Abstract: An acoustic sensing system to measure an interior characteristic of an object, for example, density, the presence of defects, or bond integrity (of a laminated object). The system includes a first set of acoustic transducers acting as transmitters for transmitting acoustic wave energy at a single frequency, which acoustic wave energy interacts with the object in a sensing region to provide transmitted, scattered, and reflected wave energy. A transmitter mounting mechanism allows the transmitters to be positioned in such a way that acoustic energy reflected from the object sets up a reverberation between the transmitter and the object. A second set of acoustic transducers acting as receivers of acoustic wave energy is positioned opposite the transmitters in such a way that acoustic waves passing through the object are coupled to the receivers.

Abstract: A scanning system for monitoring the thickness, profile or other data from a moving product which includes a frame for mounting scanning transducers. The product is carried on a conveyor or the like through the frame and the transducers are mounted for transverse scanning motion across the top and bottom surfaces of the product at right angles to its direction of travel. Reference wires are connected between the side members of the frame and maintained at a constant tension independent of ambient temperatures. Reference wires are located between the transducers and both the top and bottom surfaces of the product. The wires provide a constant reference to detect distortion of the frame due to thermal or other stress and to provide correction data which is used to compensate for frame irregularities.

Abstract: A capacitive transducer including a back plate and a tensioned dielectric diaphragm with a conductive layer is operated as a sonic energy emitter and receiver. The polarity of the dc bias applied to the transducer is periodically reversed to prevent charging and polarization of the dielectric diaphragm due to the applied electrostatic field. The bias voltage polarity is controlled in timed sequence with the application of a fluctuating voltage to generate sonic energy with optimum efficiency. Electrical signals resulting from received sonic energy are selectively inverted and provided with compensation for differences resulting from differences in bias polarities.

Abstract: A method for calibrating a thickness measuring system that automatically compensates for inadvertent movements of the probe. In one emobodiment, a conventional thickness measuring system is provided that incorporates a pair of spaced apart opposing ultrasonic sensors that are positioning a known distance apart. A target is passed between the sensors and the distance from each sensor to the target is measured. The thickness of the target can be determined by subtracting the distance from each sensor to the target from the known distance between the targets. The improvement, being a method of periodically checking the distance between the sensors to compensate for movements of the sensor relative to each other due to such effects as thermal expansion or inadvertent movements. The automatic compensation technique can be applied to a single probe system as well.

Abstract: Ultrasonic apparatus for use in detecting an object having a transducer. The transducer has an array of at least one element coupled directly into air. The apparatus also includes a transmitter which may be multi-channel, a receiver which may be multi-channel, a transmit receive switch, and a computer for causing operation of said transmit receive switch to cause sequential supplying of pulses of energy from the transmitter to the element or elements of the transducer and for receiving energy received by the transducer. The element or elements of the transducer are provided with a roughened surface to produce high frequency ultrasonic energy.

Abstract: Ultrasonic apparatus for use in detecting an object having a transducer. The transducer has an array of at least one element coupled directly into air. The apparatus also includes a transmitter which may be multi-channel, a receiver which may be multi-channel, a transmit receive switch, and a computer for causing operation of said transmit receive switch to cause sequential supplying of pulses of energy from the transmitter to the element or elements of the transducer and for receiving energy received by the transducer. The element or elements of the transducer are provided with a roughened surface to produce high frequency ultrasonic energy.

Abstract: A method for calibrating a thickness measuring system that automatically compensates for inadvertent movements of the probe. In one embodiment, a conventional thickness measuring system is provided that incorporates a pair of spaced apart opposing ultrasonic sensors that are positioning a known distance apart. A target is passed between the sensors and the distance from each sensor to the target is measured. The thickness of the target can be determined by subtracting the distance from each sensor to the target from the known distance between the targets. The improvement, being a method of periodically checking the distance between the sensors to compensate for movements of the sensor relative to each other due to such effects as thermal expansion or inadvertent movements. The automatic compensation technique can be applied to a single probe system as well.

Abstract: An ultrasonic transducer and method for detecting the distance to an object using ultrasonic energy. The transducer includes a foil which creates ultrasonic energy. First and second reference surfaces are provided which are spaced between the transducer and the object. The two reference surfaces provide for immunity against temperature and positional changes.

Abstract: Ultrasonic transducer assembly having a piston with a substantially planar surface formed of a conducting material. An insulating foil element having first and second surfaces overlying the substantially planar surface of the piston. The foil has a conducting layer carried by the first surface. A plurality of spaced apart support elements are disposed between the substantially planar surface of the piston and the second surface of the foil.