Yeah, error is a real issue.  If you really want good results you're going to
have to spend a couple tthousand dollars on a good meter.  A couple hundred will
get you something that will be acceptable but those $20 rat shack meters don't
even calibrate correctly.  They only get you sort of in the ball park.

Actually, you can use an old tape recorder or cassette recorder's vu meter to
get you in the ball park.  Problem with single shot spl readouts is that you
have to have very slow waiting for them to mean anything and they're only a
snapshot of time.  I've used a variable tone circuit attached to the output of a
meter with serial output of diaplay.  You almost have to be in another room with
this but with wireless connectivity its not that big a deal these days.  That
way you can do scanes a-d as well as spl and any specialty scales that you need
for your application.

For the record, those rat shack meters are generally C scales rather than true
spl which doesn't matter much to most people but they actually are different.

Tom


Tom Brennan  KD5VIJ, CCC-A/SLP
web page http://titan.sfasu.edu/~g_brennantg/sonicpage.html