Design and field test of a continuously weighing, tipping-bucket assembly for aeolian sand traps

Abstract

A new tipping-bucket assembly (T-BASS) for aeolian sand traps has been designed and field tested with encouraging results. It facilitates high-frequency monitoring of sediment flux over extensive time periods, and therefore offers improved performance over other continuously weighing mechanisms that are generally limited to either a small total-load capacity or poor resolving ability. The T-BASS is a modified version of the tipping-bucket meteorological rain gauge mounted on a cantilever and pulley system linked to an electronic load cell. As trapped sand accumulates in one of the buckets, the increasing mass exerts a downward force on the cantilever arm, which translates into a slight deflection of the thin-beam element of the load cell. The resulting voltage output is proportional to the load, and the analogue signal may be monitored by a data-acquisition system. Eventually the bucket fills to capacity and tips, the sediment load is emptied into a reservoir container, the other bucket of the bucket pair is positioned beneath the funnel, and the system is automatically reset to zero load for continued measurement. In this way, a high-frequency record of sediment accumulation is obtained. Field testing of five prototypes demonstrated that the T-BASS can be configured to yield: (i) linear calibrations (for conversion of voltage to gram weight) with R2 values exceeding 0·99; (ii) weight resolution of 0·99; (ii) weight resolution of 0·1 g or better depending on load-cell specifications and bucket capacity; and (iii) detailed temporal information (order of 1 s) on sediment flux allowing investigation of its relation to attributes of the wind field. Suggested modifications may produce improved performance in future versions. Copyright © 1998 John Wiley & Sons, Ltd.