Voltmeter

10.

(Possibly less, but not guaranteed.)

It's a question the voltmeter manufacturer might address over the telephone.

What question number is that?

42

I don't think so. The error per cent will typically be the same across the entire range. A good meter will have a calibration chart. Or you can make one.

But 5% is not a very good meter.

I think you're going to lose that bet!

Dear Prajith,

I think there should not be change in % error limit. It should be less than 5%.

Dear Prajith,

Hope your question is answered clearly by Mr. hilton and cjanand.

please post your comments

5% + or -....? get a new meter....Your accuracy should be + or - >1%....

5% is >1%. Should be <1%.

From the CR4 FAQ.

• Do your own homework. CR4 is not a homework cheat site. While some here might relish the opportunity to sharpen up old rusty skills by working the homework problem, consider the following and consider it well. If you cheat on your homework by using someone else's answers, you are only cheating yourself, because the purpose of any homework or other academic assignments is to help you learn - by practice, repetition, and self-discovery.

Now if you show us the work you did for this problem and required further help, had an insight you wanted confirmed or explained, or basically somehow showed us some competence then I and many others will help you her.

I don't know about you guys, but a VOM with +/- 5% would go in my kids' toybox.

...or would be recycled under the terms of the WEEE Directive here.

I would attempt to calibrate it. I have several large hammers perfect for the task.

Every meter I ever bought from Radio Shack is certainly there.

Accuracy is 5% whether you are reading mid-scale or full scale. Is this an analogue or digital meter? Poor quality in any case...replace at first opportunity.

OFF TOPIC ?????

Measuring instrument error value is always indicated as percentage of the full scale, for readings from the minimum to the maximum. So the error in this case is 5% of 100 (FSR). This is the worst error that can arise between "minimum scale" (guessing it is 0) to 100V. So the true value could be anywhere between 45 to 55 V.

Measuring instrument error value is always indicated as percentage of the full scale

No. It could be % of reading.

Dear Prajith,

Hope your question is answered clearly by Mr. hilton, Ormonto and cjanand.

please post your comments

2.5 %. Assuming your meter is zero'd AT Zero, and off by 5% at 100, half way up would be 2.5 volts wrong. How likely is it to be otherwise guys?

Very likely to the point of near certainty. Particularly since you started with an assumption.

I always zeroed MY voltmeters at zero. I make no real assumption about what the O.P. would do. I hold out little hope actually, but perhaps I am biased against students who should know better. (Especially the old mechanical VOM's. come to think of it, I don't ever remember zeroing my digital ones at all, just cross the leads and make sure they go to zero. There may be a pot inside to set it to zero, but damned if I ever opened a VOM to find it!)

And as an aside, what an unusual question the O.P. came up with. One is reminded of other places where you work with verifiable pre-existing errors...like standard deviation in compass readings and tension-compression caused vertical radian angle deviation in response to wind loading on radar masts. Has its place, but I have not dealt with any of these problems for a very VERY long time!

Compass swings are still done, (even in these days of GPS) but I can't remember ever having to deal with a compensation to a radar or microwave mast, like, ever. Ever deal with such problems Red? (I don't mean sag from weight or age but less predictable loading)

I regularly have to reeducate very bright people about measurement uncertainty. [Uncertainty is a better description and does not imply an emotion that "error" does.] I myself have not dealt with uncertainty with GPS.

Turn right NOW!

Recalculating.... Recalculating...

Uncertainty with GPS has now become a standard joke used in many car insurance commercials.

2.5 volts out of 50 is still 5% off, not 2.5%. Moreover, error ratings are normally based on full scale, thus becoming larger percentages at partial scale.

Interesting. And not just semantics. Now you are inspiring me do some experiments. GA. Maybe the professor's question was a real "gotcha" test question!

Oh, am I wrong? I can't see how. But I am willing to be educated. I have been wrong before...grin!

Yusef,

You are assuming a linear error across the full scale, which is not the case.

The error can arise anywhere along the scale.

To calculate the percentage error while measuring 50 V has to use some points and better to use this like the actual value(A), the forecast (F) as the denominator, take some other apart from (A) and (F), the formula for this is:-

" %error=|Difference of the two values|/Average of two values *100"

Almost all spec's for VTVM's is PLUS or MINUS some per cent of full scale. That would mean your meter is +/- five volts if you are on the 100V scale. For better accuracy, set it on the 50 V scale.

Also, nearly all inexpensive VTVM's are accurate for sine waves only. If your waveform is distorted, there will be even more error.

A VTVM? Now that's real old school technology.

That sounds like what he has!

You lazy man work it out yourself!!!