JPS5856820B2 - Shinkuudosekutei Souchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure transducer for a vacuum system.

The purpose of the present invention is to use a tuning fork type crystal oscillator in a pressure transducer of a vacuum device, and to improve the accuracy of vacuum level measurement by utilizing its oscillation frequency versus vacuum level characteristics and the stability of the oscillation frequency. It is.

The conventional method of measuring the degree of vacuum involves discharging the air using a Keisler tube.
There are methods to measure it by the length of the Glucks dark part, methods to measure it with a Virani vacuum gauge, and methods to measure it with an ionization vacuum gauge.

However, in either case, the area that can be covered is narrow, and it is necessary to replace the vacuum device at each vacuum level.

Below 10 torr for Geissler tube, below 1.0 for for Pirani vacuum gauge, 10 tor for ionization vacuum gauge
When trying to measure up to 1o-4for, for example, more than r, the degree of vacuum at each stage could not be measured unless two or more vacuum devices were placed side by side.

In addition, its measurement accuracy was low, making it an unsatisfactory measuring instrument when high-precision measurement is required these days.

In addition, a pressure measuring device using a pressure sensor as a vibrator is proposed in Japanese Patent Publication No. 49-1234, but the vibrators conventionally used are high frequency vibrators such as AT or GT, and these vibrations Even when oscillating in the atmosphere, there is almost no variation in frequency, making it impossible to apply the degree-of-vacuum measuring device to which the present invention is directed.

The present invention eliminates such drawbacks and changes the tor to 10 tor.
A wide area up to the tor can be covered with one vacuum device and one pressure transducer, and the measurement accuracy can be very high because it uses changes in the oscillation frequency of a crystal resonator.

The present invention will be explained below with reference to the drawings.

FIG. 1 is an external view of a tuning fork type crystal resonator used as a pressure transducer in the present invention.

1 is a tuning fork-shaped crystal resonator formed by photo-etching; 2 and 3 are electrodes; an electrode along the periphery of at least one of the forks and an electrode along the center of the fork, forming a pair of electrodes; As is clear from the figure, the electrodes are arranged such that the electrode along the periphery of one prong becomes the electrode along the center of the other prong, forming two terminals.

By applying an electric field to the vibrator described above, each prong vibrates in opposite directions parallel to the plane on which the electrodes are provided.

4 and 5 are punch ink lines, 6 is a vibrator fixing base, and t is the thickness of a crystal thin plate, which is less than 200 μm, and is not directly related to the oscillation frequency of this vibrator.

Figure 2 shows the vacuum 1p (
tor) and the amount of frequency change.

As shown in FIG. 2, the oscillation frequency generally decreases as the degree of vacuum increases.

This is mainly caused by the amplitude characteristics of the vibrator.

In addition, the amplitude % is closely related to the thickness t of the vibrator, and as shown in curves 7゜8.9 and 10 in Figure 2, as t becomes smaller, the frequency change △f increases with respect to the vacuum change △p. growing.

That is, when the vibrator is made thinner, Δf/Δp becomes larger, and measurement sensitivity increases.

Furthermore, in a high vacuum, the oscillation frequency is saturated and shows a constant value, so the frequency f at this time.

If the relationship between the amount of frequency change △f and the degree of vacuum p is found based on △f, then p can be found from △f.

Also, in order to increase measurement sensitivity, the transducer should be made thinner.
It is better to increase △f/△p.

For this reason, it may be necessary to make an ultra-thin resonator, but recent improvements in photo-etching technology and polishing technology have made it possible to make ultra-thin resonators with a thickness of 25 μm.
It has become possible to create ultra-thin oscillators called t.

Using such a vibrator, it is possible to use a oscillator of 10 or more tors to 10 f.
Since the frequency changes by more than 2.5 x 10'' over a wide range up to or, the degree of vacuum can be measured with very high accuracy.

FIG. 3 is an example of a vacuum degree measuring device according to the present invention.

1 is an ultra-thin tuning fork type crystal resonator of 200μ or less as shown in Fig. 1, 4 and 5 are honting wires, 6 is a fixed stand, 11 is a probe containing the resonator, 12 is an oscillation circuit, △f The main body includes a comparison circuit for determining Δf, a circuit for converting Δf into the degree of vacuum p, and a display section.

The degree of vacuum in the measurement container can be easily determined by placing this probe in a measurement container, causing the crystal oscillator to oscillate, and checking the oscillation frequency.

The system of the vacuum degree measuring device according to the present invention is schematically shown in a block diagram in FIG.

Reference frequency f stored in memory 14.

and the oscillation circuit 13 of the tuning fork crystal resonator 1 which becomes the sensor.
The comparator circuit 15 compares the outputs f, and the beat circuit 16 obtains a frequency difference Δfo.

The conversion circuit 17 is △f. This is a circuit for converting pressure values, and its output is displayed by a commonly used decoder 18 and display 19, so that the pressure value can be seen at a glance.

According to the present invention, focusing on the fact that a tuning fork type crystal resonator with a thickness of 200 μm or less changes continuously according to the atmospheric pressure, the frequency of the tuning fork type crystal resonator exposed to the atmosphere of a vacuum container changes. The amount of change is measured using a comparison circuit, and the output is passed through a conversion circuit to convert the magnitude of the frequency aim △f and the pressure value, and finally the degree of vacuum can be determined at a glance using the decoder display. This configuration has the following effects.

a) Since a tuning fork type crystal oscillator with a thickness of 200 μm or less is used as the sensor, and the difference in frequency plane is fixed as the degree of vacuum, a very compact and highly accurate degree of vacuum measuring device can be provided.

This is because a tuning fork type crystal resonator vibrates in a bending mode, so it is extremely sensitive to the influence of atmospheric pressure and generates large frequency fluctuations, making it ideal as a sensor. Because the type crystal resonator has symmetry, stable vibration can be obtained even if the resonator is made smaller.

b) Also, since the frequency difference is used as the measured quantity,
All of the detection and display circuits can be constructed from simple digital circuits, making it possible to provide an inexpensive and highly accurate degree of vacuum measuring device.

C) Furthermore, since the tuning fork type crystal oscillator is fixed to a probe that is detachably attached to the vacuum vessel, it is easy to adjust the thickness of the crystal oscillator to the optimum thickness depending on the range of vacuum + constant vacuum. Has the advantage of being replaced.

[Brief explanation of the drawing]

Figure 1 shows a tuning fork crystal resonator with a thickness of t. FIG. 2 shows the relationship between the degree of vacuum p of the crystal resonator and the periodic change ΔT. FIG. 3 shows a vacuum degree measuring device constructed according to the present invention. FIG. 4 is a block diagram of the vacuum degree measuring device system according to the present invention. 1... Tuning fork type crystal oscillator, 2, 3...
Electrode, 4゜5...Honting wire, 6...
... Vibrator fixing table, 7... p-△f/f curve of a vibrator with a plate thickness of 200μ, 8... p-△f/f curve of a vibrator with a plate thickness of 100μ , 9...Plate thickness 50μ
p-△f/f curve of the resonator, 10...Plate thickness 2
p-Δf/f curve of a 5μ vibrator, 11... Probe, 12... Vacuum degree measuring device main body.

Claims (1)

[Scope of Claims] 1. A tuning fork type crystal resonator made of a thin crystal plate with a thickness of 200 μm or less is used as a pressure quadrangle juicer in a vacuum container,
and a reference frequency f. and means for detecting oscillation frequency overlap, including a comparison circuit for comparing the measured frequency f of the tuning fork type crystal resonator, and a conversion circuit for setting a stress value according to the detection result. A base of the tuning fork crystal resonator is fixed to a fixing base provided in a glove which is connected to the vacuum container and is detachable from the vacuum container, and the tuning fork crystal resonator is attached to the vacuum container. A degree of vacuum measuring device characterized in that it is arranged so as to be exposed in an atmosphere of