JP2010071891A - Optical pressure gauge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost pressure gauge resistant to disturbance. <P>SOLUTION: Light sent out from an LED of a first photo-reflector 22 is projected to a diaphragm 20. The diaphragm 20 bends correspondingly to a pressure it receives to reflect the light. The reflected light from the diaphragm 20 is converted into an electrical signal by a first PT 32 provided for the photo-reflector 22. Meanwhile, light sent out from an LED of a second photo-reflector 23 is projected to a sidewall 21 while reflected light from the sidewall 21 is converted into an electrical signal by a PT of a second photo-reflector 23. When these two electrical signals are sent to an operational amplifier 24, only a signal corresponding to the pressure received by the diaphragm 20 is amplified by differential amplification and output. An analog voltage signal output from the operational amplifier 24 is converted into a digital frequency signal by a V-f converter 25, transmitted to an f-V converter 26 by a transmission line 30, and converted into an analog voltage signal by the f-V converter 26 and output. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical pressure gauge that measures the pressure received by a diaphragm using light.

As an optical pressure gauge, for example, an optical fiber pressure gauge using an optical fiber as shown in Patent Document 1 is known. In this pressure gauge, as shown in FIG. 6, the light beam of the second LED 3 having a wavelength different from that of the first LED (light emitting diode) 2 is guided to the light source optical fiber 5 by the coupler 4 and transmitted to the sensor head 6. In the sensor head 6, a part of the optical fiber cladding of the light source optical fiber 5 and the light receiving optical fiber 11 is removed and fused, whereby a part of the light of the light source optical fiber 5 is attached to the light receiving optical fiber 11. Led. Further, the light projected from the light source optical fiber 5 onto the pressure receiving diaphragm 1 is reflected only by the wavelength of the first LED 2 by the wavelength selective material applied to the inner surface 1 a of the diaphragm, and this reflected light is reflected by the light receiving optical fiber 11. The light is received and integrated with the reference light by the coupling unit 7 and guided to the mirror 12 having wavelength selectivity. The reflected light from the pressure receiving diaphragm 1 is reflected by the mirror 12 and converted into an electric signal by the first PD (photodiode) 15, while the reference light is transmitted through the mirror 12 and converted into an electric signal by the second PD 16. By processing the reflected light signal from the first PD 15 with the reference signal from the second PD 16 by the calculation means 17 such as division, for example, pressure measurement can be performed without being affected by the change in the light amount due to disturbance. Moreover, the output adjustment means 18 which makes the corresponding relationship (for example, linear relationship) of the output signal of the calculating means 17 and a receiving pressure is provided.
Japanese Patent Laid-Open No. 03-243822

  Since the conventional optical fiber pressure gauge uses a light source optical fiber and a light receiving optical fiber, its manufacturing price is as high as 10 times the price of a commercially available pressure gauge. This high price is a problem for the spread of optical fiber pressure gauges.

  Further, in an optical fiber pressure gauge using an optical fiber, the amount of light 1 dB is attenuated by one connector. When there are six connectors, the amount of LED light is approximately 0.25 with respect to the light emitting unit 1 at the position of the PD. Actually, the loss is about 0.2 because of optical loss due to the optical fiber, reflection loss from the diaphragm, and the like. Further, it is difficult to put all of the LED light into the optical fiber. When the LED fiber end output is 30 μW, the PD fiber end input is 6 μW. Since the amount of light is small, the LED and PD elements must be cooled to prevent noise.

  For these reasons, it is desirable to provide an optical pressure gauge that can achieve low cost and can withstand disturbances by suppressing the attenuation of light quantity.

  Therefore, an object of the present invention is to provide an optical pressure gauge that is inexpensive and resistant to disturbances.

  An optical pressure gauge according to an aspect of the present invention includes a diaphragm that bends in response to a received pressure, a first light emitting diode that projects light onto the diaphragm, and converts reflected light from the diaphragm into an electrical signal for output. A first photoreflector having a first phototransistor, a side wall provided adjacent to the diaphragm, a second light emitting diode for projecting light on the side wall, and light reflected from the side wall. A second photoreflector having a second phototransistor that converts the signal into a signal and outputs the differential signal between the electrical signal output from the first photoreflector and the electrical signal output from the second photoreflector. An operational amplifier that amplifies and outputs only a signal corresponding to the pressure received by the diaphragm by amplification, and an analog output from the operational amplifier A V-f converter that converts a pressure signal into a digital frequency signal and outputs it, a transmission line that transmits the digital frequency signal output from the V-f converter, and an analog voltage for the digital frequency signal transmitted by the transmission line And an f-V converter that converts the signal into a signal and outputs the signal.

  According to the present invention, it is possible to provide a pressure gauge that is inexpensive and resistant to disturbance.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing an example of the configuration of the optical pressure gauge according to the first embodiment of the present invention.

  The optical pressure gauge according to the first embodiment includes a diaphragm 20, a side wall 21, a first photo reflector 22, a second photo reflector 23, an operational amplifier 24, a Vf converter 25, an fV converter 26, and a transmission. It has a line 30.

  The diaphragm 20 is a plate that bends corresponding to the pressure received.

  The side wall 21 is a plate provided adjacent to the diaphragm 20 and is disposed so as to surround the first photo reflector 22 and the second photo reflector 23 together with the diaphragm 20. Unlike the diaphragm 20, the side wall 21 does not bend according to the pressure received.

  The first photo reflector 22 and the second photo reflector 23 are parts to which MEMS (Micro Electro Mechanical Systems) technology is applied. As shown in FIG. 2, each of the first photo reflector 22 and the second photo reflector 23 emits light (LED) 31. And a phototransistor (PT) 32 that receives light, converts it into an electrical signal, and outputs it. The external dimension of each photo reflector is, for example, 1.3 mm × 1.6 mm × 0.6 mm.

  Here, for convenience, the LED 31 provided in the first photo reflector 22 is referred to as a “first LED 31”, and the LED 31 provided in the second photo reflector 23 is referred to as a “second LED 31”. Similarly, the phototransistor 32 included in the first photoreflector 22 is referred to as “first PT32”, and the phototransistor 32 included in the second photoreflector 23 is referred to as “second PT32”. To do.

  That is, the first photo reflector 22 includes a first LED 31 that projects light onto the diaphragm 20 and a first PT 32 that converts the reflected light from the diaphragm 20 into an electrical signal and outputs the electrical signal. The second photo reflector 23 includes a second LED 31 that projects light onto the side wall 21 and a second PT 32 that converts the reflected light from the side wall 21 into an electrical signal and outputs the electrical signal.

  The operational amplifier 24 performs differential amplification between the electric signal output from the first PT 32 provided in the first photo reflector 22 and the electric signal output from the second PT 32 provided in the second photo reflector 23. This is a differential amplifier that amplifies and outputs only a signal corresponding to the pressure received by the diaphragm 20.

  The Vf converter 25 is a converter that converts a voltage signal (analog voltage signal) as an analog signal output from the operational amplifier 24 into a frequency signal (digital frequency signal) as a digital signal and outputs the signal.

  The transmission line 30 is a transmission medium that transmits the digital frequency signal output from the Vf converter 25.

  The fV converter 26 is a converter that converts the digital frequency signal transmitted through the transmission line 30 into an analog voltage signal and outputs the analog voltage signal.

  In such a configuration, the light transmitted from the first LED 31 provided in the first photo reflector 22 is projected onto the diaphragm 20. The diaphragm 20 bends corresponding to the pressure received and reflects the light from the LED 31. The amount of deflection of the diaphragm 20 and the amount of reflected light have a linear (proportional) relationship. The reflected light from the diaphragm 20 is converted into an electric signal by the first PT 32 provided in the first photo reflector 22. On the other hand, the light transmitted from the second LED 31 provided in the second photo reflector 23 is projected onto the side wall 21, and the reflected light from the side wall 21 is transmitted by the second PT 32 provided in the second photo reflector 23. It is converted into an electrical signal. When these two electrical signals are sent to the operational amplifier 24, only a signal corresponding to the pressure received by the diaphragm 20 is amplified and output by differential amplification.

  The analog voltage signal output from the operational amplifier 24 is converted into a digital frequency signal by the Vf converter 25 and output. This digital frequency signal is transmitted to the fV converter 26 via the transmission line 30. The digital frequency signal transmitted through the transmission line 30 is converted into an analog voltage signal by the fV converter 26 and output. Thus, an analog voltage signal corresponding to the pressure received by the diaphragm 20 is obtained, and the pressure is measured.

  According to the first embodiment, by applying the MEMS technology, it is possible to configure a photo reflector combining an LED and a PT, and it is possible to reduce the size of the sensor unit, and to cause electromagnetic induction noise during long-distance transmission. If the digital frequency is at a level that is not affected even if a failure occurs, pressure can be measured without fluctuation due to disturbance by converting the signal to an analog voltage in the fV converter. Moreover, since no optical fiber is used, it is possible to reduce the price.

(Second Embodiment)
FIG. 3 is a diagram showing an example of the configuration of an optical pressure gauge according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the component which is common in the above-mentioned 1st Embodiment, and the detailed description is abbreviate | omitted. Below, it demonstrates centering on a different part from the above-mentioned 1st Embodiment.

  In the second embodiment (FIG. 3), instead of the transmission line 30 shown in the first embodiment (FIG. 1), an LED 27, an optical fiber 28, and a photodiode (PD) 29 are provided.

  The LED 27 is an element that converts the digital frequency signal output from the Vf converter 25 into light and transmits the light. For example, the LED 27 blinks light at a frequency indicated by a signal from the Vf converter 25.

  The optical fiber 28 is a transmission medium that transmits light transmitted from the LED 27 to the PD 29, and has a feature that it is not easily affected by electromagnetic induction noise during long-distance transmission.

  The PD 29 is an element that converts the light transmitted through the optical fiber 28 into a digital frequency signal of an electrical signal and outputs it.

  The fV converter 26 described above converts the digital frequency signal transmitted through the optical fiber 28 into an analog voltage signal and outputs the analog voltage signal.

  In such a configuration, when the analog voltage signal output from the operational amplifier 24 is converted into a digital frequency signal by the V-f converter 25, the digital frequency signal is converted into light by the LED 27 and transmitted. Light transmitted from the LED 27 is transmitted to the PD 29 through the optical fiber 28. The light transmitted through the optical fiber 28 is converted into an electric digital frequency signal by the PD 29 and output. This digital frequency signal is converted into an analog voltage signal by the f-V converter 26 and output. Thus, an analog voltage signal corresponding to the pressure received by the diaphragm 20 is obtained, and the pressure is measured.

  According to the second embodiment, the same effects as those of the first embodiment can be obtained, and since an optical fiber is used, it is not affected by electromagnetic induction noise during long-distance transmission. The effect that pressure measurement can be performed without fluctuation due to disturbance is obtained. Further, since the amount of optical fiber is smaller than that of a conventional optical pressure gauge, it is possible to reduce the price.

(Third embodiment)
FIG. 4 is a diagram showing an example of the configuration of an optical pressure gauge according to the third embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the component which is common in the above-mentioned 1st Embodiment, and the detailed description is abbreviate | omitted. Below, it demonstrates centering on a different part from the above-mentioned 1st Embodiment.

  In the third embodiment (FIG. 4), a first laser diode (LD) is used in place of the first photo reflector 22 and the second photo reflector 23 shown in the first embodiment (FIG. 1). 41 and a second laser diode (LD) 42 are provided.

  The first laser diode 41 is an element that projects light onto the diaphragm 10, and includes a first photodiode (first PD) that converts the reflected light from the diaphragm 10 into an electrical signal and outputs it. Yes.

  The second laser diode 42 is an element that projects light onto the side wall 21, and includes a second photodiode (second PD) that converts the reflected light from the side wall 21 into an electrical signal and outputs it. Yes.

  In such a configuration, the light transmitted from the first laser diode 41 is projected onto the diaphragm 20. The diaphragm 20 bends corresponding to the pressure received and reflects the light from the first laser diode 41. The amount of deflection of the diaphragm 20 and the amount of reflected light have a linear (proportional) relationship. The reflected light from the diaphragm 20 is converted into an electric signal by the first PD provided in the first laser diode 41. On the other hand, the light transmitted from the second laser diode 42 is projected onto the side wall 21, and the reflected light from the side wall 21 is converted into an electric signal by the second PD provided in the second laser diode 42. When these two electrical signals are sent to the operational amplifier 24, only a signal corresponding to the pressure received by the diaphragm 20 is amplified and output by differential amplification.

  The analog voltage signal output from the operational amplifier 24 is converted into a digital frequency signal by the Vf converter 25 and output. This digital frequency signal is transmitted to the fV converter 26 via the transmission line 30. The digital frequency signal transmitted through the transmission line 30 is converted into an analog voltage signal by the fV converter 26 and output. Thus, an analog voltage signal corresponding to the pressure received by the diaphragm 20 is obtained, and the pressure is measured.

  According to the second embodiment, even when a laser diode is used for the sensor unit, the same effect as that of the first embodiment can be obtained.

(Fourth embodiment)
FIG. 5 is a diagram showing an example of the configuration of an optical pressure gauge according to the fourth embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the component which is common in the above-mentioned 1st-3rd embodiment, and the detailed description is abbreviate | omitted. In the following, a description will be given centering on differences from the third embodiment described above.

  In the fourth embodiment (FIG. 5), instead of the transmission path 30 shown in the third embodiment (FIG. 4), an LED 27, an optical fiber 28, and a photodiode (PD) 29 are provided. These elements 27 to 29 are the same as those described in the second embodiment (FIG. 3).

  In such a configuration, when the analog voltage signal output from the operational amplifier 24 is converted into a digital frequency signal by the V-f converter 25, the digital frequency signal is converted into light by the LED 27 and transmitted. Light transmitted from the LED 27 is transmitted to the PD 29 through the optical fiber 28. The light transmitted through the optical fiber 28 is converted into an electric digital frequency signal by the PD 29 and output. This digital frequency signal is converted into an analog voltage signal by the f-V converter 26 and output. Thus, an analog voltage signal corresponding to the pressure received by the diaphragm 20 is obtained, and the pressure is measured.

  According to the fourth embodiment, the same effects as those of the third embodiment described above can be obtained, and since an optical fiber is used, there is no influence of electromagnetic induction noise during long-distance transmission. The effect that pressure measurement can be performed without fluctuation due to disturbance is obtained. Further, since the amount of optical fiber is smaller than that of a conventional optical pressure gauge, it is possible to reduce the price.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The figure which shows an example of a structure of the optical pressure gauge which concerns on the 1st Embodiment of this invention. The figure which shows an example of a structure of a photo reflector. The figure which shows an example of a structure of the optical pressure gauge which concerns on the 2nd Embodiment of this invention. The figure which shows an example of a structure of the optical pressure gauge which concerns on the 3rd Embodiment of this invention. The figure which shows an example of a structure of the optical pressure gauge which concerns on the 4th Embodiment of this invention. The figure which shows an example of a structure of the conventional optical fiber pressure gauge.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 20 ... Diaphragm, 21 ... Side wall, 22 ... 1st photo reflector, 23 ... 2nd photo reflector, 24 ... Operational amplifier, 25 ... Vf converter, 26 ... fV converter, 27 ... Light emitting diode (LED), 28 ... Optical fiber, 29 ... Photodiode (PD), 30 ... Transmission line, 31 ... Light emitting diode (LED), 32 ... Phototransistor (PT), 41 ... First laser diode (LD), 42 ... Second Laser diode (LD).

Claims (4)

A diaphragm that bends in response to the pressure received,
A first photoreflector having a first light emitting diode that projects light onto the diaphragm, and a first phototransistor that converts reflected light from the diaphragm into an electrical signal and outputs the electrical signal;
A side wall provided adjacent to the diaphragm;
A second photoreflector having a second light emitting diode that projects light on the side wall, and a second phototransistor that converts reflected light from the side wall into an electrical signal and outputs the electrical signal;
An operational amplifier that amplifies and outputs only the signal corresponding to the pressure received by the diaphragm by differential amplification of the electrical signal output from the first photoreflector and the electrical signal output from the second photoreflector;
A Vf converter that converts an analog voltage signal output from the operational amplifier into a digital frequency signal and outputs the digital frequency signal;
A transmission line for transmitting a digital frequency signal output from the Vf converter;
An optical pressure gauge comprising: an fV converter that converts a digital frequency signal transmitted through the transmission line into an analog voltage signal and outputs the analog voltage signal. A diaphragm that bends in response to the pressure received,
A first photoreflector having a first light emitting diode that projects light onto the diaphragm, and a first phototransistor that converts reflected light from the diaphragm into an electrical signal and outputs the electrical signal;
A side wall provided adjacent to the diaphragm;
A second photoreflector having a second light emitting diode that projects light on the side wall, and a second phototransistor that converts reflected light from the side wall into an electrical signal and outputs the electrical signal;
An operational amplifier that amplifies and outputs only the signal corresponding to the pressure received by the diaphragm by differential amplification of the electrical signal output from the first photoreflector and the electrical signal output from the second photoreflector;
A Vf converter that converts an analog voltage signal output from the operational amplifier into a digital frequency signal and outputs the digital frequency signal;
A third light emitting diode that converts the digital frequency signal output from the Vf converter into light and transmits the light;
An optical fiber for transmitting light transmitted from the third light emitting diode;
A photodiode that converts the light transmitted by the optical fiber into a digital frequency signal of an electrical signal and outputs it;
An optical pressure gauge comprising: an fV converter that converts a digital frequency signal output from the photodiode into an analog voltage signal and outputs the analog voltage signal. A diaphragm that bends in response to the pressure received,
A first laser diode that projects light onto the diaphragm, and includes a first photodiode that converts the reflected light from the diaphragm into an electrical signal and outputs the electrical signal;
A side wall provided adjacent to the diaphragm;
A second laser diode that projects light onto the side wall, the second laser diode including a second photodiode that converts the reflected light from the side wall into an electrical signal and outputs the electrical signal;
An operational amplifier that amplifies and outputs only the signal corresponding to the pressure received by the diaphragm by differential amplification of the electrical signal output from the first laser diode and the electrical signal output from the second laser diode;
A Vf converter that converts an analog voltage signal output from the operational amplifier into a digital frequency signal and outputs the digital frequency signal;
A transmission line for transmitting a digital frequency signal output from the Vf converter;
An optical pressure gauge comprising: an fV converter that converts a digital frequency signal transmitted through the transmission line into an analog voltage signal and outputs the analog voltage signal. A diaphragm that bends in response to the pressure received,
A first laser diode that projects light onto the diaphragm, and includes a first photodiode that converts the reflected light from the diaphragm into an electrical signal and outputs the electrical signal;
A side wall provided adjacent to the diaphragm;
A second laser diode that projects light onto the side wall, the second laser diode including a second photodiode that converts the reflected light from the side wall into an electrical signal and outputs the electrical signal;
An operational amplifier that amplifies and outputs only the signal corresponding to the pressure received by the diaphragm by differential amplification of the electrical signal output from the first laser diode and the electrical signal output from the second laser diode;
A Vf converter that converts an analog voltage signal output from the operational amplifier into a digital frequency signal and outputs the digital frequency signal;
A third light emitting diode that converts the digital frequency signal output from the Vf converter into light and transmits the light;
An optical fiber for transmitting light transmitted from the third light emitting diode;
A third photodiode that converts the light transmitted by the optical fiber into a digital frequency signal of an electrical signal and outputs the signal;
An optical pressure gauge comprising: an fV converter that converts a digital frequency signal output from the third photodiode into an analog voltage signal and outputs the analog voltage signal.

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