4,159,646 7/1979 Paulsen et al. 4 170,144 “V1979 Scott ___________ __
reference echo pulses. Means are provided to determine the transit time of pulses along the center path, and also to determine the transit time along the side path. The
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ULTRASONIC LIQUID LEVEL METER
4,470,299
2
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to compensate for environmental changes, thereby to
produce an accurate reading of liquid level.
overcoming the drawbacks incident to prior art refer
ence re?ectors.
of liquid level.
More particularly, an object of this invention is to provide a meter of the above-type in which compensa 10 tion is effected by a re?ector ?xedly positioned to inter In an ultrasonic liquid level meter of the echo-ranging cept and re?ect energy from a side portion of the radia type, pulse of ultrasonic energy transmitted from a sta tion ?eld pattern of the transmitted beam to produce a tion placed above the liquid and re?ected thereby to reference signal which in no way interferes with the produce echo pulses which are received at the station. main liquid level signal derived from transmitted energy By determining the round trip transmit time of the pulse in a path normal to the surface of the liquid. energy in the gaseous medium above the liquid suface, Also, an object of the invention is to provide a com which transit time depends on the distance between the pensated ultrasonic liquid level meter which is of rela station and the surface, one is able to provide a reading tively simple and inexpensive design and which affords
FOREIGN PATENT DOCUMENTS
1329765 12/ 1961 France .............................. ._ 367/908
level of liquid independent of changes in the gaseous
environment,
A signi?cant feature of the invention is that the refer
BACKGROUND OF INVENTION This invention relates generally to ultrasonic liquid level meters of the echo-ranging type, and more partic
5 Claims, 3 Drawing; Figures
0765659 9/1978 U.S.S.R. ......................... .. 73/290 V
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ularly to a meter that is compensated for environmental
ence re?ector means do not obstruct or distort the ultra
sonic energy in the liquid level measuring path, thereby
of liquid in an open channel or other liquid container. The system includes an ultrasonic transducer disposed
The accuracy of an ultrasonic liquid level meter of 20 in environmental conditions. the echo-rБайду номын сангаасnging type is adversely affected by environ Briefly stated these objects are obtained in an ultra
4,470,299
Sep. 11, 1984
Primary Examiner—Daniel M. Yasich Attorney, Agent, or Firm-Michael Ebert
, [57] ABSTRACT
[73] Assignee: Fischer & Porter Company, Warminster, Pa. [21] Appl. No.: 337,082
ratio of the reference side path and center path transit
4:2lO,967 7/1980 Massa ......................... .. 73/290 v x
times is computed to Provide an Output representing the
[22] Filed:
[51] [52]
An ultrasonic echo-ranging system adopted to measure the level of liquid in an open channel or other liquid
container. The system includes an ultrasonic transducer
United States Patent [191
Soltz
[54] ULTRASONIC LIQUID LEVEL METER [75] Inventor: Daniel J. Soltz, Norristown, Pa.
[11] [45]
Patent Number: Date of Patent:
sound in air at 0° C. is 1,087.42 fps, whereas in carbon 25 at a ?xed position directly above the liquid surface, the dioxide it is 1,106 fps. When a meter is installed in an nature of the gaseous environment therebetween deter environment in which the chemical nature of the gase mining the velocity of ultrasonic energy propogated therethrough. The transducer is excited to emit periodic ous medium undergoes change, this factor will disturb pulses which are directed along a center path toward the level reading unless means are provided to compen the liquid surface and re?ected to produce liquid echo sate or correct therefor. Similarly, changes in the tem pulses which return to the transducer and are detected perature of the medium or in ambient pressure ad thereby. A reference re?ector at a predetermined posi versely affects the accuracy of the instrument.v tion relative to the transducer intercepts energy from a In order to provide a reading in an echo-ranging side path in the radiation pattern of the transducer to liquid level meter, which is independent of changes in return it to the transducer to produce reference echo the propogation medium (air or other gas), the US. Pat. pulses. Means are provided to determine the transit time No. 3,834,233 to Willis et a1 discloses a ?rst transducer along the side path. The ratio of the reference side path mounted on top of a tank to direct sound energy down and center path transit times is computed to provide an into the tank and to detect an echo from the surface of