Quiet Noctua Fans for Keithley 2002 and 2001 - Not advised.

[pamphonica]

I have contemplated for a while quieting my Keithley 2001 and 2002 by using Noctua fans, which are often recommended for their low noise and good performance.  A re-cap of both DMMs re-opened the fan debate.

I checked the specs for the existing Elina fans and the Noctua NF-A4x10 fan I have used elesewhere.  The worrying thing was the airflow, at only 65% of the original.  The Noctua is a slim 10mm fan and the Elina is a 12mm fan.  There is absolutely no room for a thicker fan as the pcb pretty much butts against the fan

Test time.  I rigged up a minute RTD PT100 sensor on fine wires inside my K2001 and let it run for 15 hours, first with the original fan, then the Noctua fan.
The results were conclusive.  The existing (rather noisy) fan keep the interior at about 38 degC.  The incredibly quiet Noctua only manages to keep it at 48 degC.
That's not a good result so I won't be using the Noctua fans as replacements. It's not worth trying the test with the K2002 - I'll just put up with the fan noise.

Interestingly, the K2002 has a different airflow internally, compared to the K2001.  It uses the same plastic cover over the analogue board but the K2002 adds a clear plastic guide to put all the air through a hole into the inside of the cover.  The K2001 has no guide and no hole in the cover so all the air goes round the outside.  Presumably in the K2002 it is more important to keep the 8.5 digit analogue electronics happy than the power supply regulators etc!

-Jeremy

[SeanB]

Noisy fan often will be quiet again with some surgery to add oil to the bearing in the fan. Easy to do with a peel of the label, and a  insulin syringe to add 0.2ml of 5W synthetic oil into the bushing cavity, then put the cap back.

[J-R]

Try a single 20mm fan outside the chassis or two fans in series, one inside, one outside: https://noctua.at/en/axial-fans-in-series-or-parallel-operation