JPS63308531A - Optical type gas pressure sensor - Google Patents

Abstract

PURPOSE:To enable accurate measurement of a gas pressure eliminating explosion-proof processing while being free from effect of turbulence or the like, by determining an attenuation factor of measuring light when the measuring light and reference light passes at a gas pressure measuring point. CONSTITUTION:When driving is started with the energization from power sources 5A and 5B, measuring light 2A from a laser diode 2 and reference light 3A from a laser diode 3 are propagated separately to a optical switch 6, which branches the measuring light 2A and the reference light 3A to be transmitted alternately. The light thus branched is propagated 9 to a gas cell 1. Here, the branched light is transmitted through a lens 10 to be made parallel and passes through a methane gas of the gas cell 1 while the measuring light 2A along is subjected to absorption. After being transmitted through the gas cell 1, light is condensed 11, propagated 12 and received 15 through a light adaptor 13. The light received and propagated is converted 15 to electricity and an electrical signal V corresponding to the measuring light subjected to absorption by a methane gas and an electrical signal VO corresponding to the reference light are outputted. Then, a gas pressure is computed 16 in the basic of a ratio of the electrical signals V and VO.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a gas pressure sensor for optically measuring gas pressure within a gas cell, for example.

(Prior art) Conventionally, as means for measuring gas pressure, semicircular C-type,
The tube is formed into a spiral or helical shape, and based on the displacement of the tip of the tube that occurs when gas pressure is applied inside the tube,
A Bourdon tube pressure sensor is used to mechanically measure gas pressure, and a diaphragm electrode that is displaced by the applied gas pressure () is used to measure gas pressure based on the capacitance that changes in response to the displacement of this diaphragm electrode. A capacitance pressure sensor is used to measure the amount of gas, and a silicon diaphragm that deforms due to applied gas pressure is formed as a strain gauge, and the change in electrical resistance caused by the deformation of this strain gauge is measured using an electric current from a pre-formed bridge circuit. There have been semiconductor pressure sensors and the like that measure gas pressure by taking out a signal.

(Problems to be Solved by the Invention) Among the conventional gas pressure sensors mentioned above, the Bourdon tube pressure sensor is a so-called mechanical gas pressure measuring means, and when gas pressure is measured by this means, the gas pressure is constant. Even so, there was a problem in accurately measuring the gas pressure because the displacement m of the tip of the tube differed depending on the ambient temperature.

In addition, when measuring gas pressure using a capacitive pressure sensor or a semiconductor pressure sensor, it is necessary to directly connect the
Since an electric circuit is connected, there is a problem in that the pressure sensor must be explosion-proofed when measuring the pressure of explosive or flammable gas.

Therefore, there has been a demand for a sensor that optically measures the gas pressure horn as a gas pressure sensor that solves the above problems.The present invention aims to solve the above problem by providing the above-mentioned optical gas pressure sensor, which has not been available in the past. This is a technical issue that should be addressed.

(Means for solving the problem) The technical means for solving the above problem is to use a reference light of a wavelength that is not absorbed by the pressure measurement gas, and a reference light that is absorbed by the gas with an absorption rate corresponding to the pressure of the gas. The reference light and measurement light with a wavelength corresponding to the reference light are alternately projected onto the gas pressure measurement point at a constant output, and each of the reference light and measurement light transmitted through the gas pressure measurement point is converted into an electrical signal, and then the electrical signal corresponding to the reference light and measurement light are converted. An optical gas pressure sensor that calculates a ratio of electrical signals corresponding to optical signals and measures and displays the gas pressure at the gas pressure measurement point based on the ratio, a reference light emitting means that emits the reference light, and the measurement light a measuring light emitting means for emitting light; a switching means for inputting the reference light and the measuring light and alternately transmitting the reference light and the measuring light at arbitrary time-sharing timing; and light transmitting from the switching means. a first optical transmission means for propagating the two light beams transmitted to the gas pressure measurement point;
a second light transmission means for condensing and transmitting both the lights propagated to the gas pressure measurement point by the light transmission means and transmitted through the gas pressure measurement point; A photoelectric conversion means receives and photoelectrically converts both the lights transmitted by the transmission means, and an electric signal corresponding to the reference light and an electric signal corresponding to the measurement light outputted from the photoelectric conversion means are inputted to produce a reference light. a calculation means for calculating the gas pressure at the gas pressure measurement point based on the calculated ratio after calculating the ratio of the corresponding electric signal and the electric signal corresponding to the measurement light; and displaying the gas pressure calculated by the calculation means. The purpose of the present invention is to provide a configuration including a display means for displaying information.

(Function) According to the optical gas pressure sensor having the above configuration, the reference light emitting means emits reference light having a wavelength that is not absorbed by the gas to be measured, while the measurement light emitting means emits reference light at the gas pressure measurement location. When measurement light of a wavelength that is absorbed by the gas with an absorption rate corresponding to the pressure of the gas is emitted, the switching means inputs the reference light and measurement light and divides the reference light and measurement light into predetermined time divisions. The light is separated at the appropriate timing and the reference light and measurement light are sent alternately. The reference light and measurement light alternately transmitted by the switching means are propagated to the gas pressure measurement point by the first light transmission means, and are transmitted through the gas at the gas pressure measurement point. The two lights that have passed through the gas pressure measurement point are collected by the second light transmission means and transmitted to the photoelectric conversion means. The photoelectric conversion means receives the two lights transmitted by the second optical transmission means, converts them into electrical signals, and outputs an electrical signal corresponding to the reference light and an electrical signal corresponding to the measurement light to the calculation means. The calculation means calculates the ratio of the two electrical signals, and further calculates the gas pressure at the gas pressure measurement location based on the calculated ratio.

The gas pressure calculated by the calculation means is converted into an electric signal for display and output to the display means.

The display means inputs an electric signal for display and displays the gas pressure value.

(Example) Next, one embodiment of the present invention will be described with reference to the drawings.

As shown in the figure, the optical gas pressure sensor of this embodiment has methane (CH4
) It measures the pressure of gas. In order to optically measure the methane gas, a radar diode 2 emits measurement light with a wavelength of 1.3μ11 (micrometer) band, and a laser diode emits reference light whose wavelength is in a region not absorbed by methane gas. 3 is provided. In order to supply current for light emission to each of the laser diode 2 and laser diode 3, electric currents gi5A and 5B are connected to the laser diodes 2 and 3, respectively.

Further, an optical switch 6 is provided which receives the constant output measurement light 2A and reference light 3A emitted from the laser diodes 2 and 3, and alternately sends the measurement light 2A and reference light 3A at time-sharing timing. An optical fiber 7 is provided between the laser diode 2 and the optical switch 6 to propagate measurement light 2A emitted from the laser diode 2 to the optical switch 6.

Further, between the laser diode 3 and the optical switch 6, in order to propagate the reference light 3A emitted from the laser diode 3 to the optical switch 6, an optical fiber 8A and an optical attenuator 8 are provided to attenuate and adjust the amount of light passing through. Further, an optical fiber 8B is provided.

The optical switch 6 is connected to the gas cell 1 via an optical fiber 9, and the optical fiber 9 propagates the serial demultiplexed light sent from the optical switch 6 to the gas cell 1.

A lens 10 is installed on the light input side of the gas cell 1 to transmit the demultiplexed light from the end of the optical fiber 9 and make it into a parallel beam. A lens 11 that condenses the separated light in the form of parallel rays.
is provided. The light focused by the lens 11 has a wavelength of 1.3μ corresponding to the pressure of methane gas in the gas cell 1.
Only the m-band measurement light 2A is absorbed, and this focused light is propagated by the optical fiber 12 connected to the light output side of the gas cell 1. Therefore, the propagated light propagated through the optical fiber 12 has a waveform in which the wave height of the measurement light 2A is lower than the wave height of the reference light 3A. The propagated light propagated by the optical fiber 12 is transmitted to a photodiode (PD) 15 via an optical adapter 13 and an optical fiber 14, and is received. The propagating light received by the photodiode 15'C'' is photoelectrically converted by the photodiode 15 and output as an electric signal V corresponding to the measurement light 2A and an electric signal VO corresponding to the reference light 3Δ. , an arithmetic circuit 16 is connected which calculates the gas pressure by inputting the electric signals V and VO outputted from the photodiode 15.The arithmetic circuit 16 displays the gas pressure value calculated by the arithmetic circuit 16. A display device 17 is connected.

Next, the operation of the optical gas pressure sensor for measuring the pressure of methane gas in the gas cell 1 with the above configuration will be explained.

When driving current is applied to the laser diode 2 and the laser diode 3 from the power supplies 5A and 5B,
A measurement light 2A is emitted from the laser diode 2, and a reference light 3A is emitted from the laser diode 3, each with a constant output light amount. The measurement light 2A emitted from the laser diode 2 is propagated to the optical switch 6 by the optical fiber 7, and
Reference light 3A emitted from laser diode 3 is propagated to optical switch 6 via optical fiber 8A, optical attenuator 8, and optical fiber 8B. The optical switch 6 receives the measurement light 2A and the reference light 3A, and splits the measurement light 2A and the reference light 3A into the measurement light 2A and the reference light 3A in accordance with the time division timing and sends them alternately. The demultiplexed light transmitted from the optical switch 6 is propagated to the gas cell 1 through the optical fiber 9, and is input into the gas cell 1. When the demultiplexed light enters the gas cell 1, the demultiplexed light enters the lens 1.
0 and become parallel rays. The parallel beam of demultiplexed light passes through the methane gas in the gas cell 1, and during the transmission process, only the measurement light 2A is absorbed in response to the gas pressure of the methane gas. The light after passing through the gas cell 1 is collected by a lens 11, propagated by an optical fiber 12, and received by a photodiode 15 via an optical adapter 13.

The photodiode 15 receives and photoelectrically converts the propagating light, and outputs an electrical signal V corresponding to the measurement light absorbed by methane gas and an electrical signal VO corresponding to the reference light. Both electric signals (1) and VO are input to an arithmetic circuit 16, and the gas pressure is calculated in the arithmetic circuit 16 based on the ratio of the two electric signals V and VO.

When the gas pressure is calculated by the calculation circuit 16, the gas pressure is converted into an electric signal and output to the display 17. When the electric signal corresponding to the gas pressure is inputted to the display 17, the gas pressure is displayed numerically.

In the above embodiment, the gas pressure measurement point is the gas cell 1, but the gas pressure can be similarly measured by using the leading waveguide instead of the moss of the gas cell 1 as the gas pressure measurement point.

(Effects of the Invention) As described above, in the present invention, measurement is performed when measurement light having a wavelength that is absorbed by the gas to be measured and reference light having a wavelength that is not absorbed by the gas to be measured are passed through a gas pressure measurement point. An optical gas pressure sensor that measures gas pressure optically based on the attenuation rate of light, so there is no need for explosion-proof treatment when measuring gas pressure, and it accurately measures gas pressure without being affected by external disturbances. It has the effect of being able to provide

[Brief explanation of drawings]

The figure is an optical gas pressure measurement system diagram showing an embodiment of the present invention. 1... Gas cell 2... Laser diode 2A... Measurement Light 3... Laser diode 5A, 5B... Power supply 6... Optical switch 7... Optical fiber 8... Optical attenuation Devices 8A, 8B...Optical fiber 9...Optical fiber 13...Optical adapter 14...Optical fiber 15...Photodiode 16...Arithmetic circuit 17...Indicator

Claims (1)

[Claims] A reference light with a wavelength that is not absorbed by the gas whose pressure is being measured and a measurement light with a wavelength that is absorbed by the gas with an absorption rate corresponding to the pressure of the gas are alternately projected onto the gas pressure measurement point at a constant output. Then, each of the reference light and measurement light transmitted through the gas pressure measurement point is converted into an electrical signal, the ratio of the electrical signal corresponding to the reference light and the electrical signal corresponding to the measurement light is calculated, and the gas pressure is measured based on the ratio. An optical gas pressure sensor that measures and displays the pressure of gas at a location, the sensor comprising a reference light emitting means for emitting the reference light, a measurement light emitting means for emitting the measurement light, and a combination of the reference light and the measurement light. a switching means for receiving the light and transmitting the same reference light and measurement light alternately at arbitrary time division timing; and a first for transmitting both the lights transmitted from the switching means to the gas pressure measurement point. an optical transmission means, and a second optical transmission for condensing and transmitting both the lights after the two lights propagated to the gas pressure measurement point by the first light transmission means pass through the gas pressure measurement point. means, photoelectric conversion means for receiving and photoelectrically converting both the lights transmitted by the second optical transmission means, and an electric signal corresponding to the reference light and an electric signal corresponding to the measurement light output from the photoelectric conversion means. a calculation means that calculates the ratio of the electric signal corresponding to the reference light and the electric signal corresponding to the measurement light by inputting the above, and calculates the gas pressure at the gas pressure measurement point based on the calculated ratio; An optical gas pressure sensor comprising: display means for displaying calculated gas pressure.