Selection of temperature measuring instruments

1. Selection of temperature measuring instruments

Temperature measuring instruments must be selected according to production process requirements and on-site working conditions. First, determine the type of temperature measuring instrument: contact thermometer or non-contact thermometer. Non-contact thermometers are expensive and have low accuracy. Contact thermometers should be used as much as possible as long as working conditions permit. Secondly, select temperature sensing elements reasonably according to the temperature measurement range and accuracy requirements. Usually, thermocouples are selected in the high temperature range and thermal resistors are selected in the low temperature range. Finally, the material and wall thickness of the protective sleeve are reasonably selected according to the properties of the measured medium to avoid damage to the temperature measuring element.

2. Correct installation

The installation position of the instrument must make the temperature measurement point representative, and the installation direction and depth must ensure that the detection element has sufficient contact with the measured medium; the wire outlet holes of the thermocouple and thermal resistor junction boxes should be downward to prevent water accumulation and dust from falling in and causing adverse effects; special care should be taken during installation to avoid mechanical damage or deformation; for working environments with severe corrosion, high temperature and strong vibration, corresponding protective measures should also be considered; signal connection wires should try to avoid AC power wires, etc.

3. Fair Use

When selecting a thermocouple, pay attention to the connection polarity between the compensation wire and the thermocouple. At the same time, be sure to consider the cold end temperature compensation measures. When selecting a thermal resistor, consider the three-wire connection method. The connection between the detection element and the signal transmission wire should be tight to avoid false connection.