True Rms Multimeter
Advantage of "true rms" multimeters?
For the newbie over here, what is the advantage of using a true rms multimeter, over a regular multimeter that you can buy for $20?
I take it that true rms is a lot more accurate than the cheaper meters?
The RMS value of an alternating current is also known as its heating value, as it is a voltage which is equivalent to the direct current value that would be required to get the same heating effect. For example, if we applied 120VAC RMS to a resistive heating element it would heat up by exactly the same amount as if we had applied 120V DC.
Waveforms that are NOT Sinusoidal or DC need a precisely calculated conversion constant depending on the shape of the waveform. Meters that are of the simple nature are Average reading meters which have scale correction factors that assume the waveform is either Sinusoidal or DC. They do not read correctly with other waveforms. The term "accuracy" is not quite correct as such meters respond quite accurately to the waveforms, they just do not return the result you expect.
If you never have to do measurements on odd waveforms, then you will not need a True RMS meter. If you are good with the maths, you also can, by calculation, know what your meter should read and so will not need the True RMS meter. However, if you don't fall into either of those categories, the True RMS meter is worth the extra money.
A look at what is currently available on eBay
 Fluke 87V Industrial True RMS Multimeter with Temperature US $350.00 
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 Fluke 177 True RMS Digital Multimeter with Backlight US $94.00
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 Fluke 179 True RMS Digital Multimeter Combo Kit US $150.00
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 FLUKE 87 V TRUE RMS MULTIMETER US $132.50
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 FLUKE 87V TRUE -RMS MULTIMETER WITH TEMPERATURE . T-12 US $152.50
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 FLUKE 87 V TRUE RMS MULTIMETER WITH LEADS - NICE!! US $149.99
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 Fluke 87 V True RMS Multimeter New US $107.50
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 Fluke 87 V True RMS Multimeter In Fluke Carry Case With Fluke Leads US $149.99
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 NEW Fluke 179 True RMS Multimeter US $129.99
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 Fluke 79 III True RMS MultiMeter with Positive lead US $.99
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 FLUKE TRUE RMS MULTIMETER LIKE NEW MINT CONDITION US $36.00
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 Mac Tools EM700 True RMS Multimeter Digital Multi-meter @ US $24.99
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 FLUKE 177 TRUE RMS MULTIMETER NO RESERVE!!! US $61.00
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 Fluke 177 Digital True RMS Multimeter with leads. US $199.99
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 Fluke 336 True RMS clamp meter Used .99C with no reserve 336a Multimeter US $31.00
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 FLUKE 87 SERIES III TRUE RMS MULTIMETER w/ fluke case/manuals US $102.50
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 FLUKE 113 TRUE RMS MULTIMETER US $60.00
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 Fluke 177 True RMS Multimeter US $64.99
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Items recently purchased from this site
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LCD display. Tester. Tool. USB,
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