In my lab we bought an AD7746 for proximity capacitive sensing. The fact is that checking out other capacitive converters, it is usual to have a "shield" pin that provides the same excitation as the one applied in the capacitors so you can use it to block interferences to your sensor (as in the AD7747). But usually this capacitive converters are for measuring capacitors connected to ground while the AD7746 does not work this way, none of the plates is connected to ground.
My question would be: can I do a "shield" by connecting something (a metal plate, a metal cover for a cable) to the EXCA or EXCB ports? Or it would only add those elements to the capacity conversion?