Ⅰ, features,
The element that uses the resistance of a conductor or semiconductor to measure temperature with temperature is called a resistance thermometer. It is composed of thermal resistance body (temperature sensing element), connecting wire and display or recording instrument. It is customary for the thermal resistance used as a standard to be called a standard thermometer, while the thermal resistance used for work is directly called a thermal resistance.
1. High accuracy. It has the highest accuracy of all the thermometers commonly used.
2. Large output signal and high sensitivity.
3. Wide temperature measurement range and good stability. In the vibration of small and suitable environment, can
It can maintain stability below 0.1℃ for a long time.
4. No reference points required. The temperature value can be obtained from the measured resistance.
5. The thermal resistance element with fine platinum wire has poor mechanical impact and vibration resistance.
Components of complex structure, large size, therefore, the thermal response time is long, not
Suitable for measuring small volume of transient catamite temperature area.
Ⅱ, principle
The resistance of a body generally varies with temperature. The resistance temperature coefficient is usually used to describe this characteristic. It is defined as: within a temperature interval, when the temperature changes by 1K, the relative change in resistance value, commonly represented by A, is K.
ⅲ. Structure of thermal resistance
The basic structure of industrial thermal resistance is composed of three parts: temperature sensing element (PT100, PT500, PT1000, etc.), inner lead and protection tube. It usually also has parts connected with external measuring and control devices and mechanical devices. Its shape and thermocouple similar, use should pay attention to avoid wrong.
Iv. Thermal resistance internal lead form
1. The lead wire connected to both ends of the thermal resistance temperature sensing element is made of two sides.
2. One end of the thermal resistance temperature sensing element is connected with two leads, and the other end is connected with a lead. This lead form is called three-wire system.
3. Connect two leads on both sides of the thermal resistance temperature sensing element. In precision measurement, the four-wire system should be used. This kind of lead can not only eliminate the influence of the resistance of the inner lead, but also eliminate the influence of the resistance when the resistance value of the connecting wire is the same.