The peak flow meters I found in a casual web search all go up to 800
liters/minute. Assuming I'm converting units correctly, that only works
out to roughly 28 cubic feet/minute.
Just as an example, the old Eimac data sheet for the 8877 says it
requires 38 cubic feet/minute at sea level for continuous operation at
1500 watts anode dissipation.
I agree it's a great idea, but again assuming I haven't miscalculated
here it doesn't look like they measure quite enough at the high side to
use with legal-limit amplifiers.
Anyone find a "larger" one? This is worth some investigation.
73,
Jim N7CXI
On 4/13/2011 9:34 AM, Shane Youhouse wrote:
> I never thought of using one of those, but great idea. I've got two, my
> son has asthma and one of them was questionable... Guess I found a use
> for it :)
>
>
> You can usually source them locally for 10-30 dollars... Call a medical
> supply store.
>
> Even some of the better stocked pharmacies have them.
>
> --Shane
> KD6VXI
>
>
> On Wed, 13 Apr 2011 09:24:05 -0700, John G3UUT<amps@grebe.plus.com> wrote:
>
>> Well that's a relief! I was planning on spending the weekend messing
>> around with bin liners and water butts. It looks like these things are
>> available real cheap on Ebay.
>>
>> 73 John G3UUT
>>
>> On 13/04/2011 12 :25, Angel Vilaseca wrote:
>>> An accurate way to measure airflow is to use a peak airflow meter. See
>>> picture here:
>>>
>>> http://en.wikipedia.org/wiki/File:Peak_flow_meter_vert.jpg
>>>
>>> This is a low-cost device used by persons with asthma to self-monitor
>>> their disease. Widely available worldwide.
>>>
>>> 73 de
>>>
>>> Angel Vilaseca HB9SLV
>>>
>>> Ian White GM3SEK a écrit :
>>>> Roger (sub1) wrote:
>>>>
>>>>
>>>>> One other point, I've seen the question raised about how much pressure
>>>>> was a fan generating. For a given tube and existing system you can
>>>>> treat air flow and pressure the same as voltage and current. IF you
>>>>> are
>>>>> getting the required air flow you MUST have the required air pressure.
>>>>> Insufficient pressure and you will have insufficient flow. Get the
>>>>> proper flow and you will have the proper pressure.
>>>>>
>>>>> IF the radiator is plugged or partially clogged you will have high
>>>>> pressure and low flow. But again, it the flow if proper then so is the
>>>>> pressure.
>>>>>
>>>>>
>>>> Air flow rate is what really matters in cooling, and all data sheets
>>>> for
>>>> air-cooled tubes will state the minimum volume flow rate required.
>>>> Pressure drop is only an indirect way of measuring the volume flow
>>>> rate... and actually a very poor way.
>>>>
>>>> Pressure drop measurements in real amplifiers are very prone to errors,
>>>> because the reading will depend critically on the orientation of the
>>>> manometer pickup tubes relative to the air flow. We have no idea what
>>>> the tube manufacturers did to minimize those errors... or even if they
>>>> were aware of them. Because of all these problems, pressure drop is
>>>> probably the wrong thing for us amateurs to measure.
>>>>
>>>> It's actually MUCH easier to measure the volume flow rate directly. No
>>>> elaborate equipment is needed - simply time how long it takes for the
>>>> outlet air to fully inflate a large, lightweight plastic bag. With a
>>>> little care you can measure the volume flow rate within about 10%,
>>>> which
>>>> is far more accurate than a pressure measurement.
>>>>
>>>> The original idea came from George Daughters K6GT, and details are
>>>> right
>>>> here in the AMPS archives:
>>>> <http://lists.contesting.com/archives//html/Amps/1998-03/msg00172.html>
>>>>
>>>>
>>>>
>>>>
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