Why Do People Believe Cheap Digital Volt Meters?

[MisterEd]

A small rant...

Why do people believe that digital volt meters are always right on? A cheap meter can easily be several tenths of a volt off. You have to pay a lot more than $10 or $15 to get one that has voltage readings that are close.

Inaccurate measurements can lead to false security. For example, suppose you adjust your "low" 3.3 volt rail from 3.2 to 3.35 volts using your $10 DVM. The real change might be from 3.35 to 3.5 volts! Does that sound like an improvement? Of course this assumes your voltmeter is reading low. It could be reading high. The only way to know would be compare its readings with either a voltage standard or a known accurate meter.

Cheap digital voltmeters have their uses for monitoring voltage changes and general measurements but should not be relied on for accurate electrical measurements.

Also, see my comments on meter accuracy at the end of this thread:
http://www.ocforums.com/showthread.php?s=&threadid=299338

[computerpro3]

uh i see your point but the fact of the matter is with psu's several tenths of a volt isn't much....

3.35v to 3.5v is DEFINETLEY an improvement, especially if you do mods. Look at my system in my sig. I run my voltages

3.3 @ 3.7v
5v @ 5.3v
12v @ 12.5v

Trust me, all those voltages are over their spec, and help with the vmods.

If I had the cash though, I would definetley go for a fluke...


good advice though.

[Oklahoma Wolf]

Originally posted by MisterEd
Cheap digital voltmeters have their uses for monitoring voltage changes and general measurements but should not be relied on for accurate electrical measurements.

Beats Motherboard Monitor and other programs that rely on the motherboard's own mostly inaccurate hardware.

However, I do agree some cheapo meters do lack in accuracy. It's not necessary to spend a fortune on a Fluke for simple voltage verfication at the PSU, but neither should the cheapest things out there be counted on to be completely accurate. Two of my own meters were each over $100, and one was a cheap Radio Shack... the good meters blow away the RS for accuracy, but the RS is still good in a pinch for something simple like non critical voltage verification (I just don't use it for repair jobs where I need the accuracy).

[JimmyG]

It is very easy to determine how accurate the cheapo meter is. Find yourself a friend that has an expensive meter and compare the two on a voltage source. Then, add or subtract the difference noted when you use the cheapo. Usually, even the cheapo meters don't drift much.

[Nebulous]

This post swings both ways.

I agree: because certain cheap DMM's are not 100% realiable, I can vouch for that myself;

Yet I disagree: because the $14 DMM i got from Radio Shack is about 98% reliable. I borrowed a friend's $200 DMM and compared them both usng the same psu. I would say the both DMMs were right on the mark, but the $14 RS DMM was off by about 0.0001v which is close enoguh for me.

Now one thing i don't rely 100% on is the bios readings and MBM5 for voltages.

But this post does make a very good point.