Here again :)
Next need (same board) is to measure 36-72Vcc, keeping the matter 
isolated (it's a telephone line).

Another guy designed a VFC, optoisolated. To me, it looks like a *very* 
complicated way, so I picked an old opto and a Zener, and arranged it in 
the linear zone... and the simulation looks good enough:

http://cyberdyne.homeip.net/public/sim_4n25_36-72.jpg

What do you think about it?

Again needed precision is not much, 2-3%. Speed, once in 10 seconds...

-- 
Ciao, Dario
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