I wonder if a hand-held anemometer would have significant back pressure?
It's fairly easy to convert flow rate to volume if the duct size is known.
Inexpensive units go for 20-30 USD on eBay.
The "Bagometer" method is straightforward as well; just curious about
alternatives.
73,
Jim N7CXI
On 4/13/2011 11:04 AM, Ian White GM3SEK wrote:
> John G3UUT 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.
>>
>
> I'm not sure if a peak flow meter will work, because of the
> back-pressure through the device itself. The bag method may look crude,
> but it has the advantage of a very low back pressure.
>
> To save you from getting cold and wet, a British swing bin bag is about
> 50 litres. (This is probably a Euro standard size, and also a good shape
> for attaching to the outlet vent.)
>
> With care, cardboard and packing tape, you can make volume flow
> measurements within about 10%, which is plenty good enough.
>
>
> 73 from Ian GM3SEK
> http://www.ifwtech.co.uk/g3sek
>
>
>> 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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