Fluidic techniques are utilized to provide a highly sensitive gauge. An open-ended tube is excited by a fluid stream flowing past one end to produce standing waves in the tube. Proximity of a sensed object to the opposite tube end is measured in terms of the frequency of the standing waves. For small displacements of the object from the tube there exists a range of increasing displacement over which the standing wave frequency exhibits a large continuous increase. The standing wave frequency is measured with an acoustic pick up or by monitoring the resulting deflections of the excitation stream. In one embodiment the gauge is employed to measure bore holes wherein temperature reference and orientation reference frequencies are provided by similar oscillators. Processing of the measured frequency is effected by counting the temperature reference and measurement frequencies simultaneously in respective counters and stopping the measurement frequency count after the temperature reference frequency reaches an adjustable predetermined count. The resulting count ratio is a measure of the sensed object displacement, fully compensated for temperature. Alternately, the beat frequency between the measurement and temperature reference frequencies provides partial temperature compensation. In the latter case, a go-no go measurement is achieved by comparing the beat frequency to a fixed clock frequency and actuating an indicator when two beat frequency cycles occur during one clock cycle.
The length of a column of a gaseous or liquid substance or of a solid bar is determined by generating a standing wave of known frequency, wavelength and/or wave velocity in the column or in the bar. The wave frequency is varied until at least two consecutive maxima (antinodes), two consecutive minima (nodes) or a minimum following a maximum of the amplitude of the standing wave have been detected. The length of the column of medium at known frequency and wave velocity of the standing wave generated in that column is computed from the equation where L is the length of the column of medium, C is the wave velocity, F.sub.n is the frequency of the nth maximum and F.sub.n-1 the frequency of the (n-1)th maximum. Apparatus for implementing the method comprises a loudspeaker 1 mounted in a resonance chamber 2 with a tubular acoustic exit aperture 3. The resonance chamber 2 is mounted by a spacer 4 a distance from the pipe 6 containing the column of gaseous or liquid substance whose length must be determined. The spacer 4 also supports the receiving microphone 7. To keep the acoustic pressure constant over the frequency/wavelength range in the resonance chamber, the acoustic volume in this resonance chamber is kept constant by a regulator unit 11 with a control microphone 10.
A method and apparatus for sensing the edge of a web which moves along a surface of a body wherein an acoustic pipe is provided in the body with an opening located so that the edge of the web covers a portion of the opening as a function of the position of the web, an air column in the pipe is caused to resonate so that the resultant acoustic signal has a frequency spectrum which is a function of the portion of the opening which is covered by the web, and the resultant acoustic signal is utilized to provide information relating to the location of the edge of the web. The opening can comprise a series of spaced apertures, some of which are covered by the web, or a continuous slot which is partially covered by the web. The resultant acoustic signal can be analyzed by scanning a range of signal frequencies to determine the location of the edge of the web. A web width sensor comprises a pair of adjacent web edge sensors, one for sensing the location of each web edge, for determining web width.
To improve mass productivity of acoustic position sensing apparatus of the type wherein the position of an object is sensed with respect to a sensing port in an acoustic resonator, acoustic transducers for generating an acoustic signal in the resonator and for sensing the acoustic signal in the resonator comprise a sheet of poled piezoelectric material having electrodes on opposite sides thereof. The sheet is fixed over a transducer port in the acoustic resonator. Mass productivity is further improved by integrating a plurality of such acoustic transducers on a sheet of piezoelectric material by appropriately patterning the electrodes thereon.
The coil comprises a plurality of non-joined turns, each turn comprising a rectangular bottom flat section in a bottom plane and a rectangular top flat section in a top plane and two rising sections. The turns fill almost all of the enveloping surface of the coil, a minimum isolating gap separating the adjacent turns. The top and bottom sections corresponding to one and the same turn are aligned with respect to one another and have a larger width than the width of the corresponding rising sections. The turns constitute a plurality of substantially parallel coil branches, rising sections of two adjacent branches arranged between the two adjacent branches being arranged alternately in a single plane.
An improved plunger for fluid dispensing cartridges used in automated dispensing systems. The plunger helps control the reflection of ultrasonic signals used to sense the position of the plunger as it moves within the cartridge tube. The plunger has a convex bottom, ink-facing surface and a top surface comprising one or more flat, horizontal surfaces. In the preferred embodiment, the horizontal surfaces are concentric steps.
