Milltronics Ltd.

Endress+hauser Gmbh+co.

Siemens Milltronics Process Instruments, Inc.

Bogdan Cherek

Stanislaw Bleszynski

Stanley Panton

Henry T Viuhko

William J Brown

John E Gillis

John Joseph Lee

Son C Nguyen

Jean-Pierre Pawliw

Peter Kloefer

Andy Adams

A pulse-echo ranging system is described employing a microwave transducer head ( ) providing an echo profile output signal which is largely compatible with receivers ( ) and echo processing systems ( ) designed for acoustic transducers. The transducer head employs novel microwave pulse generators ( ) each utilizing a microwave cavity ( ) excited by an avalanche discharge through a small signal diode (D D ) initiated by avalanche of a driver transistor (TR TR ) by a trigger pulse. Repeated pulse from one generator ( ) are transmitted by an antenna ( ) towards a target, and return are mixed with pulses from the second generator ( ) which are subject to a progressively swept delay relative to the transmitter pulses. The mixer output is applied to a tuned amplified ( ) to extract components at an alias frequency related to the sweep rate of the delay relative to the transmitter frequency. The aliased signal is passed to a receiver ( ) and echo processing system ( ).

Microwave pulse generator and pulse-echo ranging system

The invention relates to an apparatus for transmitting radio-frequency signals using a signal generation unit ( ), a signal line ( ), a radiating element ( ) and a waveguide ( ) which is terminated in an end region by a back wall ( ), where the signal generation unit ( ) generates the radio-frequency signals, where the signal line ( ) routes the radio-frequency signals to the radiating element ( ), and where the radiating element ( ) projects into the waveguide ( ). The object is achieved by virtue of the radiating element ( ) being arranged at an angle to the back wall ( ) of the waveguide ( ) or to a plane of the waveguide ( ) which is parallel to the back wall ( ).

Apparatus for transmitting radio-frequency signals

Method of detecting characteristics of liquids in pipes and pump

A vibrating probe for detecting a threshold level within a vessel of fluent material, particularly a liquid, includes: an ultrasonic acoustic transducer assembly comprising a transducer element having a natural resonant frequency, and loading elements effective to shift that frequency to an effective resonant frequency of the assembly, the assembly being supported within the vessel and including a coupling member to couple the transducer acoustically to liquid reaching the threshold level, a transmitter generating pulses applied to the transducer element for repeatedly exciting the transducer element to cause the transducer assembly to resonate at its effective resonant frequency, a circuit for measuring the effective resonant frequency of the transducer over a ringdown period following cessation of each pulse, and a circuit for comparing the effective resonant frequency measured during the ringdown period following each pulse with a predetermined threshold level. The threshold level is selected so as to distinguish between the effective resonant frequency of the assembly in free air and a lower effective resonant frequency when coupled to fluent material through the coupling member. The damping effect of the fluent material, particularly if a viscous liquid, may accelerate the ringdown to an extent such that vibration is effectively suppressed before the end of the frequency measurement, thus further depressing the apparent measured frequency.

Level detector for fluent material

A vibrating probe for detecting a threshold level of solids within a vessel consists of an ultrasonic acoustic transducer assembly having a resonant frequency, the assembly being supported within the vessel and including a coupling member to couple the transducer acoustically to the solids at the threshold level, a transmitter for generating repeated bursts of high-frequency electrical energy and applying them to the transducer, the bursts being of sufficient amplitude to render the assembly self cleaning of adherent solids, a circuit for measuring the amplitude of ringing of the transducer after cessation of each burst, and a circuit for comparing the amplitude of such ringing at a predetermined interval after a burst with predetermined threshold level. Both the predetermined interval and the threshold level may be selectable.

Level detector for solids

A piezoelectric liquid level switch is provided which can be made immune to standing wave effects and provides an unequivocal response to liquid contact. The switch incorporates an electrical oscillator circuit including frequency defining elements in both feed forward and feedback circuit paths, the frequency defining element in the feedback path being a piezoelectric crystal device constructed to have a lowest frequency vibration mode in air which is substantially equal to a first frequency defined by the frequency defining element in the feed forward circuit, which mode is suppressed by acoustic coupling of the device to a body of liquid such that a lowest frequency vibration mode of the device when in contact with liquid has a second frequency which is substantially above the frequency of the frequency defining element in the feed forward circuit, whereby positive feedback through the oscillator circuit can occur when the piezoelectric device is in contact with air, but not when it is in contact with liquid, and a threshold circuit for detecting an output from the oscillator circuit at said first frequency. The piezoelectric element is preferably coupled to a column coaxial with it, the column having a liquid contacting member at its free end, such that a vibration antinode at or near the liquid contacting member is suppressed and the lowest resonant frequency of the device is substantially increased when the member is in contact with liquid.

Liquid level switch

A transformer used to connect an electro-acoustic transducer to a transmitter and a receiver in a pulse-echo ranging system has a first winding connected to the transducer, and second and third windings connected in parallel to the transmitter and the receiver. The second winding has back-to-back diodes in series with it, and the third winding has several times more turns than the second winding, so that with high amplitude signals, as during transmission, the diodes conduct and render the second winding effective. With low amplitude signals, as during reception, the diodes isolate the second winding and the third winding acts to provide a relative step-up of the amplitude of the received signals.

Matching transformer for ultrasonic transducer

A piezoelectric acoustic transducer for coupling acoustic energy to a gaseous atmosphere in a pulse-echo ranging system has a tubular housing closed at one end by a thin integral wall to which a radiating plate of a transducer assembly is coupled to radiate acoustic energy by means of a layer of acoustically transmissive matching material. The transducer assembly except for its radiating surfaces is wrapped in an acoustic decoupling material such as cork, and the side wall of the tubular housing, which has a mounting ring behind the transducer assembly, is also internally lined with such material, space around and behind the transducer assembly within the housing being filled with a slightly elastomeric potting compound. This arrangement decouples the mounting ring from the transducer assembly, thus stabilizing the ringing characteristics of the transducer.

Acoustic transducer

A flexural mode acoustic transducer system for use in pulse-echo ranging systems has a radiating plate of which even-numbered antinodal zones, counting from a drive connection to a driving element at the center of the plate, are formed with rings of apertures to reduce the radiating areas of those zones, thus reducing cancellation in the far field, and improving the matching of the device to the atmosphere into which the plate is radiating. The plate is backed by a sound deadening layer on a flange of a transducer housing, from which it is separated by a foil which is non-adherent to the plate, and is preferably covered by an acoustically transparent fabric having a pore size small enough to exclude damaging particulates.

Growing community of inventors

Peterborough, Canada

Bogdan Cherek