[time-nuts] HP5370 power supply measurements
alexpcs at ieee.org
Fri Jul 15 18:35:52 EDT 2016
PABST KG in the Black Forest (Germany) made very quite high efficient
fans, HP used to use these fans for awhile, but the company was sold and
the quite fans disappeared, the new fans from the new owner
http://www.ebmpapst.us/en/ are cheaper but not so good
On 7/15/2016 1:25 PM, Tommy Phone wrote:
> Some thirty years ago fans for automotive radiator cooling were designed with 7 unevenly spaced blades to reduce the siren effect yet yield comparable air flow. Careful layout and blade sweep back along with an annular ring made it entirely feasible to have a statically and dynamically balanced fan as it came out of the mold. I always wondered why the folks who make these little fans can't figure out how to do that. Maybe getting comparable CFM from a much smaller fan violates some Reynolds number requirement for turbulence control.
> From Tom Holmes, N8ZM
>> On Jul 15, 2016, at 3:52 PM, William H. Fite <omniryx at gmail.com> wrote:
>> That is, in fact, precisely how you do it.
>>> On Friday, July 15, 2016, Orin Eman <orin.eman at gmail.com> wrote:
>>> On Fri, Jul 15, 2016 at 10:55 AM, Poul-Henning Kamp <phk at phk.freebsd.dk
>>>> In message <
>>>> CANy2iXq6ONvriDoFgNFkEBQjDKntP7t8KuE7BOUpxJWLCuxLsw at mail.gmail.com
>>>> , "William H. Fite" writes:
>>>>> David Kirkby scripsit:
>>>>>> I often here of people replacing fans with quiter ones, but I suspect
>>>>>> all they really do is reduce the airflow.
>>>>> Not necessarily, Dave. The Austrian company, Noctua, for one, makes
>>>>> extremely quiet fans with excellent airflow.
>>>> ... at zero pressure differential, which is easy to do (Think: ceiling
>>> You have to look at the curves on the data sheet that shows air flow vs.
>>> static pressure (and be careful about the static pressure scale). I found
>>> that a 'quiet' fan would often be flowing one tenth as much air as the
>>> original fan at the static pressure at which the original fan was rated.
>>> In a given instrument, you may get away with the quieter fan, but how would
>>> you tell other than putting a thermometer inside and making a before/after
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