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