Products > Test Equipment
Krohn-Hite 522 DC calibrator.
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grumpydoc:
I'm not sure I count this as a "score" - it still cost me £94 (= USD 145 or AUD 186) but I spotted a Krohn-Hite Model 522 calibrator on ebay and (as usual) couldn't resist.

Sold as "doesn't power up" - well, not sure about that, it powered up just fine when I unpacked it. There was no output at the front connectors but that was a simple matter of changing the jumpers from rear panel output to front panel output  >:D



Of course it would be nice if the Keithley read 10.00000V but, in fact the above reading is in spec.

The 522 has an accuracy of ±0.002% of the setting plus ± 0.0005% of range plus ± 0.0005% per oC plus ± 2uV giving, for all intents,  ± 25ppm in total (ignoring tempco and the 2uV which is 0.2ppm on the 10V range)

The Keithley's 1 year accuracy is 50ppm of reading plus 35ppm of range giving 85ppm at 10V (and this one hasn't been calibrated recently) so any reading from about 9.999V to 10.001V would be acceptable. Sadly the 522 is not quite accurate enough to check the Keithley and vice versa.

My 2015 says 10.00022V which agrees pretty closely with the 2000 (just 6ppm difference) so I suspect that the 522 is slightly high and either just within it's spec or just out but I can't really tell.

Tear down pics later.

Does anyone know what the difference is between this model and the 521 - the few pictures and specs I can find on the web don't really seem to show any difference at all.

Finally is there a service manual - the manuals on the web all seem to omit the theory of operation and schematics. There's a 521 manual available, but I'd quite like the correct manual if possible.
JohnnyBerg:
Nice score  :-+
matseng:
Oooohhh.... That's a beautiful oldskool display. ^-^
grumpydoc:

--- Quote from: JohnnyBerg on March 01, 2015, 12:11:52 pm ---Nice score  :-+

--- End quote ---
Better than the Fluke 343A which was supposed to be working and cost me twice as much.

It is still, somewhat optimistically, in the repair pile. If I were honest with myself it would be in the "too shagged to be fixable" pile but I live in hope  :)

JohnnyBerg:
I am looking forward to the teardown.  ;)

Especially the reference.

Perhaps, it doesn't need repair? Only calibration?
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