I have the attached circuit used as an amplifier for a K type thermocouple, I get a 50Hz noise - the noise appears on both thermocouple inputs and gets amplified - thermocouple wires are shielded with the shield connected to chassis (which is earthed).
Trying to understand the problem I saw that the noise actually comes from the GNDREF node (which is the 0V of the power supply). Connected a 0.1uF capacitor between GNDREF and the chassis and this solved the problem.
I wonder if there is another way to suppress this noise.
Note: later on the circuit will get power from an isolated DC-DC converter, but at the moment it is connected to a lab power supply, so maybe when the isolated supply will be ready the problem will not appear, however I would like to know if there can be another solution at the current stage.
Trying to understand the problem I saw that the noise actually comes from the GNDREF node (which is the 0V of the power supply). Connected a 0.1uF capacitor between GNDREF and the chassis and this solved the problem.
I wonder if there is another way to suppress this noise.
Note: later on the circuit will get power from an isolated DC-DC converter, but at the moment it is connected to a lab power supply, so maybe when the isolated supply will be ready the problem will not appear, however I would like to know if there can be another solution at the current stage.
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