Analog Inputs Outputs PLC Basics PLC Learning Sensors

The Secret Of Getting Rid Of Noise On Your Analog Signal

Allot of times in industrial environments we get noise on the analog signal input to PLC’s or other controllers. The noise can be generated by motors, bad wiring, etc.

Placing a 1- 100 uF capacitor on the input signal and ground (common to the cabinet)  will reduce the noise that the input is receiving.

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5 replies on “The Secret Of Getting Rid Of Noise On Your Analog Signal”

Hi… Garry
Whether we have to use capacitor in parallel with analog sensor?

Is it possible to use twisted wire for analog input instead of capacitor?


Hi Abdul,
Twisted wire is a good idea for external noise along the path. Depending on the type of noise it will cancel it out due to the twisting of the wire. The capacitor will also try to filter this noise out in a more progressive manner. Try the circuit without and with the capacitor to see a difference.

How about for thermocouple inputs? Put the cap between the legs of the input or just the positive to ground? I think the second, but since both legs make the input, maybe one cap on each leg?

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