Electro-Magnetic Velocity Meters: Assessment of the (Missing) Technical Parameters

Abstract

Flow measurements in Urban Drainage Systems are essential for the pollution control. Since the accuracy of the Acoustic Doppler Velocimeters is impeded by several factors, this research is focused on the alternative or a supplemental Electro-Magnetic Velocity (EMV) meters. EMV meters are more robust and reliable and can provide accurate measurements of low flows or even under a porous sediment cover. However, the downside of their usage is the small control volume (CV) where the flow velocities are integrated in a non-linear manner to obtain a single one-dimensional velocity measurement. To provide accurate mean flow velocity it is necessary to determine the size of the CV and to understand the non-linear integration principle within the CV. These valuable data are typically not provided by the manufacturer. In this paper, an experimental methodology is proposed for defining the size of the CV and the one-dimensional (1D) weighting function, used to describe the sensor’s integration principle. In the experiments, bed-mounted flat DC2 EMV probe was used. The size of the CV and 1D weighting function were determined based on the results of the EMV operation under sand cover of varying depth. It was shown that the reach of the CV for the used device is 6 cm from the electrodes of the sensor.