EQUIPMENT & SUPPLIES--Marsh/McBirney model 201 electromagnetic meters; need to check manufacturer's calibrations




In Reply Refer To:                                         November 13, 1980
EGS-Mail Stop 415




SURFACE WATER BRANCH TECHNICAL MEMORANDUM NO. 81.02

Subject:  EQUIPMENT & SUPPLIES--Marsh/McBirney model 201 electromagnetic
          meters; need to check manufacturer's calibrations

A check on the rating calibration of a Marsh/McBirney 201 current meter

in the towing tank at GCHC suggests the need for individually rating these

meters.  Whereas the meter registers zero when there is zero flow, the

manufacturer's linear rating equation has a finite intercept.  The actual

meter readings will therefore depart from the linear equation at the low

velocities, sometimes resulting in sizeable errors.  Use of the Marsh/

McBirney 201 meter for accurate results will require that each meter be

calibrated individually.  Meters to be rated should be sent according to

the standard procedures to the Repair and Calibration Section, Hydrologic

Instrumentation Facility, GCHC, NSTL Station, MS 39529.




                                         Stanley P. Sauer
                                         Acting Chief, Surface Water Branch

Distribution:  A, B, S, FO, PO