EQUIPMENT AND SUPPLIES--Calibration of Electromagnetic Current Meters In Reply Refer To: August 1, 1988 WGS-Mail Stop 415 OFFICE OF SURFACE WATER TECHNICAL MEMORANDUM NO. 88.13 Subject: EQUIPMENT AND SUPPLIES--Calibration of Electromagnetic Current Meters Several hundred electromagnetic current meters of various manufac- turers and configurations have been calibrated at the Office of Surface Water hydraulic laboratory at the John C. Stennis Space Center (formerly NSTL). This experience indicates that all elec- tromagnetic current meters must be individually calibrated at this facility. There is no standardization in the calibration method- ologies used by the various manufacturers of this equipment and the ratings furnished may not meet Water Resources Division accu- racy requirements. Also, a readout check at zero velocity in a bucket of water does not ensure that the readouts will be correct over the range of velocities. Tests by the Hydrologic Instrumentation Facility's Test and Evaluation Section have shown that the indicated velocity readings of at least some of these devices are subject to substantial change dependent on the air temperature at which the electronics are operated. They also may be subject to change with varying water conductivity. Questions regarding calibration and application of electromagnetic current meters should be addressed to Jack Hardee at FTS 494-1555 (commercial 601/688-1555). Ernest F. Hubbard, Jr. Acting Chief, Office of Surface Water WRD Distribution: A, B, S, FO, PO This memorandum supersedes Surface Water Branch Technical Memorandum No. 81.02.