Measuring and testing – Liquid level or depth gauge
Patent
1990-02-16
1991-08-27
Yasich, Daniel M.
Measuring and testing
Liquid level or depth gauge
G01F 2328
Patent
active
050422987
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a filling-level indicator for fuel tanks and comprising a sonic transmitter, a sonic receiver, and a transmitting body extending into a fuel tank. It is already known to introduce sound into a sound-conducting solid body and determine the variation in the propagation velocity (phase velocity) of flexural waves with a receiver. The propagation velocity of the flexural waves in the solid body is a function of the height of the fluid level. The propagation velocity in the solid body in an empty fluid vessel serves as a reference value. Additional measurements are necessary to obtain this function. Furthermore, the transmitter and receiver should not come in contact with the fluid, otherwise disadvantages arise due to deficient sealing of the transmitter or the receiver or inadequate resistance of the points of adhesion. Also, the zero point and the measuring sensitivity of the filling-level indicator are temperature-dependent.
SUMMARY OF THE INVENTION
The object of the invention is to provide a filling-level indicator, having a very high accuracy of measurement and in which influence of temperature on the zero point and on the measuring sensitivity of the filling-level indicator is largely eliminated. The object of the invention is achieved by providing a transmitting body made of a material the temperature coefficient of modulus of elasticity of which, with an opposite sign, has substantially the same order of magnitude as the temperature coefficient of its linear extension. Thus, there is no longer any need for a reference stage or for a computational correction in an evaluation unit, this involving a high outlay. It is possible to do without a hitherto necessary additional determination of the influence of a temperature on the transmission body.
The present invention both as to its construction so to its mode of operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of preferred embodiment with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows schematically a longitudinal sectional view of the filling-level indicator according to the invention, and
FIG. 2 shows a measurement diagram.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1, 10 denotes a tank for the fuel of a motor vehicle, into which projects a transmitting body in a form of a sound conductor 11, of a filling-level indicator 12 for the quantity of fuel in the tank. The sound conductor 11 has a transmitter 13 and a receiver 14 at its upper end projecting out of the fuel. The transmitter 13 is designed as a transducer especially for ultrasonic waves. Both the transmitter 13 and the receiver 14 are arranged above the maximum filling height L of the tank 10, so that neither extends into the fuel. The effective filling height of the fuel in the tank 10 is designated by h. The transmitter 13 and the receiver 14 are connected to an evaluation device 15 not shown in detail.
The transmitter 13 excites in the sound conductor 11 sound waves 17, so-called flexural waves, that is to say transverse waves, the propagation velocity of which is frequency-dependent. Flexural waves are solid-borne sound waves on plates or bars, the oscillating particles of which are moved essentially perpendicularly to the plate plane and in the propagation direction. Furthermore, their propagation velocity in the region of the filling height h of the fuel is substantially lower than in that region L-h of the sound conductor 11 surrounded by the air above the fuel. As shown in FIG. 1, the sound waves 17 come in contact at the transitional surfaces 18 with the particular medium surrounding these. The propagation velocity of the sound waves 17 is determined by the size of the transitional surface 18 and is dependent on the geometrical form of the sound conductor 11. Depending on the filling-level height h, there is a greater or lesser variation in the propagation velocity (phase velocity) of the flexural wave
REFERENCES:
patent: 2910999 (1959-11-01), Kimberly
patent: 3133442 (1964-05-01), Werner
patent: 3229523 (1966-01-01), Boyd et al.
patent: 3512400 (1970-05-01), Lynnworth
patent: 4213337 (1980-07-01), Langdon
patent: 4602505 (1986-07-01), Kanda et al.
"New Instrumentation for Road Tankers", Measurement & Automation News (SIRA), (10-12)/1984, No. 54, 4 pages.
Grein Nicolas
Muller Klaus
Robert & Bosch GmbH
Striker Michael J.
Yasich Daniel M.
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