ampmeter wireing

W

waltere

Senior Member
I am wireing the charging system on AV8 and have a question. I am using an Ammeter and I need to be completely certain which wire it hooks into. I think it goes in the armature wire between the regulator and the generator. Is this correct?
Thanks in advance!
Walter
 
The ammeter should be in the wire between the battery and the users and not anywhere between the generator and the users.

You want the meter to show whats going into or out of the battery not how much the generator is putting out in total.
 
Ampere meters are connected in to the buss wiring between the battery and the bus where your fuses or circuit breakers get their power. If it is not an induction type meter but one with terminal connections on the back, a shunt or calibrated length wire is generally used between the main bus feed and the input terminal so that power doesn't go directly through the meter but a good sample of the current flow is taken. Most Fords after the mid 1930s used an induction type that just has a bus wire pass thru a loop on the back of the meter. No muss & no fuss with those.
 
Rotorwrench,
How would you determine the size/ length of this shunt?
I have converted to 12 volts, am running a 6 volt converted to 12 generator/ voltage regulator, I installed an early 1920's or 1930's ammeter out of a Buick I think. It has two terminals and only goes to 20 amps either way. When I rev up past 1500 or so rpm it maxes out. Am I needing this shunt?
 
Ralph Moore said:
Rotorwrench,
How would you determine the size/ length of this shunt?
I have converted to 12 volts, am running a 6 volt converted to 12 generator/ voltage regulator, I installed an early 1920's or 1930's ammeter out of a Buick I think. It has two terminals and only goes to 20 amps either way. When I rev up past 1500 or so rpm it maxes out. Am I needing this shunt?
Click to expand...

It more than likely is. There are purpose made shunts that are like a small fuse block with several terminals but I haven't gone looking for one. On one of the helicopters I work on that is 12-volt, they spliced the main bus wire about half way in its run (the run is approximately 6 feet long). In this splice they also added in a 20 gauge wire for the shunt. The length is calculated by the max output amperage and also figures in resistance of the wire. I know a lot about electrical stuff in order to maintain systems but I am no electrical engineer so I can't help you there with out some further research. A purpose made shunt would be the easiest way to do the job.

Here is a good article about this subject. https://www.bluesea.com/articles/552
It is important to have an amp meter that is equal to the amount of generator or alternator output. A 35 amp system should have a 35 amp meter.
 
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You can shunt the ammeter but it will show the wrong reading.

Measure internal resistance of ammeter add an external resistor of same value and it will show 20A putting thrue 40A

The shunt is gonna take a lot of power so not a tiny resistor a piece of metal with right resistance....

An Ammeter doesnt care about the voltage.
 
Well I am totally lost. I had the Amp Meter wired into the system between the battery and the fuse block, Turned the switch on and it pegs the meter. The shop Forman where I work (big truck shop) told me it should be wired between the A terminal on the voltage regulator and the A on the generator, Is this correct? My generator, voltage regulator, and amp meter are all matching. HELP
Walter
 
Hi there, If you wire it as the shop forman says then the ammeter will only show the generator charge rate. It wont show any discharge of lights or other electrical loads. The correct way is to wire it in series with the main battery feed wire pick up which is on the battery cable side of the starter solenoid and then goes to the fuse box etc. The 20 amp ammeter is a bit small for the later ford generators which can produce up to 33 amps. A shunt across the back of the ammeter will change the meter reading and it will no longer be accurate. Remember when the engine starts up the generator or alternator will charge higher for a minute or two to replace the power taken from the battery by the starter motor during the cranking process. Your ammeter will "peg out" until the charge rate settles back to just a few amps. Some of those early ammeters are a bit over sensitive and tend to give readings higher than actual amps. Regards, Kevin.
 
Only way to trick a small meter into having a endreading i can think of right now is clamping it with a zenerdiode restricting the voltage drop over it .
A zener that size cost money though.
This will just allow the generator to charge more without ******* the meter not changing the reading of the meter.
 
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