Farmall Cub

Is there anything special about an amp guage for a 6 volt pos ground system, or will any amp guage work?


Tom

Short answer, generally no difference except the range with in which the gauge reads the amps. Some of the newer amp gauges are negative ground specific.

For a 6 volt system, a gauge reading a maximum of 20 amps would be satisfactory. A gauge with the ability of reading 60 or 120 amps would work in an electrical system capable of outputting 20 amps or less. However, the ability to get a near accurate reading from the gauge will be severely hindered.

Thanks Eugene. The "negative ground specific" rings a bell and that's why I asked the question.


Tom

I bought a generic 60 amp gauge recently at napa. Works fine. Its a little deeper than the original, so it makes space a little tighter behind an already tight dash, but it works. I cant really figure out how an amp gauge would be polarity specific....it simply reads the current through the current carrying conductor of the system. It is, in fact, part of the conductor. If it reads a discharge while charging, it would simply be a matter of reversing the leads on the gauge.

There's nothing specific about the ground type on an ammeter. Ammeters are not grounded (for the ammeter function).

If your ammeter is lighted, it is, of course, grounded. But, the Amp-measuring part is not grounded.

The basic ammeter I typically see is not polarity dependent. There are shunt meters which may be what Eugene is talking about. They are just a low ohm resistor and a voltmeter calibrated to read the voltage drop as current. They may be ground polarity dependent.

Thank you all for your input. I'll check out some parts stores and see what they have, or order from Steiners.


Tom

twotone wrote:Thanks Eugene. The "negative ground specific" rings a bell and that's why I asked the question. Tom

They are not too common, but there are a couple of companies that decided to get fancy. A normal ammeter has a shunt (high current resister of a known value) inside it connecting between the 2 terminals. The meter is actually a low voltage voltmeter that measures the voltage drop across the shunt, and the scale is marked to correspond to the amount of current flowing to cause that much voltage drop. There are some electronic ones that instead use a coil of wire wrapped around a conductor that is connected between the 2 terminals and an electronic circuit to measure the magnetic field induced, and the circuit drives the meter. those are negative ground specific, and the circuit will not work with positive ground.

Thanks for that explanation John. I checked a few parts stores today and all they had was volt guages. I'll order from Steiners as they have 2 amp guages that are listed for a Cub.


Tom

Our local Carquest stocks these, note, the picture is not correct. They give a discount, price is around $20 to $25.
http://www.carquest.com/webapp/wcs/stor ... acesApp=0#

Thanks John. There's a Car Quest on the way to my wife's work.


Tom