Comparison of current meters in a tidally dominated flow

Three current meters, a Nell Brown ACM-2, an Interocean S4, and an Aanderaa RCM-4, are compared over a sixteen day interval in a strong tidal environment. The sensor elements of all the instruments were within a two meter length on a single subsurface, taut-wire mooring. All three instruments performed satisfactorily. The response of the ACM-2 and the S4 are nearly identical, while the RCM reflects a poor response to low-energy forcing. The RCM proved adequate for investigating long term, low frequency processes in Puget Sound. A question, however, arises concerning the calibration among the instruments.