has the highest measurement accuracy. It is not only widely used in industrial temperature measurement, but also made into a standard reference instrument.

1、 Principle and Materials of Thermistor Temperature Measurement

Thermal resistance temperature measurement is based on the characteristic that the resistance value of metal conductors increases with temperature.

Thermistors are mostly made of pure metal materials, with platinum and copper being the most commonly used. In addition, materials such as Dian, nickel, manganese, and rhodium have been used to manufacture thermistors.

1Temperature characteristics of platinum thermistor

（1）In0~850℃Within the scope:

Rt=R0(1+At+Bt2)

（2）In-200~0℃Within the scope:

Rt=R0[1+At+Bt2+C(t-100) t3]

in the formulaATheBTheCThe coefficients are:A=3.90802×10^-3C^-1 ；B=-5.802×10^-7C^-2C=-4.27350×10^-12C^-4

The relationship between the resistance value of platinum resistors and temperature is determined by the stop two equation.

2Temperature characteristics of copper thermistor

In-50~150℃Within the scope:

Rt=R0(1+At+Bt2+Ct3)

in the formulaA=4.28899×10^-3C^-1；B=-2.133×10^-7C^-2；C=1.233×10^-9C^-3

The division relationship between copper resistance and temperature is determined by the above equation, and the technical performance of platinum resistance and copper resistance is shown in the table1-1

table1-1Technical performance of commonly used thermal resistors

name		graduation mark	Temperature range ℃	The temperature is0Resistance at ℃R₀，Ω	Resistance ratio R₁₀₀/R₀	Main Features
Standard thermistor	rtd(WZP)	Pt10	-200~850	10±0.01	1.385±0.001	high measurement accuracy,Good stability,Can be used as a reference instrument
		Pt50		50±0.05	1.385±0.001
		Pt100		100±0.1	1.385±0.001
	Copper resistance(WZC)	Cu50	-50~150	50±0.05	1.428±0.002	Good stability,cheap;But the volume is large,Low mechanical strength
	Copper resistance(WZC)	Cu100	-50~150	100±0.1	1.428±0.002
	Nickel resistanceWZN	Ni100	-60~180	100±0.1	1.617±0.003	high sensitivity,compact size;But the stability and reproducibility are poor
		Ni300		300±0.3	1.617±0.003
		Ni500		500±0.5	1.617±0.003
Low temperature thermistor	Indium resistance		3.4~90K	100		Good reproducibility,In4.5~15KWithin the temperature range,Sensitivity ten times higher than platinum resistance;But the reproducibility is poor,Soft material,deformable
	Rhodium iron thermistor		2~300K	20、50or100 R_4.2k/R_273kapproximately0.07		Has high sensitivity,Good reproducibility,In0.5~20KAccurate measurement can be made within the temperature range;But the long-term stability and reproducibility are poor
	Platinum cobalt thermistor		2~100K	100 R_4.2k/R_273kapproximately0.07		Good thermal response, natural small, good mechanical properties, temperature below300KAt this time, the sensitivity is much higher than that of platinum; But it cannot be used as a standard thermometer

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