Experimental study on the sensitivity and accuracy of electric potential local flow measurements

A measuring system based on potential difference probes is presented which makes possible the determination of very small values of the velocity in liquid metal flows. The resolution limit, the size of the sensor, and the induction of the static measuring field have always been a compromise. These opposite demands were countered with state of the art analog instrumentation, and by meticulously avoiding potential sources of error such as induced noise and thermoelectricity. The present paper instances the flow driven by a rotating magnetic field, in which the scaling of velocity versus strength of the driving electromagnetic force was examined. Measurements of the transition from a Stokes regime to a laminar boundary layer regime demonstrate the improvement in velocity resolution by about two orders of magnitude.