dc amp meter question.

[poolman966554]

hello all.

i was considering purchasing a DC 5A meter here.
http://www.ebay.com/itm/US-Analog-A...698?pt=LH_DefaultDomain_0&hash=item51b3278952

the image shown on the right side of scale..does that say -2.5 ohm?

is this the resistance i must account for with meter in series? If so, whats the since if you have, say a .5 ohm resistor?
That seems like you cant check your math with an additional 2.5ohm addition

I also saw a few digital amp meters, but required a power supply. ill buy one if it has a "no-load" feature.

can anyone clue me in here? thanks

 

[DIWdiver]

No, that doesn't say 2.5 ohms. If that were the resistance, the meter would melt at 5A (67.5W)

The only practical 'no-load' current meter is a clamp-on type like this http://www.ebay.com/itm/NEW-Southwi...171?pt=LH_DefaultDomain_0&hash=item461612d70b

Or this:http://www.ebay.com/itm/Triplett-93...069?pt=LH_DefaultDomain_0&hash=item19e4ecb74d

Or this: http://www.ebay.com/itm/Klein-Tools...419?pt=LH_DefaultDomain_0&hash=item3cd889e0e3


The Triplett is a cheap Chinese thing, the Southwire is probably better, but I couldn't find much on it, and the Klein is a good one. It sells for $125-160USD. When shopping, be VERY careful to get one that reads DC Amps with the clamp. The vast majority, especially of the inexpensive ones, only read AC Amps. There's also a Klein CL1000 that reads DC uA through the wire leads only.