Measuring and testing – Fluid pressure gauge – With pressure and/or temperature compensation
Reexamination Certificate
2001-07-17
2004-01-27
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Fluid pressure gauge
With pressure and/or temperature compensation
C073S700000, C073S706000, C073S715000
Reexamination Certificate
active
06681637
ABSTRACT:
The present invention relates to a pressure-measuring cell with a temperature sensor. Temperature sensors are frequently integrated into pressure-measuring cells in order to compensate for the static temperature errors that arise in pressure measurement. In the case of ceramic pressure-measuring cells this temperature sensor is usually applied to the back of the ceramic piece, although it can also be contained in an adjoining electronic evaluating unit. A disadvantage of such pressure-measuring cells is that temperature changes in the medium whose pressure is to be measured—a medium which often acts with direct contact on the pressure-measuring cell—only have an effect on the temperature of the temperature sensor after a considerable delay, and at times in dampened fashion. Any resulting temperature deviation between the medium to be measured and the temperature sensor will lead to errors in the correction of the measured pressure value provided by the measuring cell.
In order to solve this problem the present invention proposes—in a pressure-measuring cell that exhibits a base as well as a diaphragm that is positioned on the base and that is deformed by the pressure to be measured—that a temperature sensor be positioned between the diaphragm and the base. This positioning guarantees that there is a slight distance between the temperature sensor and the medium that exerts a pressure on the diaphragm, so that the measured value of the temperature sensor is able to quickly follow temperature changes in the medium. As a result, the disruptive influence exerted by abrupt temperature changes in the medium on the pressure measurement is reduced considerably.
A typical separating distance between the temperature sensor and an outer diaphragm area that is exposed to the pressure being measured lies between 0.1 and 3 mm, depending on the thickness of the diaphragm, i.e., depending on the dimensions of the pressure-measuring cell or the pressures to be measured by the cell.
In order to assure an efficient heat transfer between the medium and the temperature sensor, it is advantageous to embed the sensor in a material layer that connects the base and the diaphragm.
In particular, it is advantageous to embed the sensor in a seal that seals a compartment formed between the base and the diaphragm.
In a sensor whose base and/or diaphragm consist of a ceramic material, this kind of seal will be advantageously formed by a glass.
The temperature sensor will expediently comprise a resistor element with temperature-dependent resistor. It is easy to manufacturer this kind of resistor element so that it has a flat shape.
In order to receive a temperature-measuring signal that is as large and noise-free as possible, it is expedient for the resistor element to extend over virtually the entire circumference of the measuring cell. A secondary effect of this configuration of the resistor element is that the temperature determined from the resistance value of the resistor element represents a mean value over basically the entire circumference of the diaphragm and thus very closely approaches a mean value over the entire surface of the diaphragm.
In order for it to be possible to house a long conductor for the resistor element on a given circumferential length of the seal, the resistor element will preferably have a meander-shaped design.
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Boehler Ewald
Jacob Joern
Liehr Manfred
Berkowitz Marvin C.
Ellington Alandra
Lefkowitz Edward
Nath & Associates PLLC
Vega Grieshaber KG
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