Here P2 + and P4 S+ are shorted and P4 S- is left open. PT100 is connected between P2 + and -.
The device works fine and gives proper output in my lab but it is to be used in an electrical control panel that has VFDs (Variable Frequency Drives). When the load is connected to the drives, the output of my amplifier turns 0. The weird part is if I connect a multimeter to measure the output, it gets to a value near the desired output but fluctuates. I put a 1M resistor across the output but it makes no difference.
The input power supply remains same as well as the input to the amplifier across P4 S- and P4 S+ remains very stable.
This might be the noise from the VFD harmonics causing this. I tried using shielded wire but no difference.
Is there a way to prevent the effect of noise on my amplifier. Some sort of a filter. Please suggest. Thanks for all the help in advance.
Also, I don't have access to the VFD. All I can do is modify the transmitter (Amplifier) and replace the existing one.