Development of a System for Testing Universal Current Meters

Abstract

The towing tank is the standard procedure for calibrating current meters. It consists of a straight open channel with stagnant water where a current meter is attached to a carriage that moves on rails along the channel at constant velocities. Basically, the testing procedure consists in towing the current meter at several constant velocities recording both the carriage velocity and the rate of rotation of the current meter rotor. Although this is the standard method, the facilitity required is usually complex and dedicated to this procedure, hence it is not affordable by most of the institutions. This study proposes a low-cost reliable system based on the towing tank method that accounts for a Traction Control Module (TCM), a Data Acquisition Module (DAM) and a Control Software (CST). The TCM controls the movement of a towing car on rails installed along a trapezoidal channel with standstill water, using a step motor, steel cables and pulleys. Steel square tubes and pulleys were used to build the towing car, which supported the current meter and the DAM. The CST controlled the TCM and DAM requesting and sending data through serial RS-232. Tests were performed using vertical and horizontal-axis current meters. The facility enabled to perform tests on velocities up to 2 m s and rotation of the propeller of 25 rps, obtaining the equations for the current meters.