The correct selection method for thermocouples

Thermocouples are commonly used temperature measuring components in temperature measuring instruments. They directly measure temperature and convert the temperature signal into a thermoelectric potential signal, which is then converted into the temperature of the measured medium through electrical instruments (secondary instruments). Today we will specifically introduce the correct selection method for thermocouples, hoping to help users better apply their products.

1. The selection of measurement accuracy and temperature measurement range is generally based on the use of B-type thermocouples when the temperature is between 1300~1800 ℃ and the required accuracy is relatively high; The requirement for accuracy is not high, and the atmosphere allows for the use of tungsten rhenium thermocouples. Generally, tungsten rhenium thermocouples are selected for temperatures above 1800 ℃; S-type thermocouples and N-type thermocouples are available for use at temperatures ranging from 1000 to 1300 ℃, which require high accuracy; K-type and N-type thermocouples are generally used below 1000 ℃, while E-type thermocouples are generally used below 400 ℃; At 250 ℃ and negative temperature measurements, T-type thermocouples are generally used. At low temperatures, T-type thermocouples are stable and have high accuracy.
2. The selection of atmosphere for S-type, B-type, and K-type thermocouples is suitable for use in strong oxidizing and weak reducing atmospheres, while J-type and T-type thermocouples are suitable for weak oxidizing and reducing atmospheres. If a protective tube with good airtightness is used, the requirements for the atmosphere are not too strict. Humidity sensor probe, stainless steel electric heating tube PT100 sensor, cast aluminum heater, heating coil fluid solenoid valve
3. The selection of durability and thermal responsiveness: Thermocouples with larger wire diameters have better durability, but slower response. For thermocouples with larger heat capacity, the response is slower. When measuring temperatures with large gradients, temperature control is poor under temperature control. It is required to have a fast response time and a certain degree of durability, so choosing an armored puppet is more suitable.
4. The nature and state of the measured object affect the selection of thermocouples. High mechanical strength is required for temperature measurement of moving objects, vibrating objects, and high-voltage vessels. Protective tubes are required for atmospheres with chemical pollution, and high insulation is required in the presence of electrical interference.