[volt-nuts] Wavetek 1281 - Selfcal Module
tmicallef at gmail.com
Sat Oct 31 11:13:51 EDT 2015
No problem. I was just looking back at the documents wondering if I missed
anything. The transformer solution is interesting and I see that the 8508A
has a second low voltage transformer (T1). I have no idea if it performs
the same function using a different calibration.
On Sat, Oct 31, 2015 at 9:33 AM, Frank Stellmach <frank.stellmach at freenet.de
> you already have sent me the appropriate SelfCAL circuitry, but I did not
> recognize (understand) it as such!
> I also received a hint from another volt-nuts, John, about the complete
> documents for the DATRON 1271 on the KO4BB site, which is very similar, and
> also contains a SelfCAL module, being a bit different than the one inside
> the 1281.
> The schematics for the 1271, anhow reveal how the transformer inside this
> module provides different voltage ratios. The transformer there is labelled
> +9.93V, +/-7.23V (that's the main references value), 1.83V, 1.00V and 0.19V.
> These ratios were generated with a precision switch mode / chopper
> circuit, and as the ratios on a transformer are very stable, you only have
> to measure them once during initial calibration.
> Obviously that is good for ppm ratio accuracy in the SelfCAL procedure.
> So thanks again
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