Hi all,
Decided to take some readings from my 3458A's and see where they were, primarily interested in No.2. I have been playing around with some hardware & software to stabilize the workshop temperature 24/7 and can now play with the 3458A's knowing the ambient is stable. At the moment i've recorded 0.5degC change in past 36hrs and will tweak the setpoints to get it better.
No.1 (Feb 2000) = my original unit
No.2 (Jul 2009) = Repaired unit, new A3 board.
No.2 seems to be running a bit warm (factory flat type filter with spacer plate etc installed) compared to No.1 (original cup type filter), so I ran some tests with various materials to see how they compare including removing the metal spacer as it looks like it could restrict airflow.
The best I came up with (apart from no filter!) is a piece of stainless steel filter mesh cut to size and fitted without the plate but with the guard. This brought the temp down to just 1 degC above No.1.
Here's my tests of No.1 & No.2 before abandoning No.2 test to fix the filter issue.
No.1:CAL? 72
36.4 to 36.7 degC
1-day Drift PPM = 0.0132
.....7-day test on-going.
No.2:CAL? 72
40.4 to 41.2 degC
1-day Drift PPM = -0.3564
.....abandoned test
PS. Thanks to TiN for the spreadsheet idea (xdevs site), I've now made my own......
Filter removed and choosing mesh size:
App running controlling air-con unit and heater. Based on USB-TnH SHT10 temp probe.
Ian.