Re: Why am I still seeing a voltage ?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Roy J. Tellason"
<rtellason@b...> wrote:

> 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.

thanks for the reply,

i attempted that feat using a small bulb and it didnt light.
is there an actual voltage present or are those meters incorrect?
another interesting thing i noticed is when i break the "hot" leg
instead of the "common" ,the voltage is 0, kind of like what i
expect to see.can you tell me why this is?

thanx
jeff