You are still going to need a common field between the two datasets (Meter Locations and Meter Measurements).
You mentioned that you only have 6 meters that all of the records in the Flow Measurements table link to. In the Flow Measurements table is their an ID assigned to the 6 meters (I.E. you take a measurement once a month for 10 years at each of the 6 meters for a total of 720 records; 120 of which are for Meter A-1, 120 for A-2, etc.)? If this is the case you can add a column to your Meters point feature class and just populate that ID into each of the 6 records. That would give you the common field you need.