Application of TDR to Measurement of Average Water Level in Periodic Wave

Abstract

To find a robust method for water level measurement based on time domain reflectometry (TDR) under periodic wave conditions, an experimental water level measurement installing the noise filter function in TDR cable tester was conducted and the function effectiveness was examined. In the experiment, changes in water level from the tip of TDR probe were measured in the experimental channel where water surface fluctuations caused by wind, rain, or water current were artificially reproduced with a paddle. In low noise filter level (NFL), TDR waveforms obtained in the water level measurements swayed responding to the water surface fluctuations. In high NFL, the sway was restrained, and it disappeared when NFL was highest of 128. Moreover, most water levels h_TDR evaluated from the waveforms obtained in NFL= 128 were agreed with averaged water levels h_ave, although h_TDR overestimated h_ave under low level conditions. However, the errors under low level conditions could be corrected by the linear function based on h_ave-h_TDR relationship.