In the Know: What is True RMS?

What is True RMS, and why would you need it? Watch this video where we talk about what True RMS is and why you'd need it in your multimeter or clamp meter.

• Category

  Science & Technology

[Paul Lum]

Hi, I need to measure the AC current coming from Enphase microinverters that are connected to solar panels on my roof. Do I need a true RMS clamp meter for this application?

[extechvideos]

Typically whenever you're dealing with AC that has been converted from another source, it's not a pure sine wave like the AC that comes into your home.

So I would think that you would need a True RMS meter. For example a UPS that would keep your PC operating for a time if the power went out is not a real AC sine wave and would require a True RMS meter to measure AC correctly.

[TheDustikus]

I know this video is quite old at this point, but in the market for a new meter and from what this video is telling me, if i'm not working with AC voltage it's pointless? I'm an auto mechanic so all I ever really see is DC voltage, someone point me in the right direction? Thanks.

[extechvideos]

True RMS applies for AC Voltage and Current measurements, but not DC. True RMS isn't something that applies to what you are measuring. Thanks for your question! Feel free to check out extech.com for some ideas for meters!

[Vaughan Carter]

I'm not knocking Fluke because I like their products, but just because something looks pretty or nice doesn't mean it'll do the job. If the meter isn't tested, category III or better, and stamped with the official C (UL) US mark on it then I'm not going to pay it any mind anyway, regardless of how pretty it is.

[frequencydrive]

Those Extech meters are so ugly! They need to hire designers to make them look nicer. Look at Fluke. They make nice shit! Designed so well.

[mjmonjure]

Nice video, always wondered what that was, thanls

[extechvideos]

if you watch around 1:30, you'll see that the video states True RMS Multimeters use the Root Means Square Formula to calculate a more accurate reading. There are a lot of articles online that go more into the math behind how a meter does this, but we wanted to make an introduction to how it works, and why you'd need a True RMS Capable meter. Thanks for your question!