GTC CM100 1 mA to 100 Amps AC/DC Low Current Clamp Meter by General Technologies Corp

Great milliamp meter for DIYing a vehicles electrical system/battery drain. Measurements are consistent and accurate. Easy to use. Money well spent!

This meter is easy to use and works well. Happy with my purchase!

Perfect to find parasitic power draw for automotive trouble shooting. The only thing that would be great that could be added other than the peak, and hold function would be a DC averaging function. Where it not only records the highest value but average as well.

Seems to do what it's supposed to do. The function "Thumbwheel" is pretty darn stiff, as compared to a couple of Mastect's I have here .. I guess that's a good thing, depending on your preference .. turning it On may be a two-hand operation .. depending on your manual dexterity and digit strength. It lacks an LCD back-light function, or a "Target" LED. The "Volts" screen-printing should have been done in a more contrasting color .. this is a "Mature" product, but this has still been neglected.As typical with all Hall-Effect devices, it has difficulty in discriminating between what would be a True RMS (pure D.C.) current, and any residual A.C. component from an A.C. powered battery charging system, so it kinda goes a little nuts when my inverter/charger is pumping through 70 amps (56 volts during bulk). Most accurate readings are found during discharge, with the PV panels Off, to avoid any A.C. ripple from the charge controller. It will clamp nicely over 2 gauge welding cable, but you will need to remove a short length of insulation from 00 gauge for it to fit over the cable .. re-cover with thin electrical tape. This meter will accommodate maybe 95% of my current measuring tasks .. everything but engine start and glow-plugs .. the Mastec's linked here are good for 600 amps. Although a bit pricey, I do recommend this meter for both Off-Grid systems, and automotive diagnostics. Cheers!Mastech MS2108 True-RMS AC/DC Clamp Meter with Inrush Current Measurement

This meter is slightly temperature sensitive. If you leave it on for 2 - 3 minutes and re-zero it, it will not drift more than 1 ma. If you pick up the meter it will drift from the heat of your hand, if you put it back down, it will return to 0ma. So I hold the meter for a few minutes, re-zero and take the measurement, it will drift almost nothing. If it does, just subtract the drift from your reading. Take into account the sign of the drift. I have a few other expensive meters that do the same thing at very low ranges and use them as I described above. Even very expensive other meters will drift at very low ranges whether they measure capacitance, inductance, milliohms, or field strength, volts/amps/resistance or whatever.This meter is so sensitive to extremely small magnetic fields that spacial orientation to earth's magnetic field affects these kinds of meters. Zero the meter near the measurement location, move the meter to attach it around the wire, but don't change its spacial orientation by twisting, rotating it, just move it forward to the wire. It would be better to hold the meter close to the wire, zero the meter, then hold meter still and move wire to jaws.Use this meter with common sense, and it will work very well.

Very accurate down to 1ma level.When measuring the DC current combined with peak function, you need follow the current flow direction mark on the clamp side, if flow direction reversed, then you will always get "0" as peak value because the real peak value is recorded as negative,then you will think the peak funtion is not working.( this is also true for dc vlotage measuremet with test lead)Its response time is quick.The zero function work fast and accurate.Only one issue: the DC voltage measuremet get 0.2 volt difference (less) in negative reading if you reverse the two test leads to measre.(like 1.5 v and -1.3 v which shouel be -1.5 v) I tried two meters and they act the same. I may live with this and remember to keep the low DC voltage measurment in positive side. Amazon even send me the new second meter before I return the first one.Definitely a great buy, if you wnat measure low accurate dc or ac current with clamp, and need peak function.

I have several clamp on meters for dc measurements that are bad to awful, the last being a General Technologies CM100. My CM100 measured voltage with an error, has now stopped working for DC current, was unstable in measuring DC current when it was working, and had a small hole for the cable limiting me from measuring my inverter current in a 4/0 cable. I just bought a Voltcraft Current Clamp Meter VC330 (a German instrument) that feels well made and so far is working great at less than 1/3 the price. The VC330 will clamp on a 4/0 cable.

I never heard of this company, but they are based out of Canada. Figured how bad could it be.The fit and finish is great. I like the resolution of this meter. I will use this for automotive current draw.The wire opening is really small, probably how they can get good resolution and increased accuracy.LCD is easy to read and it has Min/Max function.