I have the DMM-Check (8 months old), Penta-Ref (4 months), and a Geller SVR (2 months).
A month ago I had tested all three references and they appeared to be very accurate. I received a new, calibrated, Agilent 34410A DMM and decided to retest the references. The SVR and the DMM-Check both appeared to have remained accurate, but the Penta-Ref was a different story.
The Penta-Ref had been quite accurate in February, when I checked it with a borrowed calibrated Agilent meter. But, on 3/20 with a new 34410A it seemed off. The next day I thought about it and checked the two 9-volt batteries which power the Penta-ref… sure enough, they were running a bit low. With the Penta-ref switched on, the battery voltages were 8.92 and 8.97. I replaced them with brand new batteries (9.6volts) and re-ran the tests. That fixed it, the Penta-ref was back on track.
On a similar note, the Geller SVR provided a steady 10.0000 volts output using an input voltage as low as 10.945V.
Geller SVR 23.5° CValue 34410A Fluke 28910 Volts 10.0000 10.000
Penta-Ref New batteries 22° C Old batteries 23.5° CPenta-ref 34410A Fluke 289 34410A Fluke 2890.2500 0.25013 0.25013 0.25426 0.24543
0.4900 0.49007 0.49009 0.49821 0.4983
0.5100 0.51009 .51012 0.51855 0.5186
4.9000 4.9001 4.9004 4.9817 4.982
10.0000 10.0000 10.0001 10.1666 10.167
DMM-Check 23.5° CValue 34410A Fluke 2895 Volts 5.0002 5.0006
1 mA 0.99994 1.003
999.4? 999.23k 999.3k
9.996k? 9.9961k 9.999k
99.97k? 99.976k 99.99k
A few days ago I was contacted by Doug Malone of VoltageStandard.com,
he noticed my post and felt that the Penta-Ref should not experience a problem with the battery levels that I listed. He requested that I return it for adjustment/repair. So, I’ve sent it, and the DMM-Check to Doug for calibration. I’ll post new results when I get the units back from Doug.
That’s great customer service!
Also, it looks like there’s a new model coming, the DMM-Check Plus. It will include a 5VAC rms voltage reference, 1mA rms AC current reference, 100Hz precision frequency source, and 0.1%, 10ppm 100OHM precision resistor
Note that on the Geller SVR, he will ask you what temperature to use for the calibration. So, that might help with your warm lab.