DC power supply grounding

[r3pp3r]

I want to have a 5 VDC power supply power a comparator circuit I am making, and have a small input signal from a circuit powered by a separate 15 VDC power supply feed into the comparator. Is it acceptable to tie the DC grounds of the two power supplies together to accomplish this task?

 

[itsmoked]

Generally yes.

Contras would be:

1) The two systems are far apart.
2) One is intrinsically noisy.
3) One is EXP
4) Some medical systems
5)

You would only want to connect them at one central location.