From: Robert Baer
X-Mailer: Mozilla 4.75 [en] (Win98; U)
Subject: Re: wattage meter exists??
Date: Sun, 08 Sep 2002 06:40:35 GMT
NNTP-Posting-Date: Sat, 07 Sep 2002 23:40:35 PDT
Organization: EarthLink Inc. -- http://www.EarthLink.net
John Woodgate wrote:
> I read in sci.electronics.design that Robert Baer
> wrote (in <3D79ACA8.CE5E286@earthlink.net>)
> about 'wattage meter exists??', on Sat, 7 Sep 2002:
> >John Woodgate wrote:
> >> I read in sci.electronics.design that Bob Wilson >> pam.bc.ca> wrote (in ) about 'wattage
> >> meter exists??', on Fri, 6 Sep 2002:
> >> >In article <email@example.com>,
> >> >firstname.lastname@example.org says...
> >> >>
> >> >>Hi! Is there any device such a wattage meter that exist?
> >> >>How much and where?
> >> >>Thanks
> >> >
> >> >
> >> >Of course there is! I have a nice one that reads accurately both real power
> >> >(wattage) and apparent power, from nearly DC to well above 100HKz. More
> >> >standard ones that work at line frequency have been around for almost
> >> >centuries!
> >> >
> >> Yes, but will it measure the 'wattage' of the sound from a 650 W PMPO
> >> computer sound system? (;-) We don't quite know what the OP has in mind.
> > Well, if all one wants is an estimate of power out of a sound system
> >(and that is all that is done to get those "specifications" and
> >sometimes less), then use a resistive load of the proper impedance (eg:
> >8 ohms, 16 ohms, whatever the speakers or headphones are supposed ot be)
> >and measure the voltage across each resistor at the specified inoput
> >drive level; usually 1Khz is used, but 440Hz is OK also, as power levels
> >are almost never guaranteed over a specified frequency range.
> > Usually a frequency response is given with no directly stated link to
> >the power level specified, and power level is just that - with no
> >frequency involved at all.
> Yes, I am sort of rather familiar with all that, but notice that I wrote
> '...'wattage' of the *sound*...'. A sound power meter is very different
> form an electric power meter.
> > There is a lot of stupidity and false implications involved with most
> >"specifications" of audio amplifiers made to drive speakers and/or
> > There have been some exceptions to this generality, but the makers of
> >that equipment had a lot of integrity and really cared about their
> >products and customers.
> > Virtually all audio stuff made for computers is cheap crap, some that
> >seems to work well, but junk nonetheless.
> Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
> Interested in professional sound reinforcement and distribution? Then go to
> PLEASE do NOT copy news posts to me by E-MAIL!
Sorry, read incorrectly.
SPL or Sound Pressure Level is measured with a calibrated capacitive
microphone, usually under rather tightly controlled conditions
(temperature, humidity, air pressure, acustic enclosure at minimum).
I think GR made some of those, and there should be others. Original
cost was rather steep, and it may be hard to find used ones on the
surplus market; expect to pay a lot for one.