The photo shows the relevant portion of the Inguard circuit.
It appears to me that if I disconnect and short the voltmeter inputs at J9 & J11 and remove E1 I should have the relay boards feeding the back panel banana jacks which I can connect to my 3457A.
Does jumper J3 set to no A/D allow directing the 100 inputs from the 3497A to an external meter?
Goal is to select a channel with the 3497A and measure with a 3457A. If that goes well I may well spring for a 3458A.
I have a 3457A which will give 7.5 digits. I have in mind measuring 80 or so voltage references over a multiyear period along with temperature control and logging.
This is motivated by volt and time nuts posting plots accompanied by unsupported claims, but refusing to provide the digits for independent analysis . All I've asked for is a chance to be proven wrong without having to wait for years to record my own data. After 10 years of asking I'm going to collect my own data. Simply put, I am a reflection seismologist. We invented DSP in the 1950s (search for " MIT Geophysical analysis Group under Norbert Weiner" for proof).
Reg
