Ammeter question . Can I damage my ammeter

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Oscarpop

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We have some of those little analogue ammeters fitted to measure current.

One of them is rated to 10amps, or rather the needle can go up to 10 amps.

My question is, if I ran more current than this through it, would it damage the ammeter?

I am happy to accept that it will simp,y register at 10 amps , but I don't want to damage it.

Many thanks
 
It might take some excess current OK, but it's very much dependent on the individual meter. I wouoldn't think it would be wise to put more than say 15A through it.
 
+ 1

The manufacturer is the only one who can say how much overload they will withstand ~ ~ ~ ~ ~ ~ ~ ~ but probably won't!
 
Oscarpop said:
One of them is rated to 10amps, or rather the needle can go up to 10 amps.

My question is, if I ran more current than this through it, would it damage the ammeter?

I am happy to accept that it will simp,y register at 10 amps , but I don't want to damage it.

Many thanks
Click to expand...

Depends on shunt operation, some us the magnetic field, passing the power cable behind meter located by a clip, should be okay on overload say 2 or 3 times load.

Meter with shunt, internal or on meter back and remote mounted, meter should be okay, but shunt may be damaged and risk of a fire.

All a matter of ammeter design shunt design.


Brian
 
nigelmercier said:
However, there is no such thing as an ammeter.
Click to expand...

The cheap ammeters I saw fitted to vehicles when I toyed with such things were basically moving-iron with a hefty coil of 2 or 3 turns taking the full current. No shunt anywhere. The OP's might well be similar, in which case they will withstand quite some overload, but I'm not recommending that!
 
nigelmercier said:
I wouldn't risk it. However, there is no such thing as an ammeter. What you have is a shunt and a voltmeter, so the range can be increased with a different or parallel shunt.
Click to expand...

I beg to differ. All analogue meters, just about, are ammeters, because they use a magnetic field, produced by current, to move the needle. The shunt simply makes sure that it is only measuring a suitable fraction of the current in question. Analogue voltmeters measure the current through a fairly high series resistance.

As it happens, I have a true mechanical voltmeter in my collection. It uses the electrostatic attraction/repulsion between two plates to move a needle. Range is set by changing the initial spacing, and goes up to 40kV.

Digital meters are all voltmeters, deep down.
 
I have an old analogue ammeter where the needle bottoms at 30 A. It is shunt based, two shunts on the positive side for house bank/starter battery and a change-over switch. My alternator is 70 A, so when I start the engine with anything but a full house bank the meter will bottom out for a while. I have not noticed any problems, for instance the shunt getting hot.
 
As said the amp meter is likely to be the moving iron type with all the current going througha coil of about 3 turns of heavy wire. You are not likely to damage this with 100% or more overload. However the needle mechanism can be damaged by excessive force against the stops. A rapid increase in current is worse for damaging the needle. In my younger days I was for ever opening up meters to straighten the needle bent by overload . MMore with moving coil type.
Assumming all current goes through your amp meter you can make a shunt for it from a piece of stainless steel sheet. Cut it in a curved shape so the ends can be bolted down under the terminals of the meter. You will find for a given current, the indication will be reduced by a percentage when the shunt is attached. You can then calculate the change of reading so adjust your understanding of the measurement.
The shunt of SS can be made more resistive so less reduction of reading by cutting the metal between the terminals narrower or using thinner sheet metal. Or you can use a piece of ss locking wire and adjust the length to give the effect you want. Much easier to adjust. Start with 10 cms of 18g.
Note must be stainless steel to give resistance although iron fencing wire is Ok but would need a lot more wire.
You want to make the meter read 0 to 20 amps not 0 to 10 amps. So a shunt across the meter terminals will mean only half the current goes through the meter and is measured. If you are careful you can remark the meter dial to indicate 0 to 20 amps. All a bit fiddly.
To answer your question probably no damage to overload the meter. good luck olewill
 
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