Re: [CAD_CAM_EDM_DRO] panel meters

Have a look at http://www.mpja.com You can also have a look at
http://www.digikey.com Digital meters there start at $35, analog
meters start at about $50.

Most of the meters you encounter will be 0-200mvDC, so you'll need some
precision resistors to divide down your input voltage, for example, 900
000, 90 000, 9 000 ohms and 1 000 ohms in series. Connect the meter
across the 1 000 ohm resistor. The voltage displayed will be 1/1000 the
input, i.e. 200V in will put 200mV across the meter.

As far as current, you'll need a very low resistance, precision
resistor to put in series with your power supply and load. Scaling is
similar to above. E.g. You have a 0-200mV meter, and you want to
monitor 0-20A. So, we know we want 200mV out for 20A current, so:
.200
------
20

Which would be a 0.01 ohm resistor. (such as Digikey # 15FR010-ND) So
you would put the resistor in series with the supply and load, and
connect the meter across the resistor. Negative on the meter goes to
the more negative side of the resistor.

One more thing, most of the digital meters have to have a supply
separate from the one they're monitoring. So, for example, you can't
use +5V from a regulator connected to the (say) +35V supply you want to
monitor.

Regards,
JJ

On Tuesday, Mar 9, 2004, at 09:06 US/Eastern, plastiguy wrote:

> Group -
> I'm seeking smallish panel meters (2"x3" or so) to fit to my power
> supply for 3 Geckos driving DC servos. Need both voltmeters (0 to
> 100 or so) and ammeters (0 to 25 or so). Any leads?
> Thanks
> Scott
>
>
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