Here you can see the result, if we put out the power supply from the laptop. After some time we put it in, and put it out...,in,out,in,out and so on.

Thank you for your answer. We use the furnace "Nabertherm LT/5/11/HA/P330. I made sure, that the thermocouples are not in electrical contact with the furnace or any kind of foreign body. We also tried something: The furnace ist connnect to the electric circuit 1 and we connected the laptop to the el...

Hallo! We could find the problem. We used a Laptop for this application. Our USB port is direct right next to the power supply. During a measurement with these frequencies we remove the power supply from the laptop and the frequencies were gone. Do you now why this is a problem for the datalogger ? ...

Hallo ! We measure temperature of our furnace. We use the USB PICO TC-08 with Typ J Elements and also Typ J miniature plug. (Typ J elements measures temperature up to 750 °C) On the red curve you can see the thermocouple inside the furnace and on the blue curve you can see an elements placed outside...