On many occassions there is a need to interface a analog signal conditioner, to the ADC input of an MCU systems.

In cases where I source the signal conditioner, I take care to go with well documented ones. But in many a case the customer supplies it and quite often you land with something that has inadequate documentation apart from the basic information whether it outputs 0-10V or 4-20mA or some such span value. In such an event how to find out the following :

1. In a mains operated unit, whether the output is referenced to mains ground or floating ( would a simple ohmic value check between the -ve terminal of the output and the PE pin suffice ? )

2. Source impedance. This is the real problem- you have no idea unless the manufacturer specifies - is there any way to find this out ?

I am currently trying to design 4 such interfaces ( 0-10V range) and any light on the topic would be useful.

Thanks

Raghu