Types of contact thermometers
1. Expansion thermometer
Using the principle of thermal expansion and contraction of solids or liquids to measure temperature, a common thermometer is the liquid expansion thermometer. There are rod thermometers that use solid expansion to change length due to thermal expansion and contraction, and bimetallic thermometers that use bimetallic sheets to bend and deform when heated.
2. Pressure thermometer
It converts temperature measurement into pressure measurement based on the principle that liquid or gas sealed in a fixed container changes pressure when temperature changes. It mainly consists of two parts: one is the temperature bulb, which is composed of a temperature sensing fixed container for holding liquids or gases, and the other is an elastic element that reflects pressure changes.
3. Thermocouple thermometer
According to the thermoelectric effect, when two different conductors are in contact and form a circuit, if the temperatures of the two contacts are different, a millivolt level thermoelectric potential will appear in the circuit, which can accurately reflect the temperature.
4. Resistance thermometer
Measure temperature using the characteristic of the resistance of metals or semiconductors changing with temperature.
Advantages of contact thermometers
(1) The temperature measurement accuracy is relatively high, intuitive and reliable;
(2) The system structure is relatively simple, and the price of temperature measuring instruments is relatively low;
(3) Can measure the temperature of any part;
(4) Convenient for multi-point centralized measurement and automatic control.
