AC only or AC/DC Clamp Ammeter?

Get the right meter for testing your RV electrical system…

Mike, I really enjoy your entries in the RV Travel newsletter. They are very informative. Some time ago I think I recall you making a recommendation of a clamp meter for RVers. I would like one that measures DC current in 12-volt systems. Can I bother you for a recommendation? —Bill

Hey Bill,

Most certainly…. As some of you may already know, an AC clamp ammeter uses a tiny current transformer in its jaws to measure amperage.

However, transformers only pass Alternating Current (AC) voltage and current, so that technology can’t measure DC amperage. That’s why an AC clamp meter is only useful for measuring AC current. And that’s a problem if you want to measure the DC current for your battery system.

Enter the Hall Effect Sensor

More expensive clamp meteres use a Hall Effect Sensor instead of a current transformer. This semiconductor device can measure either AC or DC current, so you can get a clamp meter that will measure both 120-volt AC shore power amperage, as well as 12-volt DC amperage in your RV’s battery system.

Expect to pay a little more for a clamp ammeter with a Hall Effect Sensor that performs both AC and DC current measurements, but the flexibility of having a tool that will work for both AC and DC troubleshooting in your RV is well worth it.

I use the The Southwire 21550T in my seminars

Here’s my go-to clamp ammeter for RV electrical testing. The Southwire 21550T does AC or DC clamp testing as well as voltage and resistance/continuity measurements.

Plus this is also a True RMS meter, which means it can calculate accurate values for voltage and amperage with distorted waveforms. And it includes a Non-Contact Voltage Tester function, which can be used for hot-skin voltage testing.

The Southwire 21550T is a great clamp meter that’s reasonably priced and available at any Lowe’s store or on Amazon HERE.