Hi all, I have a nice DVM that has recording and PC interface and I would like to use it for a sound pressure level meter. I would not mind buying something that does this, but all I can find are complete units. Anysuggestion on how I can do this myself without getting into "yet another project"?
thanks chuk
** I gather you want to measure and log SPL readings over some period of time - right ?
A great deal depends on what range of SPLs you need to be able to read and over what frequency range.
DMMs are not sensitive to the tiny signals levels that typical mics deliver or to the highest frequencies in the audio band.
More info on what you REALLY require will permit others to give good advice on cheap and simple solutions.
........ Phil
I am confused, what more do you need?
I want to measure Sound Level. RS makes a meter that I can buy for $50. I already own a nice DVM. So why spend the $50? Is there anyway I can turn a DVM into a SPL Meter?
** Go buy the damn RS one.
Since you are not interested in " yet another project ".
....... Phil
No.
Graham
Hmmm, we'll I guess this is no effin good. What did you guys even get out of grade 8 electronics? Stupid Americans
Sure, just add a calibrated mic, mic preamp, A, B, and C weighting curve filters, a precision rectifier or true RMS circuit, a smoothing filter with adjustable time constants, and a log converter and
*presto*, an SPL meter!Best regards,
Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis
Chuck, you actually got a good set of responses from Phil, Graham and Bob (and I don't believe they're all from the US, either). It might have been a little brusque, but these guys are all very capable. The way you describe your requirement (i.e. not another project), it can't be done. Mr. Masta described exactly what you'd need to include in your project.
Possibly if you learn a little more about SPL measurements, you'll understand why it's more complicated than just cobbling together an op amp or two:
The Radio Shack Sound Level Meter (Catalog #: 33-2055, $49.99) is actually a pretty good deal for what you get. If you don't need automatic datalogging, I'd suggest you go that route. And if you do finally decide to cobble something like Mr. Masta's suggestion together, you could do worse than borrowing an RS meter to calibrate your project. Output readings on the one I got for a factory job several years ago compared pretty favorably above 75dB (A weighting) with an instrument costing about twenty times that much.
If you do need datalogging, I guess you might want to rent or borrow one of those SPL meters costing twenty times more which have a DC voltage output proportional to reading, and just log that with your RS datalogging DMM.
Cheers Chris
But then won't you end up with a bulkier package than the storebought sound level meter?
And then won't it cost a fair percentage of the storebought sound level meter to get the parts for building it, especially for someone who doesn't have much of a background in electronics?
The problem with people who "know something can't be difficult" is that they often don't know what's involved, so they think it should be really easy to turn a DMM into a sound level meter.
Michael
Ahh, my comments were all with tongue firmly planted in cheek! I assumed he didn't know how difficult it was, and was trying to show that it was not at all simple.
To the OP: If your goal is to own a nice portable SPL meter, the RS unit is a good deal, whether you get the digital model or the older analog one (if it's still offered).
If you just need SPL measurements, my Daqarta package allows you to calibrate your sound card to do that. However, as you might imagine, you have to have a calibrated mic. Just getting one of these will cost more than the RS meter.
So far, I've never found any good way to calibrate a mic other than by comparing to a known reference mic, or using a reference sound source. (There are some theoretical-but-impractical methods that work with certain kinds of mics, that don't require a reference.)
Best regards,
Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis
Your comment is uncalled for, and innacurate. Neither Phil nor Graham are Americans, and neither are stupid.
Ed
Sure. Get a calibrated mic, and measure its output voltage. You might want an amp of some kind, if it's a low-output mic (which the really classy ones usually are.)
Then again, you might find that a decent mic costs more than the sound level meter - talk to the RS guy, and see if replacement parts are available - it's just a mic and a vu meter. - oh, yeah; vu meters have a log response.
Given that, you might want to use your PC interface and some S/W to give you the log response, and calibrate the gain to read out directly in vu or something.
Have Fun! Rich
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.