JPH0390832A - pressure measuring device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a pressure measuring device that utilizes the fact that the resonance frequency of a piezoelectric vibrator such as a quartz crystal vibrator has a correlation with surrounding pressure.

<Prior art> It is known that the resonance frequency of a piezoelectric vibrator changes linearly depending on the surrounding pressure (Japanese Patent Laid-Open No. 57136130).
Publication No.). However, the constant of proportionality differs depending on the type of surrounding gas or liquid, and it is not preferable to expose the piezoelectric vibrator directly to the outside world because dust and the like will adhere thereto. Therefore,
For example, as shown in FIG. 3, external pressure has been measured using a vibrator having a sealed structure using an elastically deformable body such as a bellows or a diaphragm.

<Problems to be Solved by the Invention> As described above, in conventional examples of sealed structures using bellows, diaphragms, etc., the elastic constants of the bellows or diaphragm greatly affect the internal pressure around the vibrator, and the temperature Changes in the volume of the bellows or diaphragm also affected the internal pressure. Furthermore, since the bellows and diaphragm are made of metal and have a large spring coefficient, it has been difficult to measure minute pressure changes.

<Means for Solving the Problems> The pressure measuring device of the present invention comprises: a sensor chamber provided with a vibrator and filled with a predetermined gas; a first liquid column whose upper end serves as an inlet for introducing the pressure to be measured; a second liquid column that communicates with the first liquid column only at its bottom and whose upper end communicates with the sensor chamber; and a non-volatile liquid filled in the first and second liquid columns; It is characterized in that the pressure at the pressure to be measured inlet is measured from the resonance frequency of .

Function> This will be explained using the principle embodiment shown in FIG. The external pressure to be measured is P, the internal pressure of the sensor chamber is P2, and the cross-sectional area of the liquid column on the external pressure side is S.
If the cross-sectional area of the liquid column on the internal pressure side is S, the liquid level difference is h, and the density of the sealing liquid is ρ, then the internal pressure P2 of the sensor chamber is P, = P, -ρS2h...(1) Measurement If the external pressure P1 increases, the liquid level difference increases, the internal volume V of the sensor chamber decreases, and the internal pressure P2 increases. On the contrary, pressure P
1 decreases, the internal volume V of the sensor chamber expands and the internal pressure P2 decreases.

The gas volume V in the sensor chamber is inversely proportional to the internal pressure P2 when the temperature is constant. Also, since the volume of the sealing liquid does not change,
If the displacement of the liquid level due to pressure change is hh2, S Ih+ = S z h z ...(
2) The larger the cross-sectional area S2 and the space volume of the liquid column on the internal pressure side, the wider the measurement range; conversely, when 82 is small, the sensitivity becomes higher.

<Example> FIG. 1 shows a principle example of the present invention. A tuning fork crystal resonator 2 that performs bending vibration is disposed within the sensor chamber 1, and its electrode lead wire 3 is led out to the outside and connected to an oscillation circuit. The liquid tank 4 includes a first liquid column 41 whose upper end serves as a pressure introduction port to be measured, a second liquid column 42 whose upper end communicates with the sensor chamber 1, and a communication section 43 which communicates both liquid columns at the bottom. The sensor chamber 1 is formed into a substantially U-shape and is filled with an appropriate amount of nonvolatile sealing liquid 5 to isolate the sensor chamber 1 from the outside world. The sealing liquid 5 is preferably a non-volatile liquid such as mercury or silicone oil. For example, another liquid layer such as silicone oil may be provided on the surface of the mercury. Sen.

The chamber 1 is filled with an inert, high-density gas such as an insulating gas SF6 for a high-voltage transformer.

FIG. 2 shows a preferred embodiment of the present invention. The liquid tank 4 has a double cylindrical shape except for the bottom, the upper end of the cylinder 44 communicates with the sensor chamber 1, and the upper end of the outer cylinder 45 connects to the pressure to be measured. It opens at the inlet.

<Effects of the Invention> According to the present invention, a nonvolatile sealing liquid is interposed between the sensor chamber and the measurement pressure inlet, and the external pressure P1 and the internal pressure P2 are balanced through the sealing liquid. , there is no influence of the spring constant of the elastic body, making it possible to measure pressure with extremely high sensitivity and a wide measurement range. Further, by selecting the cross-sectional area of the liquid column and the volume of the liquid column space, the measurement range etc. can be arbitrarily designed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a principle embodiment of the present invention, FIG. 2 is a diagram showing a preferred embodiment of the present invention, and FIG. 3 is a diagram showing a conventional example. Sensor chamber Tuning fork crystal resonator lead wire Liquid tank Sealing liquid

Claims (2)

[Claims] (1) A sensor chamber equipped with a vibrator and filled with a predetermined gas, a first liquid column whose upper end serves as an inlet for the pressure to be measured, and which communicates with the first liquid column only at its bottom, with its upper end above the It has a second liquid column communicating with the sensor chamber and a non-volatile liquid filled in the first and second liquid columns, and measures the pressure at the measured pressure inlet from the resonance frequency of the vibrator. pressure measuring device. (2) The pressure measuring device according to item 1, wherein the cross-sectional area of the second liquid column is larger than the cross-sectional area of the first liquid column.