Re: [CAD_CAM_EDM_DRO] 4-20 mA signal

peteryco wrote:

> Hello friends,
> it is a little while ago I didn't post because of a family
> arrangement. But today I need a little help on a off topic not so off
> topic theme.
> I got a pneumatical a steam valve into my shop that is
> governed by a 4-20 mA signal.
> I have to repair the positioning mechanism.
> No trouble with that, I did it quite a few times on other brands.
> But I do not know what is the standard voltage of the 4-20 mA
> signal for to make a pot-arrangement to simulate the PLC signal.

It is not a voltage, it is a current. As long as you drop at least 6 volts
across the loop, it should work. So, you could take a 9 V battery and
a 180 Ohm resistor in series with a 10 K pot, so you could vary the
total external resistance between 180 and 10180 Ohms. Then, connect
the valve control into the loop, and throw in a DVM so you can read
the current, and you should be able to control the valve. It will be
polarity sensitive, and should have the + and - marked on the
terminals.

Jon