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Proceedings Paper

High-accuracy liquid level meter based on pulsed time of flight principle
Author(s): Kari E. Maatta; Juha Tapio Kostamovaara
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Paper Abstract

A prototype of a liquid level gauge based on pulsed time-of- flight method was developed for measuring liquid level accurately at distances from zero to 30 meters. The system consists of an optomechanical sensor head and electronics unit which are connected to each other by means of two optical fibers. The developed level gauge utilizes mirror- like reflection of the liquid surface and by proper design of the optics the received signal is constant in the whole measurement range. The losses in the optical path of the level gauge are relatively small, thus allowing the use of a 1 mW CW semiconductor diode laser as a light source. The pulsing frequency of the laser is 1.5 MHz and the time interval between start and stop pulses is digitized by means of a simple and inherently linear synchronous digital counter. The correct orientation of the measurement head is achieved by using sensitive bearings and by allowing gravity to keep the correct orientation. An attenuation system based on eddy currents effectively attenuates the oscillation of the sensor head. Measurements carried out in laboratory show that the accuracy of some millimeters can be achieved with the measurement time of some seconds.

Paper Details

Date Published: 25 September 1997
PDF: 10 pages
Proc. SPIE 3100, Sensors, Sensor Systems, and Sensor Data Processing, (25 September 1997); doi: 10.1117/12.287754
Show Author Affiliations
Kari E. Maatta, Univ. of Oulu (Finland)
Juha Tapio Kostamovaara, Univ. of Oulu (Finland)


Published in SPIE Proceedings Vol. 3100:
Sensors, Sensor Systems, and Sensor Data Processing
Otmar Loffeld, Editor(s)

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