Electronics > Metrology

Has anyone seen a mechanical chopper Keithley 147/148 inside?

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MegaVolt:
Maybe there are some photos? Or does someone have a non-working block to disassemble it?

branadic:
I wouldn't expect that much of a difference to the picture shown here:



-branadic-

branadic:
Curious, I've searched a bit, but couldn't find a mechanical chopper based on piezo beams, while reed relays have at least been considered.

https://patents.google.com/patent/US3320559A/en
https://www.eeeguide.com/chopper-type-dc-amplifier-transformer/

-branadic-

inse:
A time ago I had a HP 425A Microvoltmeter from the late 60‘s, it had a electro-optic chopper.
A motor with a segmented disc rotating between a lightbulb and photoresistors.
Well sealed, there was not much to see from the outside, unfortunately.

branadic:
Fortunately doktor pyta took his broken chopper apart and took some pictures last night.

https://www.eevblog.com/forum/repair/keithley-148-nanovoltmeter-repair/msg3969494/#msg3969494

-branadic-

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