How can thermocouples and thermal resistors measure temperature accurately?

Thermocouples and thermal resistors are the most common temperature measuring elements. They are both contact temperature measurement, so the probe must be able to quickly and truthfully reflect the temperature of the object being measured. The object being measured may be solid, liquid, colloid, gas, etc.

Solid temperature measurement: If the surface temperature of a solid is measured, the probe must be fastened to the solid surface with screws or glue. In order to fully contact the solid surface, the probe is generally made into a flat shape; if the internal temperature of a solid is measured, a hole must be opened in the solid, the probe must be inserted into the hole, and then filled with a filler with strong thermal conductivity.

Liquid, colloid, gas temperature measurement: Since the object being measured is flowing, the temperature probe only needs to be fastened and suspended inside the material, so that the material components can fully wrap the probe. In addition, since heat convection will occur inside the object being measured, the probe only measures the local temperature. If the temperature of the entire object being measured is to be measured, the object being measured needs to be stirred to make the internal temperature as uniform as possible.

However, the temperature measured by the probe is actually the temperature of the object being measured transmitted to the probe sensing head, which takes time. If the probe is not in good contact with the object being measured, or the probe induction head is poorly assembled, or the probe stays on the object being measured for too short a time, it will lead to inaccurate measurement.

In order to protect the probe induction head, we usually put a metal sleeve on the outside of the induction head. The metal sleeve is to protect the induction head from damage (impact, wear, corrosion, etc.). In order to make the induction head respond faster, the metal sleeve must be made of a material with strong thermal conductivity. The wall thickness should be as thin as possible while ensuring mechanical strength, which can reduce the thermal inertia of the probe.

Finally, the wires, connectors, transmitters, collectors, etc. used for thermocouple and thermal resistor signal transmission must use dedicated corresponding models and cannot be mixed, misused, or misused.