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I bought an Excel XL 830L multimeter with the understanding that it was a RMS voltmeter.

I also have UEI ElectroMate DM 200.

When I checked the output of my APC unit with both meters, the readings were about the same.

Is there a way to tell if a meter is an RMS type?

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  • \$\begingroup\$ Do you not have a spec sheet from the manufacture that spells out those details? Also DVM's with a true RMS reading will often have that by the AC volts selector switch. \$\endgroup\$ – Sparky256 Feb 3 '18 at 0:39
  • \$\begingroup\$ Do you have a known square wave source? \$\endgroup\$ – jonk Feb 3 '18 at 0:44
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Please see this link :http://www.testequipmentdepot.com/uei/digital-multimeters/dm200.htm

The meter is a discontinued model also available from Ebay. It is NOT a true RMS meter so non-sine waves will give a ambiguous reading at best. Usually a non-RMS meter will see only the most peak voltage present and not the true average.

If you want an excellent true RMS DVM stay with a known good manufacture like Fluke. The Fluke 87 III series is $400 USD, but it is top dog for accuracy.

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  • \$\begingroup\$ So, this is probably a non-RMS meter? walmart.com/ip/… \$\endgroup\$ – fixit7 Feb 3 '18 at 2:36
  • \$\begingroup\$ The link looks like a good choice. The difference between a good RMS meter and a great one is long-term stability. How accurate will it be 5 years from now. Fluke uses EEPROMs for long term storage of calibration values due to aging and extreme temperatures. The TEK DVM for $34 USD would be lacking such expensive add-ons. \$\endgroup\$ – Sparky256 Feb 3 '18 at 2:55
  • \$\begingroup\$ I always scratch my head as to why you'd want a $400 dollar RMS DVM. The mains is a sine(ish) wave so any meter will measure it. 400 bucks will get you a decent Rigol oscilloscope that can measure any non sinusoidal signal you can reasonably imagine. So? \$\endgroup\$ – Paul Uszak Feb 3 '18 at 3:10
  • \$\begingroup\$ @PaulUszak Because I used them at work a lot. I have a cheap Fluke 77 for myself. \$\endgroup\$ – Sparky256 Feb 3 '18 at 5:54
  • \$\begingroup\$ @PaulUszak. The mains might be clean AC but I have used them to measure the output of the many UPS's that I have for my computers, stereo's and TV's. They have a lumpy output at best, which is why APC recommends you do not drive motors or large inductive loads with them. \$\endgroup\$ – Sparky256 Feb 3 '18 at 6:12

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