Valhalla 2720GS

[maxwell3e10]

Well, this makes it easy: 25 60 02 12 58

[Kleinstein]

A capacitance measurement should tell which shield is close to which winding: e.g. the shield to PE should have the largest capacitance to the primaries.

[branadic]

The primary winding is the inner one, so you can tell which of the screens is the inner one too (the closest to the core), which has to be connected to earth. The other two screens are physically tied together on the mainboard, so it doesn't make a difference to which solder point you are connecting them.

-branadic-

[branadic]

Here are results of my Valhalla2720GS-HSR-ADR1399 running for almost 2200 h.
One might be suprised by the bad behavior, but that can be explained. The measurements suffered from EMI of what I called a scream cube (a 1 m³ fine particle filter that was running near one of our test benches) nearby. This scream cube was switched off 11 days ago and we can see how temperature in the lab stabilized and output noise went down to a reasonable level since then. We can also see some jumps that resulted after performing internal cals of the Valhalla.
Since the scream cube will not be turned on again, the related project has ended, I guess it makes sense to repeat the noise measurements, but also to further observe how stability turns out from here.

-branadic-

[branadic]

An update of my Valhalla 2720GS/HSR-ADR1399. I'm approaching 5000 h of operation after my repair, modifications and upgrade. Since removing the "scream cube" from the lab the extreme spikes disappeared and never showed up again by now.
At some point I had to readjust the oven settings of my copycat reference board 4, as the reference board was continiously turned off by the unit due to an "oven high" failure. The components and thus the voltages had drifted quite a bit. Since I made the adjustment the board was never turned off again.
What I observe are some large intermittent deviations, which I think are due to the units internal intercomparison of the references, as they appear at least at around 12:00 pm. I can tell, as ACAL of 3458A happens every day at 8:00 am, hence the gap in the data.
The location of the equipment near the AC in the middle of the room is far from ideal and the south side of the lab with its mirrored glass window front isn't perfect either, but it is how it is. There is clearly some temperature depence that needs to be ruled out.

I also received data of an INL measurement of another 2720GS against a Datron 1271 from some fellow voltnut that I attach. Again, results are disappointing given the claims Valhalla made: "The 2720GS delivers the performance required to calibrate the world's most accurate 7.5 and 8.5 digit DVM's yet does even more."

-branadic-