nuckolls.bob(at)aeroelect
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 Posted: Wed May 02, 2012 6:13 am Post subject: amp meter |
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At 06:58 AM 5/2/2012, you wrote:
| Quote: | Bob,
I am trying to put together a test rig to make sure my starting vibrator is properly set up after I replace the points and capacitor in both units (twin).
My problem is finding something to indicate amps down in the 1 to 3 amp range. I'm supposed to set the point preload tension such that the unit draws 2 amps at some set voltage.
Everything I've looked at has way to big of a range to be useful.. any ideas would be appreciated. |
I feel your pain . . . and there's a hidden 'rat'
in this woodpile. The current you're attempting to
measure is not a steady, DC current level. It's
'chopped' up in little pieces by the antics of
the vibrator.
Digital ammeters are sampling devices that can
be very confused by a series of measurements that
do not agree closely with each other. What you're
looking for is an 'integrating' or 'averaging'
instrument that gives you some smoothed out value
over time.
Back in the days when shower-of-sparks was the
best we knew how to do, meters fully capable of
setting the system up were also the best we knew
how to do. Typical instruments were the Simpson
260, Tripplet 630 and similar ANALOG multimeters.
The mechanical inertia of the meter needle prevents
it from responding to the intermittent nature of
the current under study and readings were nicely
averaged.
So what you're looking for is an analog multimeter
with a current full scale reading as close as
practical to the currents you expect to measure.
A 5A scale would be nice but 10A or 12A is probably
going to be the best you can do in a multimeter.
The ideal instrument would be something like this
which you can get off eBay . . . if you have time
to wait.
You can get it here for under $10 delivered to your door
but it will take a couple weeks.
http://tinyurl.com/7d3rd25
If you can't find something locally that suited to your
task, I could provide you with one of these little fellers
shunted for say 3A full scale. No calibrated scale plate
but well suited to the task at hand.
Bob . . . [quote][b]
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