JPS5967437A - Quartz vibrator pressure sensor - Google Patents

Abstract

PURPOSE:To improve the detection accuracy by detecting a pressure with an oscillation frequency of a quartz vibrator corresponding to a clearance which will be varied according to external pressure as set by separating an excitation electrode thereof from the body thereof. CONSTITUTION:The body 12 of a quartz vibrator supported with a support 11 made of an insulator is grasped with excitation electrodes 13a and 13b leaving a clearance. This sensor is sealed into a pressure container 14 and as a gas P to be measured is introduced from a pressure introduction pipe 14a, the excitation electrodes 13a and 13b deflects to vary the clearance with the body 12 of the quartz vibrator whereby a pressure is detected as variation in the oscillation frequency of the quartz vibrator 12. The detection of the pressure is done by reading changes in the oscillation frequency of the quartz vibrator 21 as reference and that of the quartz pressure sensor 22 with a frequency comparator circuit 23 and the results are indicated on a display section 24 as pressure value of a gas. Thus, the detection accuracy of the pressure can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure sensor that detects pressure, particularly gas pressure, by changing the oscillation frequency of a crystal oscillator.

Conventionally, a strain gauge is used as a typical sensor for detecting gas pressure. This detects the amount of deformation that changes due to changes in the pressure applied to the diaphragm or bellows by using resistance changes caused by the expansion and contraction of resistance wires.This strain gauge and fixed resistor constitute a bridge circuit. This method measures gas pressure, and this method has the following drawbacks.

Power consumption is large. Since the magnitude of the output signal depends on the power supply voltage, fluctuations in the power supply voltage directly affect detection accuracy. In addition, since the output signal is an analog quantity, remote measurement requires
Since the output voltage is greatly affected by the length and resistance of the transmission line, the material, the state of the connections, etc., the accuracy decreases, so there are various restrictions when configuring the system. Many of the various types of sensors other than strain gauges also perform analog detection using changes in resistance, current, and voltage.

These sensors have similar drawbacks as described above.

It is an object of the present invention to solve the above-mentioned drawbacks and to obtain a pressure sensor with excellent detection accuracy.

Hereinafter, details of the present invention will be explained with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which a crystal resonator main body 12 supported by a support 11 made of an insulating material is sandwiched between excitation electrodes 15cz and 15b with a gap between them. . The entire excitation electrode may be a thin metal plate, or the electrode may be provided in a predetermined shape on a thin insulating plate such as glass by vapor deposition, sputtering, or the like. The above-mentioned sensor is sealed in the pressure vessel 14, and the measurement gas is introduced from the pressure introduction pipe 14α, the excitation electrode is deflected, the gap with the crystal oscillator body changes, and the oscillation frequency of the crystal oscillator changes, so that the pressure is detected. Ru. Here, changes in the oscillation frequency due to changes in the air gap between the excitation electrode and the crystal resonator body will be explained with reference to FIGS. 2 and 6.

The electrical equivalent circuit of a crystal resonator is shown in FIG. 2A. The equivalent circuit in a state where the gap with the excitation electrode changes is the second one.
As shown in FIG. B, the oscillation frequency changes as the interelectrode capacitance CO changes as shown in FIG. In other words, since the change in co changes in conjunction with the size of the air gap, the change in external pressure can be interpreted as a change in the oscillation frequency.

When the pressure sensor of the present invention is used to create a pressure side for measuring gas pressure, the configuration is shown in Figure 4, where the oscillation frequency of the standard crystal oscillator 21 and the oscillation frequency of the crystal pressure sensor are compared. The change in the oscillation frequency of the crystal pressure sensor is read and displayed as a gas pressure value.

FIG. 5 shows another embodiment of the present invention, in which the crystal resonator main body 3
The excitation electrode 3f6 is in close contact with the other excitation electrode 63.
α is installed with a gap between it and the crystal oscillator body so that it reacts to external pressure. Figure 6 shows another embodiment of the present invention, which has two pressure spaces into which the measurement gas is introduced. Each pressure space has a quartz crystal oscillator pressure sensor. In this embodiment, a gas whose pressure is not known in advance is introduced into the pressure space 41, and a gas whose pressure is to be measured is introduced into the pressure space 42. At this time, the excitation electrodes 46 and 44 each having a gap are bent in response to the pressure, and the oscillation frequencies of the crystal oscillators are taken out from the electrode leads 45 and 46, respectively, and the oscillation frequencies of both crystal oscillators are compared, and the measurement is performed. You can find out the pressure of the desired gas.

By the way, the crystal resonator body according to the present invention has flat frequency-temperature characteristics. For example, by using an AT cut or GT cut resonator, very accurate measurements can be made without temperature correction. is possible.

As described above, according to the present invention, gas pressure can be detected as a digital value, there is little variation due to power supply voltage, and there is no error in remote measurement. A very high precision pressure sensor can be provided.

[Brief explanation of the drawing]

FIG. 1 is an example of the present invention, FIG. 2 is an equivalent circuit of a crystal resonator and an equivalent circuit of the present invention, FIG. 6 is a diagram showing the relationship between frequency change and air gap amount in the present invention, and FIG. Block diagrams of the system according to the present invention, FIGS. 5 and 6, are diagrams showing other embodiments of the present invention. 11.31.50...Support body 12.32.47.48...Crystal resonator body 1
3ff, 13b, 33a, 36b, 43.44...
...Excitation electrode 14.25, 34, 41.43...Pressure space 1
5.35, 45.46... Electrode lead 21...
...Reference oscillator 22...Crystal oscillator pressure sensor 23...
・Frequency comparison circuit 24...Display section 14fZ, 341Z, 51.52------Gas inlet or more! $1 Figure 0 Figure 3 Figure 2 (β) Figure 4 1 209- Figure 5 Figure 6 4 moves at

Claims (1)

[Claims] 1. The excitation electrode of the crystal resonator is installed separately from the main body of the crystal resonator, and the gap is changed according to the external pressure, and the pressure is increased by changing the oscillation frequency of the crystal resonator according to the gap. Quartz crystal pressure sensor to detect. 2. Two crystal oscillators are attached to the same support, both have an excitation electrode structure with a gap, and a separate system of pressure is introduced to each crystal oscillator, and each gap is adjusted according to the pressure. A crystal pressure sensor that detects pressure by changing the oscillation frequency of each crystal oscillator. 3. In claim 1, the excitation electrodes of the crystal resonator are formed so as to sandwich the crystal resonator main body, and the excitation electrodes on both sides have a gap with the crystal resonator main body, and both react to external pressure. A crystal oscillator pressure sensor characterized by the following. 4. In claim 1, the excitation electrodes of the crystal resonator are formed so as to sandwich the crystal resonator main body, the excitation electrode on one side is formed in close contact with the crystal resonator main body, and the excitation electrode on the other side is formed so as to sandwich the crystal resonator main body. The electrode is formed with a gap between it and the crystal oscillator body.
A quartz crystal oscillator pressure sensor characterized by a structure that responds to external pressure.