[peter_4059 (Peter)]

Originally Posted by Jeffkop

Yes -ve terminals commoned.

A very good question Peter ... The recommended way would be by way of circuit diagram or circuit tracing the -ve side visually ... In the main most designs will accommodate referencing though. If I was going to try referencing I would measure the -ve output with respect to earth first ... this may or may not provide a voltage ... (if its 0 then the supply -ve is obviously already referenced to ground) ... if its above or below zero then I would get a low value resistor say 10ohms and connect that to the -ve terminal then connect the other end of the resistor to earth ... (if there is any kind of spark remove it straight away) measure the -ve and also the voltage between the + and - ... if all is OK you should have the correct output voltage and very little between the -ve and earth ... you can safely reference the supply -ve to any other reference if this is the case.

Thanks for the info Jeff. The QHY8 power supply is double insulated so does not have an earth connection so not sure if it can be referenced to earth in this way?

Originally Posted by adman

Peter - I ended up running my camera off a 45Ah deep cycle battery - though I'm not 100% sure this solved the problem I thought I had with ground loops. The camera still needed a USB connection to the laptop which was running off the main supply.

If you have the technical skills I would highly recommend running the tests that Jeff has pointed out - would really pay to get it right before you start in earnest.

Adam

Thanks for the heads up Adam - what were you using to power the camera before you opted for the deep cycle battery?

Peter.