This is not the best forum to ask how to use the MultiLog2, because this is Siemens user forum.

With regard to interfacing to the Siemens Mag 8000, there are two pulse outputs, at least one of which can be a volume pulse.  The volume pulse output is NOT a pulse frequency output that would be proportional to flow rate.

A volume pulse is generated for a given configured volume passing through the flow meter.  In the receiver, typically a counter is used to accumulate and count the volume pulses to get a total flow value over time.   The receiver can back calculate a flow rate by checking the volume over a given period, like a minute, to get Liters per minute.  You'll have to research what the MultiLog2 functionality is for using volume pulses.

See pages 101 & 102 of the Mag 8000 manual for volume pulse details.

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The electrical specs for the Mag 8000 pulse output can be found on page 40 of the manual.