Working Principle of electronic thermometer
electronic thermometer is divided into thermocouple thermometer and resistance temperature thermometer according to its different principles. Resistance temperature thermometer is more common.
Working principle of resistance temperature thermometer
resistance temperature thermometer is the most commonly used temperature detector in medium and low temperature areas. Its main features are high measurement accuracy and stable performance. Among them, platinum resistance temperature has the highest measurement accuracy. It is not only widely used in industrial thermometry, but also made into a standard benchmark.
1. Resistance temperature temperature measurement principle and materials
resistance temperature temperature measurement is based on the characteristic that the resistance value of metal conductor increases with the increase of temperature. Most of the resistance temperature are made of pure metal materials, and platinum and copper are the most widely used at present. In addition, nickel, manganese, RH and other materials have been used to manufacture resistance temperature.
2. Type of resistance temperature
1) ordinary resistance temperature
according to the temperature measurement principle of resistance temperature, the change of measured temperature is directly measured by the change of resistance temperature resistance value. Therefore, the change of resistance of various wires such as the lead-out line of the resistance temperature body will affect the temperature measurement.
2) armored resistance temperature
armored resistance temperature is a solid body composed of temperature sensing element (resistor), lead wire, insulation material and stainless steel casing. Its outer diameter is generally & phi;2 -- & phi;8mm, the minimum is & phi;1mm. Compared with ordinary resistance temperature, it has the following advantages: ① small volume, no gap inside, small measurement lag in thermal inertia; ② mechanical properties, vibration resistance, impact resistance; ③ can bend, easy to install ④ long service life.
3) end face resistance temperature
end face resistance temperature temperature sensing element is wound by specially processed resistance wire, which is close to the end face of thermometer. Compared with general axial resistance temperature, it can reflect the actual temperature of the measured end face more correctly and quickly, and is suitable for measuring the end face temperature of bearing Bush and other parts.
4) flameproof resistance temperature
the explosion-proof resistance temperature limits the explosion of explosive mixed gas inside its shell due to the influence of spark or arc in the junction box through the junction box with special structure, and the production site will not lead to super explosion. Explosion-proof resistance temperature can be used to measure the temperature of places with explosion danger in bla-b3c level area.
Resistance temperature the resistance value of the sensor of thermometer varies with temperature, and there are many implementation methods.
1. Connect the constant current to the sensor, and measure the voltage value at both ends to correspond to the temperature one by one.
2. Connect the series resistor to the constant voltage and measure the sensor partial pressure value. Convert to temperature.

Digital thermometer is one of the types of temperature measuring instruments. There are kerosene thermometer, alcohol thermometer, mercury thermometer, gas thermometer, resistance thermometer, thermocouple thermometer, radiation thermometer and light thermometer, bimetallic thermometer, etc.