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Example Project: 20 Channel solid state scan card for K2000 DMM

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voltsandjolts:
I have previously posted a 10 channel armature scan card here:
https://www.eevblog.com/forum/circuit-studio/example-project-relay-scan-card-for-k2000-dmm/

I needed more channels for a particular job where a little SSR channel leakage wouldn't be a problem, here is the result.
It's been tested in K2000 and DMM6500.
It's switchable, 10 or 20 channels; some 2000 series gear might only support 10 channels (?), and saves some money if you only need 10 channels.
Initially I thought my K2000 would only support 10 channels but to my surprise the 20 channel card is supported too - at least it is in the latest firmware.

The PIC MCU firmware has a known issue when using with a DMM6500.
Switching between 2W and 4W resistance on the same channel causes the channel relay to open.
It works fine changing between channels in 2W and 4W.
I just need voltage measurements so didn't spend time fixing it, there's a note in the firmware source.

Thanks to forum members alm and cozdas for providing some background information and inspiration.

Edit:
I expect this card will NOT work in a K2001, K2002 or K2010 DMM for reasons described in this post.

FYI I adapted this card design to function in the Keysight 34970A/34972A DAQs, see here.

voltsandjolts:
CircuitStudio Project attached in 7-Zip format

jaudo:
Looks amazing!

I'm starting with Circuit Studio. I've seen you are manufacturing with JLPCB. Could you export the .rul file for us (if it's designed for JLPCB manufacturing?) this would save me a lot of time. :)

voltsandjolts:
I was quite lazy about rules in that project, probably better to use this:
https://github.com/ayberkozgur/jlcpcb-design-rules-stackups

Yansi:
The "spare SSR" area on the board is funny.  :clap:

Also quite surprised about the claimed <1nA typical leakage of the SSR in off state.  (but still it doesn't beat a proper reed relay) :)

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