Re: [CAD_CAM_EDM_DRO] panel meters

In a message dated 3/10/2004 6:56:06 AM Central Standard Time,
nuspel@... writes:
so I am assuming this is for a DC load. <<
Yes.
I was wondering for an AC load are inductive pickups complicated to set up?<<
Assuming what you have in your hands is INTENDED for that, NO! Even simpler
than a DC ammeter setup! The "inductive pickup" you are talking about is a
"Current Transformer", known popularly as a "CT". Those usually look like a
"rubber donut", though small versions that, say, solder onto PC-boards might look
like a tiny mantle-clock with the works removed. You pass the "big wire"
carrying the current you want to measure through the "donut" (CT). That is then
a "one turn primary", and a voltage proportional to the current flowing in
that wire appears between the lead-wires coming out of the CT. This voltage is
measured by a panel-meter which will "read" the amps flowing in that wire
through the CT. In many cases, this "big wire" might be passed through the "donut"
more than once, to DOUBLE or TRIPLE (etc.) the resulting voltage from the
CT's secondary. Sometimes you can spot CT's around the individual power lines
entering an industrial building, say, a good-sized machine-shop. These are
often located overhead, but generally not on the "loose" part of the "drop" that
comes from the pole, but just these wires enter the weatherhead/conduit-down.
There will be smaller (say #14 or #12) wires from each CT (there'd be THREE if
the service-entry is 3-phase!), these leading down to a "box" next to or
right-behind the KWH meter. Connections in that "box" also read the AC Voltage,
and the meter "does the math" and figures what you owe Mr. Edison (or whomever).


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