How to check the thermocouple

The resistance of a thermocouple can be measured to understand if a thermocouple of the OPTIC inlet or cryotrap is broken or not. A digital multimeter is needed to check the resistance between the 2 thermocouple pins.

Switch off the instrument and unplug the inlet or coldtrap thermocouple from the controller. Measure the resistance between the 2 silver colour pins. (the copper colour pin is ground pin).

The resistance should be around 15 Ohm for the inlet and 200 ohm for the coldtrap. 

See the pictures below: