A thermocouple is a sensor for measuring temperature. Thermocouples are versatile temperature sensors and are commonly used for a wide range of applications: from industrial thermocouples to standard thermocouples for domestic appliances and equipment.
The thermocouple temperature probe is made up of two metals of different natures connected to one end.
When the junction of these metals is heated or refrigerated, a current is established in the circuit and generates an electromotive force (EMF) which depends on the nature of the wires used.
The quality metals used are homogeneous and allow the thermocouple to be subjected over its entire length to different temperature gradients without disturbing the electromotive force.
The measuring instruments receive the thermocouple directly and control the cold junction.
These thermocouple alloys are generally available in yarns.
There are many models and technical specifications. It is extremely important to understand the basic structure, operating mode and temperature ranges to determine the type and material of the thermocouple best suited for your application.
There are different types of thermocouples:
Polarity must be respected, otherwise additional parasitic EMFs may occur.
Use cables specially adapted to thermocouples, so-called "extension" or "compensation" cables.
Thermocouple is often exposed to a "severe" atmosphere subjected to electrical, electromagnetic and other interferences.
In order to compensate for the temperature disturbances caused by these interferences, the metallic sheathed thermocouples are delivered with an insulation resistance between the wires and the protector.
Rigorously tested at the factory, this insulation resistance is from 1000 MW to 5000 MW minimum at 100 to 500 VDC (depending on the thermocouple diameter and at ambient temperature) for a thermocouple of length less than 1 meter.
These resistance values decrease when the thermocouple is subjected to high temperatures, until it becomes almost zero at very high temperature.
This is why it is always preferable to use measuring instruments with galvanic isolation input / output or input / output / power supply.
Thermocouple temperature sensor
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