JPS60149937A - Pressure measuring apparatus - Google Patents

Abstract

PURPOSE:To achieve a highly accurate measurement of the S/N ratio with a simple construction by employing a linear array of numerous ON-OFF type light receiving elements as a photo detector. CONSTITUTION:A fine light beam 14 from a light source 11 is introduced to the surface of an area plate 10b at an angle theta from a slant direction with a light transmission path 13. The reflect light is received with a photo detector 12 to be converted to an electrical signal. The photo detector 12 is made up of a photo diode array in which numerous ON-OFF type light receiving elements 12a-12n are arranged linearly and placed in the direction of receiving the reflected light 18 from the area plate 10b in such a manner as to be orthogonal to the reflected light 18.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pressure measuring device that converts the amount of mechanical displacement of a pressure-sensitive element due to a pressure change into an electrical signal using an optical signal.

[Prior art]

Conventionally, pressure changes have been detected by detecting the deflection of a silicon diaphragm using changes in piezoresistance, and by detecting the deflection of a metal diaphragm using changes in capacitance. However, since all of these detection methods are electronic and directly extract electrical signals, they are vulnerable to electromagnetic induction, which can cause blemishes due to weak signals when considering explosion protection.

Therefore, it was necessary to ensure system safety by using barriers, etc.

Therefore, recently, various displacement conversion devices have been proposed that convert mechanical displacement amounts into electrical signals using optical signals.

As shown in Figure 1, this transfers light from a light source 1 to an optical transmission line 2.
The light is guided to the diaphragm 3 for reflection, and the displacement d when the diaphragm 3 receives pressure P is used as a change in the amount of reflected light by the receiver 4 and converted into an electrical signal. Moreover, it has the great advantage of being excellent in explosion-proof properties.

In this case, semiconductor light sources and semiconductor photodetectors generally fluctuate slightly due to fluctuations in ambient temperature, power supply, and other influences, so they lack stability and cannot be expected to provide favorable performance. Therefore, as shown in FIG. 2, two light receivers 4A are used to measure the displacement dl and dl on both sides of the diaphragm 3.

By detecting 4B and calculating dl dl, noise caused by multiple temperature changes, power fluctuations, etc. can be canceled out, and performance has been improved. It is known that the intensity of the light source is controlled so that the sum signal of the signals from two sets of light receivers that detect dl and d is constant.

However, in all of these systems, the electrical signal from the photoreceiver is analog, so the signal-to-noise ratio (S/N) remains unsatisfactory.

[Summary of the invention]

The present invention has been made in view of the above-mentioned points, and uses an extremely simple structure in which a one-dimensional array of a large number of on-off type light receiving elements is used as a light receiver, and mechanical displacement is converted into a digital signal. The S/N is improved by overcoming the inherent instability of semiconductor light sources and receivers.
The present invention provides a pressure measuring device that enables highly accurate measurement with a high ratio.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

〔Example〕

FIG. 3 is a configuration diagram showing an embodiment of the present invention.

In the figure, 10 is a pressure sensitive element, 11 is a semiconductor light source, and 12 is a pressure sensitive element.
is a light receiver, and the pressure sensitive element 10 is a metal diamond slam 1 having a fixed peripheral edge and a rigid area plate 10b in the center.
0a, and the surface of the area plate 10b is finished to a mirror surface.

In this case, the pressure sensitive element 16 is not limited to a diaphragm, and for example, as shown in FIG.
The bellows 16 is formed of a silicon diaphragm 15 having an integral diameter of 5 m, and the surface of the thick wall portion 15a is mirror-finished, or a rigid area plate 17 is attached to the opening at one end of the bellows 16 as shown in FIG. The surface of the area plate 17 may be mirror-finished. In short, any pressure-sensitive element may be used as long as it has a movable part that displaces in parallel when pressure is applied, and the movable part is provided with a mirror surface part that effectively reflects light.

A thin original beam 14 from the light source 11 is guided obliquely to the surface of the area plate 10b at a certain angle θ by the original transmission line 13, and irradiates the surface. The reflected light 18 is then received by the light receiver 12 and converted into an electrical signal.

Here, the light receiver 12 that characterizes the present invention includes a large number of on/off type light receiving elements 12a, 12b, 12c...
It is constituted by a photodiode array in which 12n of . And each on-off type light receiving element 12a,
12b, 12c, . . . , 12n are sequentially operated by a shift register (not shown), and are configured to output an on signal when receiving light and an off signal when not receiving light.

Now, suppose that the area plate 10b is displaced in parallel by an amount d as shown by the broken line in FIG.
dnθ). On the other hand, when the light receiver 12 is tilted by the bending angle ψ with respect to the reflected light 18 as shown in FIG. 6, the amount of movement (distance) f of the reflected light 18a on the light receiver 12 becomes.

Therefore, by substituting e=2ds(nθ into the above equation (1), it becomes 2dslnθ f=庖ψ.

Here, if θ=ψ=70°, f=5.5d Also, if θ−ψ=800, f=11.3d becomes.

That is, the amount of displacement d of the area plate 10b on the light receiver 12 is expanded by about 5 to 11 times.

The recent photodiode array consisting of on/off light receiving elements constituting the light receiver 12 has a light sensor pitch of 1.
Since the number of elements reaches more than 500 at around 0 μm, the small displacement (μ order) of the light receiving element due to the change in p of the light sensor that is receiving light (turning on) can be detected with a good S/N ratio. It can be detected by

In other words, in conventional light receivers, the amount of reflected light received by the light receiver changes depending on the amount of displacement of the pressure-sensitive element, so when it decreases, it is easily affected by noise. 7 When reflected light is detected using an Otodiode array, the intensity of the pulse signal from each party sensor is almost constant and does not change greatly depending on the amount of displacement of the pressure-sensitive element, so it is less susceptible to the influence of noise. It is possible to improve the S ratio.

FIG. 7 is a side view of essential parts showing another embodiment of the present invention.

In this embodiment, separately manufactured mirrors 25 are attached to the surface of the area plate 10b at appropriate angles. According to such a configuration, the optical axis direction of the light source, the light source and the light receiver 1
It has the advantage that the arrangement position R of 2 can be changed freely.

Incidentally, in each of the above embodiments, the case where the pressure P is applied to one side of the pressure sensitive element 10 has been explained, but the present invention is not limited to this. Of course, it is also possible to do so.

〔Effect of the invention〕

As explained above, in the pressure measuring device according to the present invention, a movable part of a pressure sensitive element is provided with a mirror surface part, the mirror surface part is irradiated with a source from an oblique direction, and the reflected light is sent to the primary light receiving element of a large number of on/off type. Since the configuration is configured to digitally detect a photodetector consisting of an originally arranged array, minute mechanical displacements of the movable part can be detected with a higher signal-to-noise ratio than conventional analog detection. It is possible to improve measurement accuracy.

[Brief explanation of drawings]

Figures 1 and 2 are block diagrams of a device that converts mechanical displacement into electrical signals using conventional optical signals, respectively.
The figure is a configuration diagram showing one embodiment of the present invention, Fig. 4 (, ),
(b) is a diagram showing another embodiment of the pressure sensitive element, FIGS. 5 and 6 are diagrams showing the relationship between displacement of the area plate and movement of reflected light, and FIG. 7 is a diagram showing another embodiment of the present invention. 01011: Pressure sensitive element, 10a: diaphragm, 10b: area plate, 11: light source, 12@: light receiver, 14: -・Light beam, 1B・
...Reflected light, 25... (2. Patent applicant Yamani) / Newel Co., Ltd. agent Masaki Yamakawa (and 2 others) Figure 4 (a) (b) Figure 6 R Figure 5 4 Figure 7

Claims (1)

[Claims] A mirror surface part is provided in the movable part of the pressure sensitive element, light from a light source is guided obliquely to the mirror surface part and reflected by the mirror surface part, and the reflected light is reflected in an array formed by one-dimensionally arranging a large number of on/off type light receiving elements. 1. A pressure measuring device characterized in that it receives light.