Development of an acoustic tube based level switch

The level switch is one of crucial devices for measuring for liquid quantity and/or particle stock in a tank. In this paper, we describe a development of new acoustic tube based level switch. The proposed level switch is only employing an acoustic tube and actuator is speaker without extra sensing device by measuring impedance of the speaker. In order to detect level change by using an acoustic tube probe, we have newly developed phase detection based circuits instead of magnitude based detection which enables robust and stable detection. Validity of proposed acoustic tube based level switch is confirmed by applying to detect both grass wool and wood board.