Measuring and testing – Fluid pressure gauge – Vibration type
Patent
1985-03-11
1986-12-16
Woodiel, Donald O.
Measuring and testing
Fluid pressure gauge
Vibration type
73 32A, G01L 1100
Patent
active
046287396
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention is based on a device for measuring the pressure of a gas like medium in accordance with the type of the main claim. A closed system is known from DE-OS No. 31 26 615 with the assistance of which the pressure of a gas is measurable with a power manometer which acts on a piezoelectric element. This is a closed system, the accuracy of which depends to a high degree upon the tightness of the device and which in furtherance has only a limited measuring range corresponding to the deformability of the hydraulic intensifier. Furthermore, during the deflection of a hydraulic intensifier there is a nonlinear interrelation between electrical signal and pressure, whereby the measuring results may be impaired.
SUMMARY OF THE INVENTION
The device in accordance with the invention with the characterizing features of the main claim is advantageous in that with a low constructive effort a robust and exact measuring system is created. In view of its compact structure the device is particularly suitable for use in motor vehicles, whereby in view of the large measuring range different applications may be realized without additional measures. As particularly advantageous in fields of applications the measuring of the intake pressure of the gasoline-air-mixture in combustion motors in the area beneath 1 bar, the measuring of the tire pressure in the range of about 1 to 5 bar and the measuring of the gas pressure in pneumatic brake systems where pressures in the range of 15 to 20 bar occur.
When measuring pressure with the process used here, a substantially closed system is strived for, since in a closed chamber of the inventive type the sonic pressure is proportional to the static pressure. The result is practically hardly adulterated through a thin conduit to the inlet of the gas to be measured. The device in accordance with the invention permits very rapid measurements with low measuring errors, whereby always a linear interrelation is maintained in the total measuring range to a very high degree.
Advantageous further embodiments and improvements of the device are possible. With respect to the selection of the oscillators, preferably piezo bending oscillators are suitable because the deliver a relative strong output signal in a compact structural mode, however thickness vibrators or shear vibrators are basically useable instead. When designing the device it is advantageous if, with the hollow space for the gas volume to be measured and the opening conduit, they are worked out from metallic support disks for the oscillators or that a slotted annular dis is inserted as a distance disc, whereby the slot defines the gas supply conduit. The assembly of the device can be made in a simple manner by welding along the edge of the support discs.
For eliminating aging and temperature influences on the piezoceramic elements of the measuring device, particularly an electrical compensation is suitable in such a manner that an additional reaction oscillator is provided on the same support disc as the first, selected excited oscillator, whereby the output signal of the reaction oscillator acts in the sense of a compensation for the aging and temperature influences on the output signal of the device. This can be performed immediately in that the output signal of the measuring device is represented as a quotient of the signals of the second oscillator and the reaction oscillator (S.sub.2 /SR); however still more simpler is a compensation circuit with a differential forming, whereby the reaction oscillation signal (SR) is fed through an amplifier and to a regulator which changes the exciting signal (S1) of the first oscillator in such a manner that the reaction oscillation signal is substantially maintained constant. Since the temperature and aging influences act in the same manner with similar oscillators, the signal of the second oscillator (S2) is also influenced in the sense of a compensation by the changes caused by the reaction oscillating signal (SR).
Further details and advantageous f
REFERENCES:
patent: 4535633 (1985-08-01), Schiess et al.
Brauer Ilan
Bruggen Gerhard
Karr Dieter
Rottler Wolfgang
Robert & Bosch GmbH
Striker Michael J.
Woodiel Donald O.
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