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

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aronake:
I have been reading though lots of SSR data sheets.

Seems G3VM-81GR1 is a good choice for voltage measurement up to 80 V. Leakage current max 1 nA (close to 0 typically). Downside is resistance up to 25 ohn (16 ohm typical), but that does not matter for voltage.

https://www.mouser.kr/datasheet/2/307/en_g3vm_81gr-2583855.pdf

It also have very low "Capacity between terminals".

For a low ohm version, G3VM-61GR2 seems good. Leak current max 100 nA (0.2 nA typically), 0.7 ohm max and 0.25 ohm typically.

https://omronfs.omron.com/en_US/ecb/products/pdf/en-g3vm_61gr1.pdf

My plan is to make a new card of this kind (already have one with G3VM-61VY3). Short out the sense and 2 wire relays (so signal only go though 1 relay) and have 16 channels with G3VM-81GR1 for voltage measurement and 4 channels with G3VM-61GR2 for temperature (with termistor) and 2 wire ohm measurement

voltsandjolts:

--- Quote from: aronake on June 25, 2022, 10:43:40 am ---Seems G3VM-81GR1 is a good choice for voltage measurement up to 80 V. Leakage current max 1 nA (close to 0 typically).

--- End quote ---

Nice find. Indeed the datasheet graph shows typical leakage as 10pA at 80V, 5pA at 40V :-+

Doctorandus_P:
Except maybe that some of those G3VM chips go over USD20

https://octopart.com/search?q=g3vm

Is that considered "normal" for a package with two fet's and a diode, or is it a result of the chip shortage?

Ever since "marketing" has been invented some 150 years ago the correlation between what it costs to make something, and what you need to pay that same something has become ever more fuzzier. In these modern times the difference can be all over the place.

But it does not really feel "right" to me that a simple SMPS IC for example costs EUR3 if you buy it form a "western" brand, while a similar chip costs 30ct or less if it's from a local Chinse manufacturer and you buy it from LCSC.

voltsandjolts:
Yes, expensive now thanks to chipageddon.
But that is being discussed elsewhere, please keep this thread on topic.

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