Re: [CAD_CAM_EDM_DRO] Why am I still seeing a voltage ?

On Saturday 07 February 2004 05:13 pm, ja_erickson wrote:

> Greetings,
>
> I am in the process of wiring up my controller cabinet and have
> decided to incorporate a servo drive e-stop circuit that
> was created my Mariss of Gecko Drives. In his circuit he has the
> e-stop button disconnecting the "common" side of 110vac. I have
> wired the coolant pumps "common" in series with the "common" from
> the e-stop button so that if an e-stop condition occurs the coolant
> pump will shut down. Ater doing this I started the controller and
> measured the voltages and when the circuit was complete my
> multi-meter showed 117vac, great ,however after I hit the e-stop
> switch I decided to mesure the voltage to verify that it was 0 at
> the coolant pump, To my surprise it measured 17vac.I am not
> accustomed to breaking the "common" leg of a curcuit as my AC
> wiring skills are limited to house things.Can anybody tell me why
> I still see a voltage?

Yes. You don't mention what kind of a meter you're using there, but I'd be
surprised if it wasn't a fairly modern digital type -- with a real high input
impedance, typically 10 megohms. Using such a meter, you'll find voltages
on all sorts of places that you wouldn't expect. Try putting a test light
across the points you're measuring, even with a smallish nightlight bulb or
similar, and watch that voltage disappear.