Ammeter - Yes Or No

[Guest Jameslark]

I have already got fitted a voltmeter and have been given an ammeter. I think they basically do the same job and that to have both fitted would be merely duplicating a reading. Am I right?

If I am I will then be willing to sell it on to anyone here who needs one for £10 plus postage. The item is brand new made by TIM with black face and still in its original box. So either I fit or someone gets a bargain as I hate things just lying around gathering dust.

[harvs]

I think they basically do the same job

 

Nope. The ammeter measures current - ie how many amps are being drawn and the voltmeter (surprisingly!) tells you the voltage.

 

The voltmeter can help to tell you how well the alternator is performing

The ammeter can tell you if you've got a lot of electrical things turned on (or maybe indicate a problem)

[Guest Peter Kelly]

I have already got fitted a voltmeter and have been given an ammeter. I think they basically do the same job and that to have both fitted would be merely duplicating a reading. Am I right?

If I am I will then be willing to sell it on to anyone here who needs one for £10 plus postage. The item is brand new made by TIM with black face and still in its original box. So either I fit or someone gets a bargain as I hate things just lying around gathering dust.

They do not do the same job. The ammeter will tell you if the battery is being charged or discharged in real time.

The voltmeter will tell you what voltage is available. I think the ammeter is of more use than the voltmeter. It will also tell you if the charging system is working correctly.

 

Peter

[Guest Peter Kelly]

I have already got fitted a voltmeter and have been given an ammeter. I think they basically do the same job and that to have both fitted would be merely duplicating a reading. Am I right?

If I am I will then be willing to sell it on to anyone here who needs one for £10 plus postage. The item is brand new made by TIM with black face and still in its original box. So either I fit or someone gets a bargain as I hate things just lying around gathering dust.

They do not do the same job. The ammeter will tell you if the battery is being charged or discharged in real time.

The voltmeter will tell you what voltage is available. I think the ammeter is of more use than the voltmeter.

 

Peter

[Snapperpaul]

With a good battery and a good alternator I found in the past that an alternator does not move much at all.

I find a voltmeter useful as I can see if the alternator is within operating range 13.2 to 14.8 ish

[Guest Jameslark]

I didn't explain myself very well as I was aware they of course do measure amps and volts. Rather I cannot see the point in installing an ammeter if one has a voltmeter already fitted. The voltmeter, if not "in range" gives a clear indication there is a problem. Just didnt want to put it in for the4 sake of it.

[Grim]

i see where you're coming from! They both give information on whether the battery is being charged or discharged.

 

A volt meter will read above 12.7v if the battery is charging and below if discharging (using more than you can generate).

An ammeter will read a positive value if charging and a negative value if discharging, with the disadvantage that you have to run all your electrical load through the gauge.

 

Personally I'd stick with the voltmeter and wouldn't bother with the ammeter.

[megadodo]

Voltmeter, definately. An ammeter WILL NOT tell you the battery voltage, it's all very well having a charging current but if the battery is not taking charge what's the point? Voltmeters are far more indicative of good electrical health. The other plus point is you dont need all the heavy duty wiring that Stewart was talking about all of which increases the overall battery cable length and causes unwanted voltage drop. You can also wire the voltmeter (through an additional push button switched circuit) to read the battery voltage with the ignition off if you want. If you're charging you should see 14 volts on the meter. Most ammeter setups don't measure the starter current draw anyway whereas the voltage drop off during starting can show any issues very nicely.

[Guest Jameslark]

Looks like it going on fleabay then. Thanks for all the good advice one and all and backed up my suspicions.

[Guest chris brown]

Voltmeters are normally used in conjunction with an alternator and a ammeter with a dynamo also it is not true that heavy wires have to be coupled to the meter as they are normally miliameters and are connected between the output of the alt/dynamo and the battery and uses the thick wire as the shunt (a bit of a fiddle getting correct resistance shunt to get accuracy in the meter). Ford did this on the Capri but it does mean that all circuits have to be powered from the alt end of the battery to alt wire unless only charge rates are indicated

[megadodo]

Well explained Chris, all the ones I've seen in kits or other aftermarket scenarios must have been cruder affairs then as they tended to be wired straight from somewhere in the engine bay (usually interuppting the main battery supply to the internal electrics but not the starter supply) with wires of very large diameters. Having said that I never inspected them closely enough to check for "shunt" wiring. One chap I knew lost his car in a fire when his ungrommeted ammeter wiring shorted on the bulkhead! (not that this was the ammeters fault!) I still think a voltmeter is more indicative though!