I have also reorganized my bench as I wrote some weeks ago (photos still to be made, not ready yet).
One positive effect is being able to pull out single instruments out the rack.
I used that for swapping the quartz in my HP 3456As that determine the integration time of the A/D conversion from the 60Hz-type to the 50Hz-type.
I ordered some custom made quartz built to HP specs some years ago and had them waiting for use since then -because swapping them in would have meant to tear down all the stack my HP 3456A were sitting in.
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/facepalm.gif)
Since the change in noise level with the right quartz (50Hz type) was noticeable I decided to do some statistics using the built in the 3456A statistics functions.
(I also tested my shorting plugs with this.)
I checked my two working units #1 and #2, each with 50Hz-synchronous integration time and once with 60Hz-synchronous integration time.
Auto-zero was ON and filter was OFF.
Here's the raw data:
| #1 / 50Hz | #1 / 60Hz | #2 / 50Hz | #2 / 60Hz |
upper | -00.0000E⁻3V | +5.40000E-6V | +1100.000E-9V | +6.00000E-6V |
lower | -4.00000E-6V | -7.40000E-6V | -2.40000E-6V | -6.00000E-6V |
mean | -1586.778E-9V | -1634.096E-9V | -521.938E-9V | -602.368E-9V |
variance | 0.000049E-9V | 0.004099E-9V | 0.000036E-9V | 0.002787E-9V |
count | 141.8320E3 | 147.3180E3 | 124.5800E3 | 157.3460E3 |
It's clearly visible that the "right" quartz for the A/D integration time being synchronous to the mains power (50Hz in my place: Germany) has a significant effect; it's roughly a factor 100 looking at the variance.
![Shocked :o](https://www.eevblog.com/forum/Smileys/default/shocked.gif)
I'm quite pleased about these results.
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/smiley.gif)
I started the same test with my 3457A and it seems to be worse by roughly a decade (~147E-9V);
It's significantly noisier -but that's no surprise when taking it's front end construction into account..
![Popcorn :popcorn:](https://www.eevblog.com/forum/Smileys/default/EatingPopcorn.jpg)
Conclusion: Do work with the HP 3456A only with the right integration time, use the right quartz for synchronizing the A/D-conversion integration time to the frequency of your mains power systems in your place. Otherwise you loose roughly two digits resolution to (unnecessary) noise.
Edit: Added conclusion