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Re: [Amps] Bag-o-meter calcs in US units

To: Jeff Blaine <keepwalking188@yahoo.com>
Subject: Re: [Amps] Bag-o-meter calcs in US units
From: Jim Barber <audioguy@q.com>
Reply-to: audioguy@q.com
Date: Wed, 13 Apr 2011 15:55:27 -0700
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Not my idea, just trying it on for size.
Ian mentioned who thought it up originally, but I've forgotten already. 
What were we talking about? ;-)

73,
Jim N7CXI

On 4/13/2011 3:16 PM, Jeff Blaine wrote:
> Now THAT is out of the bag thinking!  Brilliant.
>
> 73, Jeff ACØC
> www.ac0c.com
>
> -----Original Message-----
> From: Jim Barber
> Sent: Wednesday, April 13, 2011 3:14 PM
> To: AMPS
> Subject: [Amps] Bag-o-meter calcs in US units
>
> Not to run it into the ground, but does this look right?
> (in US units)
>
> . Construct a duct of heavy paper to match/mate the air output duct on
> the amplifier, tape it to a US-standard 33-gallon trash bag
>
> . Flatten the bag to eliminate as much trapped air as possible
>
> . Fire up the amp and allow the blower to come up to speed
>
> . Stuff the paper duct onto the amplifier output duct (get as good a
> seal as possible) and simultaneously start the watch
>
> . Stop the watch at the point where the bag is fully inflated
>
> So assuming it took roughly 2.5 seconds to inflate the 33-gallon bag:
>
> (1) 33 gallons * 0.13368 = 4.414 cubic feet
>
> (2) 2.5 seconds / 60 = .0417 minutes
>
> (3) 4.414 / .0417  = (is roughly equal to) 106 cubic feet per minute (CFM)
>
> Seems like the very short inflation time would reduce the practical
> accuracy of the measurement for larger amplifiers, but you could
> certainly get a rough number. Very useful.
>
> 73,
> Jim N7CXI
>
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