Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1989-02-03
1990-07-31
Budd, Mark O.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
310334, 73290V, 73644, 7386118, H01L 4108
Patent
active
049452762
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a transducer for arranging in a fluid for measuring the flow-velocity of a fluid in a pipe, by transmitting/receiving sonic pulses.
TECHNICAL FIELD
The invention is developed especially in connection with the need for and development of a transducer arrangement operating with ultra-sound, for measuring the flow velocity of a fluid in a pipe, comprising two transducers, mounted on their respective sides of the pipe, and directed obliquely in relation to the flow-direction, which alternately transmit and receive sonic pulses to and from each other, however, the invention is not restricted to this specific application, since the new transducer can also be utilized for other purposes, for instance for measuring the fluid level in a container. Hence, when specific conditions for development are described in the following, these are not to be considered as limiting, but merely represent a demonstration of the developmental basis from which progress has taken place. So, as mentioned, the new transducer is developed in connection with a transducer device for measuring the gas flow to a so-called flare in connection with facilities for exploration and production of hydrocarbons. In this connection there is a definite need to be able to cover a relatively large range of flow-velocity in an accurate manner, and at the same time there is a need for safety, particularly in the case of measuring in so-called danger areas.
BACKGROUND ART
The transducer devices which are known today operate with transducers which are mounted and dimensioned for relatively limited velocity ranges. The accuracy of measurement in such devices is not always completely satisfactory.
A particular aim of the present invention is to provide an electroacoustic transducer for application in gasses and liquids in potentially explosive areas where there is a demand for a reliable transducer embodiment which will be able to supply sufficient acoustic energy for various purposes.
DISCLOSURE OF INVENTION
In order to achieve this object, a transducer is suggested according to the invention, which transducer is is designed as a cup-shaped metal body having a base which forms a membrane is assigned an electrode on its inside which is sealed off from the environment that is, from the fluid, and the cup-wall of the body is designed with an annulus filled with a powerful damping material, for example epoxy, rubber or epoxy mixed with metal particles.
Such a cup-formed metal body can be formed, with regard to the utilization of the base as a membrane, by means of suitable machining, and the annulus can also be machined out in a suitable way without particular difficulty. The base designed as a membrane in the cup-formed metal body is connected with an electrode in the form of a piezo-electric driving element with suitable characteristics. The metal cup functions then as the one electrode, while the piezo-electric driving element's free end serves as the other electrode for electric excitation of the transducer.
The operational frequency of the transducer can be selected by choosing suitable dimensions for the piezo-electric driving element and for the thickness of the membrane. Transducers can thus cover both ordinary sonic frequencies and ultrasonic frequencies.
The new transducer is suitable for use in measuring the velocity of gasses and liquids, also in so-called danger areas (where a danger of explosion exists). A metal material for the cup-shaped body is-chosen according to the demands which are made to transducers (environmental requirements). Titanium, steel, aluminium, carbon fiber and other materials can thus be used for the transducer cup.
The annulus can extend from the mounting side of the transducer and out to the same level as the membrane, but it can also extend from the end facing the environment.
The entire cup-formed body can be attached to a supporter on the mounting side in a hermetically sealing manner, so that the electric contacts will not be exposed to the environment wherein the transducer is to oper
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"Theoretical Analysis of the Basic Parameters of Ultrasonic Flowmeters", by N.I. Brazhnikov (Translated from Izmeritel'naya Tekhnika, No. 8, pp. 57-62, Aug., 1966.
Hammer Erling
Mylvaganam Kanagasaba
Budd Mark O.
Den Norske Stats Oljeselskap A.S.
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