7 Function Clamp-On Digital Multimeter

the meter does a fairly good job. the remark about accuracy versus breaker trip is just plain lame. breakers are designed to open when enough heat is generated to trip it and even then there is a plus and minus involved.the correct way is one wire through the meter that is the correct way. 2 or more is just lame since the current can add subtract depending on the current flow direction

Clamp meters cannot be just clamped on an extension cord. You must only clamp on ONE of the wires in the circuit, or your reading will be zero (because the current in the "hot" wire is traveling in the opposite direction to the current in the "neutral" wire, which would cancel the reading out).
It has ABSOLUTELY NOTHING to do with the thickness of the wire's insulation

This is a cheap tester and should be assumed to be such. However, unless you are using it every day, you don't need a >$100 Fluke meter, since this will read just as well.

The opening is very large and can read 2-3 sets of 500 mcm wire, perfect for quick diagnostics.

I'd like to use this product to test insulation but can't find # 261 optional insul. testor!

to Mark the Handymans post; You cant get an accurate amp reading putting a clamp meter over a cord like that... The neutral wire will cancel out the actual current because it travels to your load and then back. its like bending your wire in half and sticking it through the clamp, it wont work. to test it, open up the outlet box and clamp over the hot wire.

Just did some tests with this meter tonight, measuring the current my welding machine draws. I bought the meter for to investigating breaker tripping problems. At low currents (0-30A @ 240VAC) it seemed to be accurate. But as the current climbed, up to 100 amps and beyond, it seemed to overstate the actual current. It read up to 154 amps with the welder full on. That can't be right. The circuit has a 100A breaker on it and it didn't trip. Inconclusive.

I bought this meter to specifically test amps on extention cords. It does not read through the insulation on cords. It has to be very thin insulation to be able to read the amps. I was using a device that pulls 9 amps, and it was reading that it was pulling .3 amps. A little off and Im very dissappointed.

If you want to use the clamp feature to get an accurate reading of AC current, don't waste your time. I would estimate the measurement tolerance to be +/- 35%. The reading varies wildly depending on where the wire is positioned within the clamp. On any decent meter it should provide roughly the same reading, no matter how it is oriented.