This datalogger manual has a warning about excessive commonmode voltage on its 5th page.
...data acquisition device you have purchased and are about to use is NOT an ISOLATED product. This means that it is susceptible to common mode voltages that could cause damage to the device.
I'm planning to use a metal enclosure which will include some power supplies couple of amplifiers and this logger. Basically two amplifier's will be connected to this logger as single ended. The signal to the amplifiers will come from two transducers 15 meters away from the enclosure by BNC cables. The system already prepared and has its own protection and earthing. I just need to move the system to a new enclosure plus this datalogger.
My questions are following:
1-) If I measure the commonmode voltage as they suggest and warn on 5th page and find out it is alright is there still a risk in another environment for the same setup? I mean I will check comonmode in workplace but some other technicians will install it to a harsh environment for measurements. So should they also check the commonmode voltage there before setting and powering up?
2-) The manual says the common mode voltage might damage the logger. How about if I add 15V zener clamps before the inputs to the logger, wouldn't that protect the logger? Or if there is common mode voltage how to eliminate it?
3-) The transducer amplifier system (the signal source) must be earthed because of lightning protection ect. But logger also in the manual says to be earthed. I'm wondering in that case would there be ground loops. Is this logger's earth connected to its analog ground or analog ground and earth are isolated? Can I verify it and be sure by continuity test?