Products > Test Equipment
Keysight 34461A Fan Noise
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nctnico:
A quick off-the-cuff calculation makes me think that the differences measured with the different fans are well within the 34461A's specification. The 34461A's spec also shows a few PPM of drift per degree Celsius of temperature change. So using a fan with more or less airflow is going to affect the 34461A's readings a little bit as well because the internal temperature will be different.
Messtechniker:
See graphs of the 34465A internal temperature measurements
using the stock fan and the Noctua replacement fan.
Please note the different logging periods.

Measurement conditions:
1.) 34465A off over night.
2.) 34465A switched on early in the morning.
3.) After starting up, started logging immediately and left the lab.
4.) Did not enter the lab while logging.

Conclusion: not much to be seen here as to the different fans influencing the internal temperature. I'll leave the stock fan installed since there is not much to be gained by replacing it with the Noctua fan.
Cutting noise levels down to signifiant levels will here require a redesign of the air flow outlet, preferably with the assistance of an air flow expert (from the car or aircraft industry). Anyway some insights were gained.


Messtechniker:
Here now the logs
radhaz:
You could always get one of these, it has no fan.
https://www.eevblog.com/forum/testgear/iwatsu-voac-7602/
rernexy:
Yesterday my 34461a started producing an extra sound, like a pulsing at high frequency. That sound can be heard in the first attached mp3 (isolated it using a high pass filter on the original audio).

Has anyone ever heard that in their 34461a, or in a related Agilent/Keysight bench DMM?

The sound it usually made is just the high pitched whine from the fan. That can be heard in the 2nd mp3 (isolated it using a low pass filter on the original audio).

The 3rd mp3 is the original unfiltered audio of the noise my 34461a now makes.
The jpg is a spectrogram of the audio, starting from powerup.
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