Thermocouple signal noise

[Raees]

Hello. This is Raees. I am designing a K-type Thermocouple amplifier, using INA114 (Instrumentation amplifier). Cold Junction is compensated. the problem is, Output signal of thermocouple is noisy. I have to tried to pass this signal through Low pass RC filter. Still there is noise alot.
One thing more. Input and output signal is also having 50 to 60Hz of frequency

can someone suggest, how to remove the noise.

First Image: Ouput signal of Thermocouple at room temprature 25'C (1mV), Fed into Instrumentation Amplifier.



Second Image:Zoom View (Ouput signal of Thermocouple at room temprature 25'C (1mV)



Third Image: Output of Instrumentation Amplifier.


Fourth Image: Oscilloscope Probe-Open(Not Connected)

 

[chuckey]

So your thermocouple has no hum output, but the amplifier has. So is the power supply lines clean of AC ripple, I would think they will be as they tend to use diode bridges, so hum would be 100 HZ.
So the amp must be picking up hum by itself, is it screened? You could try switching things off adjacent to where you are working, but this cuts the AC current but not the voltage. If you view the scope and switch off the device causing the problem, the hum will IMMEDIATELY clear (including the amps own PSU). Thermocouples are sloow devices so a LF filter with a 10 HZ cut off would not effect its operation?
Frank