[Gumstix-users] quick electrical question, connecting measuring amplifier to robostix adc

[Esger A. <esg...@ve...>]

Hi,

I'm working on wiring up a robostix/gumstix combo and hit something I'm not 
entirely sure about, not being an electrical engineer.

the situation is as follows:

1 robostix - gumstix - netstix stack, supplied with 5V

1 measuring amplifier (GSV11), supplied with 24V

5V and 24V are similar but separate power supplies, the 220V going into them 
is the same.

the amplifier has a 10V signal out, the ground/zero of which is the same as 
the ground/zero of the supplied 24V

This 10V needs to be connected to an adc of the robostix, I've done this using 
two resistors to limit the voltage at the adc to 5V.

The question I have is what to do with the ground/zero of the 10V with respect 
to the robostix adc. Just connecting it doesnt seem right, because the 
powersupplies might not have exactly the same zero. And if they do, it would 
be unnecessary anyway?

How do I wire this up without causing possible noise or even damage?

My thought was to connect the ground/zero's of the powersupplies to make sure 
they're the same.

It also may/should be possible to shut off one powersupply but not the other.

thanks,

Esger