Measuring and testing – Volume or rate of flow – Expansible chamber
Reexamination Certificate
1998-10-29
2001-05-22
Williams, Hezron (Department: 2856)
Measuring and testing
Volume or rate of flow
Expansible chamber
C310S316020, C310S317000
Reexamination Certificate
active
06234017
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a transducer assembly and in particular to a transducer assembly adapted for the pulse-emission of a signal.
This invention also relates to a method of comparing a first condition within a container and a second condition within said container by means of such a transducer system.
Transducer assemblies are known in which a signal is generated by way of a cable and a step-up transformer. The need to provide a high peak power in such an assembly restricts the choice of wire used for the cable.
The applicants have now devised a transducer assembly in which only the average power need be delivered along the cable, which can operate at a low voltage and low current, which is capable of considerably enhanced resolution and which can be used in hazardous areas (for example to determine the level of a flammable substance in an enclosed vessel).
SUMMARY OF THE INVENTION
In a first aspect, the present invention provides a transducer assembly adapted for the pulse-emission of a signal, the assembly comprising:
(a) a transducer;
(b) a drive-circuit for the transducer (a), in which the drive-circuit includes a charge storage device, a wound coil assembly and at least one switching element, all components of the drive-circuit (b) being operatively associated with one another and with the transducer (a).
Suitably, the transducer (a) comprises one or more surfaces (e.g. of a ceramic material) which are capable of exhibiting a piezo-electric effect.
Preferably, the transducer (a) is an air-transducer.
Preferably, the charge storage device comprises a capacitor, for example a capacitor having a capacitance in the order of 1000 &mgr;F. The capacitor may be operatively associated with one or more batteries.
Alternatively, the charge storage device may comprises one or more batteries, with the capacitor being omitted.
The wound coil device may comprise one or more windings wound on a magnetic core, in the manner of a transformer, and conventionally termed an inductor due to the presence of a gap in the magnetic core and therefore deliberate energy storage within the device. Preferably the inductor has an inductance in the order of 1 mH. Suitably, the inductor may be adapted to resonate with the transducer (a) at a selected frequency or over a selected frequency-range.
The inductor may be provided with any number of tap points (including none), the principle purpose of which are to control the proportion of the transducer peak voltage that is presented across the switching elements.
The switching elements will preferably comprise semiconductor devices. At least one switching element is required, and in this simplest configuration the switching element is closed in order to build up a current in the inductor, and opened in order to redirect this current onto the transducer.
A further switching element can be added, in conjunction with a dissipative element, or resistance, in order to dissipate the pulse energy after a defined time, this has the effect of curtailing the duration of the sound pulse.
Further switches can be incorporated in order to recycle some of this energy.
In a second aspect, the present invention provides a method of comparing a first condition and a second condition of a container, in which one or more parameters of each said condition is measured by means including at least one transducer assembly according to the first aspect of the present invention, hereinabove described, and the results of each said measurement are compared by means of a comparison system operatively associated with said transducer assembly.
For example, the first condition of the container may correspond to the situation wherein the container is empty and the second condition may be may correspond to the situation wherein the container is at least partly filled. The first condition may be determined by a single measurement if the vessel is empty, or may be determined incrementally as the vessel empties.
Preferably one of the two conditions is taken as a “base” or “reference” condition for the composition. For example, the empty condition of a container (such as a silo) may be expressed to be the “base” or “reference” condition and the filled or partly-filled condition may then be expressed as being relative to that “base” or “reference”.
Comparison of the two conditions may be achieved by means of systems which are well known to those skilled in the art to which the present invention relates.
The present invention will be illustrated, merely by way of example, in the following description and with reference to the accompanying drawings.
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Smith Colin
Stevens Kevin
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Miller Rose M.
Pulsar Process Measurement Limited
Williams Hezron
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