There might be some other solutions to installing an ammeter without
running hefty cables around. An ammeter is just a millivoltmeter with
a calibrated short across it. The meter measures the voltage drop
across a known resistance and this voltage is proportional to the
current flow. So you could install a millivoltmeter across an
existing section of wire to measure current. It doesn't even really
have to be calibrated since all you want to know is what the current
is normally and when it's non-normal. So you connect the meter across
a section of wire, then adjust the sensitivity of the meter so that
the readings don't go offscale (using a small variable gain amplifier
or perhaps just a potentiometer) and you have an ammeter. If
you want to you could even calibrate it using another ammeter
but most ammeters just read +/- 60 anyway so there's no real need to
do this. In this way, the wires going to the ammeter can be ordinary
small gauge wire. A circuit that would probably work would be:
_______
| | +/- reading millivoltmeter
| | |
|__|__|
| |_______________________ to one end of existing section of wire
| /
| \
| / potentiometer
-------------->\ (10K - 10turn pot)
/
\____________ to other end of existing section of wire
The wire you want to connect it across would be some section of the wire that
goes from the alternator to the battery; whatever is easily accessable.
Another way might be to use the same principal used in clamp-on
meters to measure current. In that case you wouldn't even have to
connect any wires to the starter/charging system.
Ron
ron@vicorp.com or uunet!vicorp!ron
|