Close, but no cigar. You're thinking of the way a voltmeter works. A
voltmeter is really a milliammeter with a series resistor. The unit is
connected in parallel with the load. An ammeter is connected in series
with the load. An instrument quality ammeter is usually also a
milliameter, but with a shunt that allows only a very small amount of
current to pass through it - most of the current goes through the shunt
to the load.
So, what to do if you have a voltmeter set up for 12 volts and you want
to read 6? Chances are, it will have a 6 volt mark on it; but if what
you really want is full scale reading at 6 volts, you can get it by
changing the series resistor. Trial and error on the resistor value
with an accurate source or an accurate meter will do the trick, and
you'll also have to recalibrate the dial. So, unless you have nothing
to do with your time, or can't get a proper meter, it's easier to buy
the right range voltmeter.
John
Jay wrote:
>
> Hi, John.
> If I remember how those work, the gauge is simply set to hold the needle
> at a certian level when "x" amount of voltage is passed through it
> (14.5V in a 12V system, I think). Even if you reverse the wires, you
> still are not going to pass enough voltage through to deflect it either
> way. You'd have to get a gauge calibrated to 6V, or get yours
> recalibrated. Either that, or test it with a multimeter to make sure it
> actually IS working correctly, and then just remark the face of the
> gauge to show you where it should be at 6V, regardless of the
> "Charge/Discharge" original marking...
>
This archive was generated by hypermail 2b29 : Thu Jul 05 2001 - 00:40:35 PDT