Rheostat with Hydraulic Amplifier Card
Your circuit has several problems:


A 5 &Omega; resistance on a 24 V supply could supply almost 5 A and that's at maximum resistance. The card will only require mA. The 5 &Omega; resistor will not limit the voltage so the 24 V will be passed through and may destroy the card.
There is no limit on your adjustment.








simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. A possible solution.

How it works:


R1 and R2 form a 24:10 divider reducing the 24 V to 10 V at the top of R2. This means that R2, when wired as a potentiometer, can be adjusted so that its wiper voltage varies from 0 to +10 V and can't be adjusted above +10 V by the operator.
R3 and R4 perform the same function for the negative voltages.
With both FWD and REV relays off (as shown) the control input is grounded ensuring that it is held at zero volts and can't take off due to interference or stray voltages on a floating input.
When FWD is energised the voltage set by R2 is fed into the input.
When REV is energised the voltage set by R4 is fed into the input.
FWD will override REV if both are switched on simultaneously due to PLC error. You can reverse this logic, if required.