PLC to Speedpot

10 V DC from your what?
Anyhow, if the polarity is right, just substitute your 0-10 V for the pot input. Do not forget to connect your "what?" device's zero (analogue ground) to the drive's analogue ground.
If the polarity isn't right, you may need a loop isolator with 10 V in and 10 V out (a standard device) to get it right.

Gunnar Englund
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Half full - Half empty? I don't mind. It's what in it that counts.

Does the drive have a 0-10VDC analog input to match to the analog out of the PLC? If not you will need a signal conditioner with an input to match the PLC analog output and with an output to match the drives potentiometer setup what ever that is.

first time you check program speedpot plc is there have speedpot program or not?
if it's the plc inside has program for speedpot, try set speed to 50% then check output analog plc its must be around 5 Vdc.
if ok then connect 0 V from analog output PLC to 0V terminal your DC drive and connect 10V from analog output PLC to terminal Vin for speed control at your DC drive.