Ampere meter with internal shunt resistor safe for 30A?

Hi!

I bought the following ampere meter http://www.ebay.com/itm/151314913968?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649.

I thought I would get a meter and a external shunt resistor but I only got the meter. So I think it has a internal shunt resistor (I have seen that meters with external shunt often have a "resistor symbol" and a mV rating).

Is it common to have a internal shunt resistor for a 30A meter? I don't want it to burn up or something :)

It is not common to have an internal shunt for a 30A meter, but it is possible.

Many meters intended for external shunts read full scale when 50 or 100 mV is dropped across the (external) shunt resistor, which in turn will cause a few mA to flow through the meter.

You can test the meter by applying first small and then increasing currents until it becomes clear what the response will be. For example, start with a 9V PP3 battery and a 10K ohm resistor in series with the meter terminals and check the deflection. If nothing happens, try 1K, etc.

Or measure the resistance across the meter terminals with a multimeter…

Thanks, for your input.

I was just abit unsure to put 30A through the meter, the terminals are not that big. Also sent a message to the seller of the meter and he replied that there should be no problem to use it with 30A.

FYI. The listing says it is an internal shunt:

Measure current range of 0- 30A with SHUNT (internally installed) and accuracy of Class 2.5.

Not that I am saying I trust this particular seller or anything like that.

I am quite sure that the extra text came after I contacted the seller :slight_smile:
Yesterday I copied and pasted the “Package Content” text and send to the seller, no "(internally installed) " anywhere.

But it is good that the seller corrected the description.