Induced Voltage Activating Input

I have a 24v DC input that is coming on from about 9 volts of induced voltage. I believe I can connect a resistor between the input and 0v to "pull down" this voltage to an acceptable level. Not sure of what value and wattage to use. Any help appreciated! Thanks!

Whats causing the induced voltage..How about correcting that?

Hi Bob...I knew somebody would say that. The machine was installed with AC and DC in the same cable. This should be fixed, for sure. For now, the machine needs to run.

You just need to make sure the resistor won't overheat with 24 Volts on full time or load down the device it originates from
e.g. 1/4 Watt
0.25/24 = 0.01 mA
24/0.01 = 2400 Ohms (minimum)
Assuming your cable is < 100 meters I think you will find a much larger resistor will do the trick e.g. 10K
Please let us know the final solution.
I assume your cable is not one with shielded pairs.
Roy

If your cable has any spare unused cores in it make sure you tie them to earth rather than leave them floating, this can help to reduce induction effects.

How about using your present suspect plc "input" to energise a standard 24v dc relay which would then switch 24v to your plc input. The relay would be less likely to operate with a small induced voltage.