to median of the measurement system exceeding a delta to median threshold an offset difference may exceed the difference threshold and a delta to median value may exceed a delta to median threshold for a number of reasons such as gradual drifting from its previous calibration settings a traumatic event such as the msut being moved and a variety of other reasons continuing with the flow diagram in step s 11 identifier 144 determines whether a difference between the current offset and the reset offset i e an offset difference for a respective measurement system exceeds a difference threshold the difference threshold may be any predetermined offset difference value that is considered too large for the measurement system to continue use if the offset difference exceeds the difference threshold i e yes at step s 11 then at step s 12 identifier 144 identifies the measurement system for non use as shown if the offset difference does not exceed the difference threshold i e no at step s 11 fig2 b or if steps s 11 s 12 are not used processing may then proceed to perform steps s 13 s 14 fig2 b or if those steps are not provided evaluate the next msut fig2 a by repeating the measuring step s 2 replacing step s 3 calculating steps s 4 s 7 and resetting steps s 8 s 10 for each measurement system 90 of plurality of measurement systems 91 if provided steps s 11 and s 12 are repeated for each measurement system 90 alternatively or in addition to steps s 11 s 12 steps s 13.