In article , Arfa Daily
wrote:
Ok, so who knows a bit about measuring audio power ? Setting aside any
furious arguments about peak power, rms power, average power,
backpeddling average peak music power on any given friday in March etc,
does an audio power meter sum the power in both half cycles to arrive
at a reading, or just one.

I suspect this depends on the actual 'power meter' in question. :-) May
have a precision rectifier and take an average from that , or may use
something else. e.g. the old avos tend to give a decent result if
calibrated, you know the load, and are using a sinewave.

I guess what I'm asking is half wave reccy ahead of the meter, or full
wave bridge ?

If it uses a rectifier then takes a time-average I'd expect a good one
to use a full wave precision rectifier - i.e. one that suppresses the
forward voltage drops in the diodes. Cheap enough to do at audio
frequencies.

These days a meter might simply sample rapidly and work out the rms
voltage and report that. Years ago, it might have used an analog
multiplier to obtain the square-law for audio. I guess people like
Burr-Brown still make these. (?) As Don has pointed out, a thermal
meter might be used in some applications. These (and single diodes)
still get used for RF power measurements.

However unless you are using a sinewave, the reported value may be
misleading. Ditto if the load isn't resistive.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article , Don Pearce
wrote:


The type of rectifier doesn't make a great deal of difference, although
full wave probably has the edge on accuracy. Don't put a capacitor after
it, just let the meter do the averaging, then do the sums: power = v
squared / R.

I'd be wary of this unless I knew the details of the meter. I've seen some
that can give odd results when asked to give a dc level in the presence of
much ac. e.g. One I recall seemed to only sample the input at a low rate,
so became confused as the level flutuations 'beat' with its sampling rate.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article , Arfa Daily
writes
Ok, so who knows a bit about measuring audio power ? Setting aside any
furious arguments about peak power, rms power, average power, backpeddling
average peak music power on any given friday in March etc, does an audio
power meter sum the power in both half cycles to arrive at a reading, or
just one.

I guess what I'm asking is half wave reccy ahead of the meter, or full wave
bridge ?

Arfa



Is this the arfa daily who's a service tech?..


FWIW if its just the output of an audio amp I just use two bloody great
8 ohm resistors on a large heatsink with stout cables to reduce ohmic
losses, and connect that to the amp and use me trusty Fluke bench DMM to
measure the AC power developed when running a sine wave with the Hewlett
Packard distortion analyser keeping note of the distortion level to see
when its going into clip.

Measure that at a few different frequencies and square the AC measured
volts and divide by the 8 'ommes and thats the RMS power.

Sufficient and accurate and IMHO a good indication of what the amp will
develop.....
--
Tony Sayer

"Phil Allison" wrote in message
...

"Keith Gutless Wonder "



** Not up to having a technical debate - are you Keith ?

So you post BRAIN DEAD insults while hiding your identity.

How pathetic.


Typical, useless pommy waste of space and usenet cretin.




Like I've got the time and/or inclination to play *hard case* typing games
with you, little boy....

"Keith Gutless Wonder "



** Not up to having a technical debate - ARE you Keith ?

So you post BRAIN DEAD insults while hiding your identity.

How PATHETIC.


Typical, useless pommy waste of space and usenet cretin.






....... Phil

"Peter Weis"


** What a pathetic pommy, audiophool jerk off.

The whole UK is crawling with them......







........ Phil

"Phil Allison" wrote in message
...

"Keith Gutless Wonder "



** Not up to having a technical debate - ARE you Keith ?

So you post BRAIN DEAD insults while hiding your identity.

How PATHETIC.


Typical, useless pommy waste of space and usenet cretin.



Hey, dope - did you miss this bit:

"Like I've got the time and/or inclination to play *hard case* typing games
with you, little boy...."

???

"Keith Gutless Wonder "


** Not up to having a technical debate with ANYONE

- ARE you Keith ?

So you continue to pots BRAIN DEAD insults while hiding your identity.

How bloody PATHETIC !!!


Typical, of countless, useless pommy wastes of space and usenet cretins.







....... Phil

"Phil Allison" wrote in message
...

"Keith Gutless Wonder "


** Not up to having a technical debate with ANYONE

- ARE you Keith ?

So you continue to pots BRAIN DEAD insults while hiding your identity.

How bloody PATHETIC !!!


Typical, of countless, useless pommy wastes of space and usenet cretins.



The temptation to jerk you around for a couple more hours ('til I go out)
just to deprive you of sleep and give you a raggedy-arsed start to the week
is strong (what is it now in Horse Trailier - 2:00 am?), but I simply cannot
deal with the *boredom/crassness* of it all...

(Take yourself off to bed with a nice hot mug of Milo - the world'll seem a
better place tomorrow! ;-)

"tony sayer" wrote in message
...
In article , Arfa Daily
writes
Ok, so who knows a bit about measuring audio power ? Setting aside any
furious arguments about peak power, rms power, average power, backpeddling
average peak music power on any given friday in March etc, does an audio
power meter sum the power in both half cycles to arrive at a reading, or
just one.

I guess what I'm asking is half wave reccy ahead of the meter, or full
wave
bridge ?

Arfa



Is this the arfa daily who's a service tech?..


FWIW if its just the output of an audio amp I just use two bloody great
8 ohm resistors on a large heatsink with stout cables to reduce ohmic
losses, and connect that to the amp and use me trusty Fluke bench DMM to
measure the AC power developed when running a sine wave with the Hewlett
Packard distortion analyser keeping note of the distortion level to see
when its going into clip.

Measure that at a few different frequencies and square the AC measured
volts and divide by the 8 'ommes and thats the RMS power.

Sufficient and accurate and IMHO a good indication of what the amp will
develop.....
--
Tony Sayer

Hi Tony

That's me. Useful input. Thanks.

Arfa