Thermocouple burning detection

The most common fault mode of the thermocouple is the failure of the fault, also known as "burning".

For any voltage measurement instrument with high input impedance, there is a problem with the hot -electric puppet on the road, because the lack of complete circuits on the input terminal can detect the surrounding source (power cord, electric motor, variable frequency motor drive)) Electric noise is mistakenly interpreted by the instrument as a temperature that changes violently.

For this reason, it is wise to design some measures to generate some consistent state in the thermocouple instrument without a complete circuit. This is called the burning mode of the thermal puppet instrument.

The following figure shows a simple thermocouple circuit with a burning detection function < /u>:

In the case of thermocouple opening, the resistor in this circuit provides a path for the current. Its size is within the Zhaou, so that it can minimize it during the normal operation period after the thermocouple circuit is completed. Only when the thermocouple is broken, the small current of the resistor can have any substantial impact on the indicator of the voltage meter.

SPDT switch provides optional burning mode: In the case of thermocouple burning , we can configure the instrument to read high temperature (generated by the inner millinter of the instrument) or low temperature (grounded ground (grounding) ), Specifically depending on what we think the safest fault mode for the application.