App note: Analog common and Reference IN-OUT

App note on Murata’s Digital panel volt meters analog common and reference pins. Link here (PDF)

Perhaps the least understood I/O pin on all DMS Series DPM’s is ANALOG COMMON. The confusion surrounding this pin is not unjustified since it should be left open, i.e., have no external connections, in the vast majority of normal meter applications. It should not be routinely connected to the power supply ground/common, nor should it be connected to a system’s signal (analog) ground/common.
Part of the confusion surrounding this pin arises from the fact that on some older Murata Power Solutions DPM’s, ANALOG COMMON must be connected to the system power supply common/return. This is not true for new DMS Series meters. In particular, never ground this pin on any DMS-20 Series meters or any of the 9V-powered meters in the DMS-30 or DMS-40 Series. Doing so will result in erroneous display readings.

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