32 channel micro relay board

Thread Starter

jismagic

Joined Sep 7, 2013
77
Attached file shows a kind of thing I am doing. I have SSR block always connected to the device. Does that mean there is always a leakage current (however small) still flows through the SSR (when in off state). Does it provide good isolation in that case?
thanks
jis
 

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ebeowulf17

Joined Aug 12, 2014
3,307
Yes, there could be persistent, tiny leakage current (looks like 1 uA for the one we've been discussing.) Not sure what that has to do with isolation - it would leak from your device through SSR to ground, not leak to Arduino. If Arduino shares ground with the ground you're switching with the SSR, that's your decision, but it's not necessary for the SSR to work. Total isolation should be possible.
 

Thread Starter

jismagic

Joined Sep 7, 2013
77
Yes, there could be persistent, tiny leakage current (looks like 1 uA for the one we've been discussing.) Not sure what that has to do with isolation - it would leak from your device through SSR to ground, not leak to Arduino. If Arduino shares ground with the ground you're switching with the SSR, that's your decision, but it's not necessary for the SSR to work. Total isolation should be possible.
i am introducing a new path (however leakage current is small) for which the device is not designed for during its OFF state. That would mean my test equipment is not fully isolated from the device. It is however true that it does not leak to arduino but it leaks from one device(test equipment) to another(device under test) which is an isolation problem.
 

ebeowulf17

Joined Aug 12, 2014
3,307
Hard to imagine what you're testing for where 1uA per input (32uA max if testing 32 inputs) would matter. For comparison, it looks to me like the voltage divider in combination with your supply voltage and pullup resistor leak 71uA per input. Somebody should check my math here, but it looks to me like your device is leaking 71 times as much current as the SSR leakage would add.

If you really need zero leakage, sounds like you will need mechanical relays and you may just have to increase your budget and space allocation.
 
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