Using 4-20mA valves

Since the RMCs have ±10V outputs, Delta does not recommend using valves or drives that require a 4-20mA input. Delta recommends using a valve or drive that requires a ±10V input voltage or, for servo valves, a current centered around 0, such as ±90mA. However, for the cases where 4-20mA cannot be avoided, this is how to to set up the RMC parameters to work together with the VC2124 voltage-to-current converter to produce a 4-20mA output:

  1. Set the VC2124 current range to ±20mA.
  2. Set the Output Scale to 4V/100%.
  3. Set the Output Bias to 6V.
  4. Set the Output Limit to 4V (this keeps the output from going below 4mA).

Inverting the Output
If a positive voltage makes the system move in the wrong direction, you will need to invert the output. To do so, do steps 1-4 above, but set the Invert Output Polarity bit and set the Output Bias to -6V.

Any special considerations if using a +/- 20ma valve with the VC2124 ?

+/- 20 ma is easy. You just turn the current range switch on the VC2124 until is provides +/- 20 ma when provided +/- 10 volts. +/- 10 volts is default from the controller so there is nothing to configure there…