Development of a Temperature-Compensated Ultrasonic Liquid-Level Meter

Abstract

Methods to remotely monitor and check underground fuel tanks are strongly needed from the viewpoint of environmental protection. This paper presents our temperature-compensated ultrasonic liquid-level meter. By connecting the meter to a telecommunications network, the liquid level in a remotely located tank can be continuously monitored. In our ultrasonic liquid-level meter, we use a reflection ring at the reference position to compensate for measurement error caused by changes of atmospheric temperature. The maximum measurement error is within ±5mm from −10°C to +20°C at a measurement distance of 2000mm. With regard to long-range measurement accuracy, the maximum error has remained within ±2mm over 1.5 years at a measurement distance of 2200mm. In this paper, the structure of the meter, the reflection ring, the configuration of the detection circuit, the superposed signal of transmission and reception, and experimental results are shown.