Evaluation of Common Mode Signal Rejection Algorithm on Ultrasonic Cross-Correlation Flow Measurement

Abstract

Ultrasonic Cross-Correlation Flow Meter (USCCFM) has been used at Darlington Nuclear Generating Station (DNGS), OPG to verify feedwater flow instrumentation uncertainties. Due to piping location at DNGS, there are strong common mode signals presented at the measurement locations. The common mode signals interfere with the USCCFM measurement, and alter the measurement results. A Common Mode signal Rejection (CMR) algorithm is used to remove the effects of common mode signals. A simulation module has been developed in the USCCFM software. The simulations confirm that the CMR algorithm is effective in removing common mode signals; and also reveal that the CMR algorithm introduces a bias to the measurement results. The bias value can be estimated using the simulation. Based on the simulation results, it is concluded that the bias introduced by the CMR algorithm is much smaller than the error coursed by common mode signals.