Hi!
Working on another six volt tractor--this time a completely restored Allis Chalmers WD...
I have found the existing ammeter has somehow gotten water inside. This has rusted and damaged the meter movement beyond any repair I can perform.
What I'm looking to know--does an ammeter have a voltage requirement? Or could I use a modern (and presumably 12 volt) replacement ammeter without any issue? Even if the reading was "low by half" that would be fine.
William
amps are amps, regardless of volts
I've worked on a lot of tracor electrical's, and NEVER seen an external shunt on the ammeter
An ammeter is just a low voltage voltmeter reading the voltage drop across a low resistance shunt resistor. Usually just a brass or copper strip. You should measure the resistance of the shunt on the tractor and make sure your new ammeter is designed for that shunt resistance. Or buy an ammeter with the shunt included and use the new one.
Garrett Fulton
I'd get a new shunt that's designed for the new ammeter. The shunt is just a low voltage resistor, usually a copper or brass strip, that creates a small voltage drop, (as a function of current flow), to be read by the ammeter. The ammeter is just a low voltage voltmeter. The shunt resistance has to be what the ammeter is designed for or it will be inaccurate.
Garrett Fulton
Some of them have the shunt internally in the meter case. I would think this older tractor has an external shunt. My old Massey Ferguson does.
Garrett Fulton
"William R. Walsh2" wrote: > Hi! > > Working on another six volt tractor--this time a completely > restored Allis > Chalmers WD... > > I have found the existing ammeter has somehow gotten water > inside. This has > rusted and damaged the meter movement beyond any repair I can > perform. > > What I'm looking to know--does an ammeter have a voltage > requirement? Or > could I use a modern (and presumably 12 volt) replacement > ammeter without > any issue? Even if the reading was "low by half" that would be > fine. > > William
A 12 volt ampmeter will work just fine. Those kind of gauge are not voltage dependant. BTW I have a JD 40U that is near mint.
While this is mostly true, how the amp meter works has some effect on were it can be used. A shunt type meter is some what voltage sensitive (not with the range we are dealing with here) because of a voltage drop they can induce plus if a shunt type on has a .05 ohm internal resistance, It will drop voltage voltage 1 volt with a 20 amp load which can be a problem as voltages get lower. With clamp on style that measure current by magnetic field density, this is not a issue.
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