Elastic surface wave pressure gauge and pressure sensor for such a gauge
AssigneeThomson-CSF
InventorsGerard Coussot, Pierre Texier
Life of this patent
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Abstract
The invention relates to elastic surface wave pressure gauges. The gauge comprises a plate on which are located the electronic components of the gauge and a pressure sensor grouping the electromechanical elements on a header having connecting pins. The header is provided with a pressure inlet which traverses the plate. The invention is also applicable to the measurement of the pressures of fluids in order to optimize the supply to internal combustion engines. The pressure inlet is made of a rigid metal header and separately grounded for shielding of the surface acoustic wave electrodes to prevent "pull-in" where the oscillators inadvertantly lock on the same frequency.
Claims13
An elastic surface wave pressure gauge comprising:
- a plug-in unit including two delay lines formed by interdigitated comb shaped transducer electrodes placed on a first main face of a piezoelectric wafer, the wafer resting by its second main face on the periphery of a chamber communicating with a pressure inlet, and
- two amplifier circuits oscillating at two different frequencies, one amplifier being connected to each delay line, the difference between these two frequencies being detected by a mixer stage which supplies a measuring signal indicative of a pressure within said chamber,
- the amplifier circuits and the mixture stage being mounted on a circuit board having a ground plane and provided with connections surrounding an orifice providing a passage for the pressure inlet,
- the pressure inlet being being formed as part of the plug-in unit and being constituted by a metal pipe fixed to a rigid metal header, whose periphery is provided with pins which are inserted in said connections, the pins and metal pipe extending outwardly from the piezoelectric wafer, said header having a support for the piezoelectric wafer between the pins, this support having a central depression communicating with the pipe, the metal pipe and header being electrically connected with the ground plane of the board to provide electrical shielding for minimizing pull-in between the two amplifier circuits oscillating at different frequencies.
An elastic surface wave pressure sensor comprising:
- a pressure inlet, a piezoelectric wafer provided with interdigitated comb-shaped transducer electrodes forming on one of its main faces two delay lines which are sensitive to deformations of the wafer and a wafer support having a cavity linking the other face of the wafer and the pressure inlet, wherein the support is a rigid metal header which is peripherally provided with connecting pins having extensions surrounding a central metal pipe fixed to the header by one of its faces, the metal pipe and pins extending outwardly from the piezoelectric wafer the other face of the header having a depression which is connected to the pipe, the wafer resting on the edge of the depression and between the extensions of the connecting pins the central metal pipe and header being adapted to provide, when interconnected with a circuit board including oscillator circuits for measuring the deformation of the wafer, electrical shielding for inhibiting a pull-in of said oscillator circuits.
Dependencies are inferred from the claim text.