Re: Need Panel Meter

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi James,

On 7 Aug 01, at 6:05, Tesla list wrote:

> Original poster: "James T by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jamest2000-at-att-dot-net>
> 
> Brent,Greg,Mike,All,
>  Current transformers are about the safest way(IMO) to measure current in a
> control box.
>   My experience is that you can't use just any amp meter with the current
> transformer. The
> "real" ones I saw had "current transformer" on the front panel in tiny
> letters. When I tried to
> use a standard panel meter I had non linear readings. Mabey the meter
> loaded the coil up to
> much.

That's probably because the CT requires a defined resistive load. 
Knowing R, you can measure V across it to I. Direct correspondence. 
However, it takes no account of waveforms other than sinusoidal.

Regards,
malcolm

>  The official meters were very pricey. If anyone knows how to use a cheap
> analog Amp meter with
> the many choices of cheap surplus current transformers, me and many others
> would love to know.
> Regards,
>  James
> 
> 
> Tesla list wrote:
> 
> > Original poster: "Brent Turner by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <bturner-at-apc-dot-net>
> >
> > Use a current transformer. For example, to meter 50 amps, get a 50:5
> > transformer and use a 5-amp meter. Scale factor is multiplied by 10. You
> > should be able to find surplus AC current meters like that in surplus.
> > Transformers are fairly low-cost as well, and also available in surplus.
> >
> > This is what I used on my controller, though the meters I used weren't
> > cheap. (Looks fantastic though.)
> >
> > - brent
> >
> > Tesla list wrote:
> > >
> > > Original poster: "Mike Waddick by way of Terry Fritz
> > <twftesla-at-qwest-dot-net>" <Mikew-at-winternet-dot-com>
> > >
> > > greg,
> > >
> > > I looked all over for pannel meters and boy do some people want ALOT of
> > > money for them, i belive digikey wanted 50-60 dollers EACH!!
> 
> snip
> 
> >
> > >
> > > Mike Waddick
> 
> 
> 
>