Radio Shack SPL meters are damn accurate.
My boat came with a panel mounted digital DC volt meter that reads to .
1
I had a Fluke 187(some crackhead stole it!) that read to .001 and also
read AC on DC so I could see the ripple making it thru the rectifier
on AC Charge. It was fun to watch the voltage come up by the
thousandth.
The panel meter is .2-.3Volts low and is quite upsetting when it says
my 900AH golf cart bank is at 12.0 when It's in the high 12.3 with a
10 amp draw....

My problem with "dispose-a-tools" is that they need to be disposed of
at the most inconvenient times, when you are contorted into a tight
corner having spent a half an hour setting up a 2 minute job they
validate murphy and fail. argggh

Larryr wrote in news:422276b1-0f4b-4462-8db5-
:

The panel meter is .2-.3Volts low and is quite upsetting when it says
my 900AH golf cart bank is at 12.0 when It's in the high 12.3 with a
10 amp draw....



If you would remove the panel meter and take it to a calibration shop that
does analog meters, they will put it in a magnet charger and put an
accurate full scale voltage on it. Then, they will pulse the magnet
charger to bring the meter's permanent magnet up to proper magnetic field,
making the meter read correctly. They will track the meter and if the
tracking from full scale to zero is out of tolerance, they can rescale the
meter scale to read correctly....for more money, of course.

If you tell them you want the meter to be dead accurate at some point on
its scale, say 14.2V for accurate charging, they can calibrate the magnetic
field at that point, instead of full scale.

They'll also test the D'Arsonval's movement jewelled bearings and set the
tension on them, which will have slackened over its lifetime, and make sure
it has the right hairspring tension for good tracking. The hairsprings
slacken tension over their lives, making the meter too sensitive and
spreading the scale inaccurately.

Sure is cheaper than a new, also inaccurately calibrated, meter.

If you're near Houston or Virginia Beach find EIL Instruments and give them
a call. I used to be their mobile calibration van manager, dragging an
office trailer across the country repairing and calibrating CG and FAA test
equipment, on site. Both places had meter calibration facilities to
support commercial and military shipping panel meters, which are still in
use today.

Larry, the panel meter is a no name digital meter. I would rather
take calibration service money and put it towards a battery monitor
system like a link 1000, although I have gotten by without such so
far. Thanks for the info nonetheless.

Larryr wrote in news:b9dee785-7855-441f-933a-
:

Larry, the panel meter is a no name digital meter. I would rather
take calibration service money and put it towards a battery monitor
system like a link 1000, although I have gotten by without such so
far. Thanks for the info nonetheless.


I bet there's a little tiny pot in that kind of meter to calibrate it.
Probably has some fingernail polish holding it fast. Put a known
CALIBRATED meter across the terminals on the back and just adjust the pot
until it reads the same 13.8327 volts the calibrated meter reads.

DVM's aren't rocket science.

Shhhh...don't tell anyone, though. I made quite a comfortable living off
them for many years.....(c;