I use a grounded USB TC-08. I am using K-type thermocouples to monitor the temperatures of the surface of a bulb which outputs UV light. The bulbs are very similar to normal strip fluorescent bulbs, but the surface can get to 950 degrees C.
However during testing I can be seeing normal temperatures from 800 - 950 C when the readings will suddenly drop off to around half, where nothing in the system I am testing has changed. Strangely I can turn the bulb off and the normal temperature reading can be obtained again, before the bulb starts to cool down. This suggests that the bulb is causing some interference in the thermocouples which translates to poor results. Could this be the case? Or is there another possibility?