JPH0262936A - Hygrometer - Google Patents

Abstract

PURPOSE:To improve follow-up performed and responsiveness to temperature variation and humidity variation by using an optical fiber for signal transmission from a sensor and then providing the hygrometer which is a sensor part and a part of the optical fiber although it is installed in humid environment. CONSTITUTION:Sensors 8 are formed of porous glass as water adsorbing carriers atop of optical fibers 7, 10, and 70, and specular surface parts 9 are formed on their end surfaces by metal coating. Light emitted by a light emission part 6 passes through an optical system and the optical fibers 7 and 70 and is project ed in the sensors 8 and reflected by the specular surfaces 9 to return a hygrome ter main body 5 through the optical fiber 10; and the quantities of attenuation of the reflected light beams are measured to measure humidity by a part 14. Then two wavelengths in the infrared-ray range are selected for light for measur ing the amount of adsorbed water and the absorption zone and nonabsorption zone of water are set to increase detection sensitivity, thereby removing the influence of a disturbing element. Further, the optical fibers are coated with 'Teflon(R)' which adsorbs no water to remove an error due to the adsorption and desorption of water.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hygrometer using optical fibers used for environmental measurement and control.

[Prior art 1] Conventional hygrometers that have a one-word electrical output that can be used to measure and control humidity include hygrometers that utilize the moisture absorption phenomenon of objects, and hygrometers that do not utilize the moisture absorption phenomenon of objects. 2
? It is broadly classified into type l.

Hygrometers that utilize the moisture absorption phenomenon of objects include those that utilize the resistance change due to swelling of polymer resins mixed with conductive powders such as carbon powder and gold i powder, and moisture meters that utilize moisture absorption of polymer resins. There are some that utilize static electricity and capacitance changes, and others that utilize resistance changes due to moisture adsorption in ceramics.

These hygrometers use materials with high moisture adsorption capacity as sensor materials, which allows them to capture a large amount of moisture through the phenomenon of moisture adsorption in a small volume. It is characterized by the ability to easily convert changes into electrical signals.

For this reason, the humidity detection mechanism and circuit configuration are pure,
As a result, the entire device is small, lightweight, and highly portable. Furthermore, these hygrometers have a separate humidity detection section, so they are easy to install, relatively inexpensive, and are used in large numbers.

However, despite the fact that the sensor itself is made smaller by utilizing the moisture adsorption phenomenon of objects, these humidity h1s require a circuit inside the humidity detection unit to convert resistance changes or capacitance changes into electrical signals. As a result,
The humidity detection part becomes larger than the sensor itself, and the ability to follow temperature and humidity changes deteriorates, making measurement i, P
This results in a difference of 1. Further, since the electric circuit is installed inside the humidity detecting section, leakage occurs over time under high temperature and high humidity measurement environments, leading to failure and damage.

On the other hand, hygrometers that do not utilize the moisture adsorption phenomenon of objects include optical dew point meters that detect dew condensation on a cooled mirror surface by changes in light reflectance, and alpha-ray absorption meters that detect dew condensation in a cooled ionization chamber. A dew point meter that captures water molecules in gases, a microwave individual meter that captures water molecules in gas using microwave absorption, and an infrared i! that measures wood molecules in gases by absorbing infrared rays. There are ii1 degree meters, etc.

Although these hygrometers are generally highly accurate, they do not utilize the moisture adsorption phenomenon of objects, so they do not require cooling the mirror surface or electric box, enlarging the microwave resonance system, or increasing the infrared optical path length. The ability to detect humidity is obtained by increasing the length of the sensor. Therefore, the humidity detection section cannot be separated, the circuit becomes complicated, and the entire device becomes large and expensive.

[Problems to be Solved by the Invention] Conventionally, for example, in the hygrometer shown in FIG.
It is supposed to be fucked. Here, 3 is a four-dust filter, 4 is a signal transmission cord, and 5 is a hygrometer body.

Moisture adsorption carrier sensor 1 that utilizes the moisture adsorption phenomenon of objects
is designed to be small, have a small heat capacity, and have a fast response due to adsorption and desorption of moisture, whereas the first stage converter 2 has a circuit for converting the resistance change or capacitance change of the sensor 1 into an electrical signal. is quite large, so as a result,
The entire humidity detection section is larger than the sensor itself,
The ability to follow changes in humidity and humidity changes is poor, and the advantage of making the sensor smaller by utilizing the attraction phenomenon of objects cannot be fully utilized, resulting in measurement errors.

In addition, in a high temperature and high humidity environment, the sensor 1 and the first stage converter 2
There were problems with reliability, such as leaks occurring over time in the seals of the first stage converter 2 and the cord 4, leading to breakdowns and failures.

By using light to transmit signals from the sensor, this Komei eliminates the first-stage conversion, takes full advantage of the miniaturization of the sensor, and improves the ability to follow temperature and humidity changes. Furthermore, by fundamentally eliminating electrical leakage, the aim is to provide a hygrometer that is small, light, responsive, highly heat resistant, and highly reliable. .

[Means for Solving the Problem 1] The present invention forms a porous glass portion as a moisture adsorption carrier at the tip of an optical fiber, and forms a mirror surface portion such as a metal coating on the surface of this porous glass portion to create a sensor. By measuring the amount of moisture adsorbed in the porous glass according to the humidity in the measurement condition, the attenuation of the light that is projected through the optical fiber, passes through the porous glass, and is reflected by the mirror surface. , which attempts to measure the humidity in the measurement environment.

Here, by using infrared light having an absorption band of water as the light for measuring the amount of adsorbed water, detection sensitivity can be further increased.

Furthermore, by selecting two wavelengths in the infrared region of light, setting one wavelength in the absorption band of water and the other wavelength in the non-absorption band of water, it is possible to eliminate the influence of disturbance elements. I can do it.

[Function] In the hygrometer configured as described above, the porous glass portion serving as the sensor and a portion of the optical fiber serving as the signal transmission portion are installed in a humid environment. As a result, the heat capacity of the humidity detection section becomes extremely small, and the ability to follow temperature is improved, and the ability to follow humidity, which is a function of temperature, is also improved.

Furthermore, by coating the optical fiber with Teflon, which does not absorb moisture, it is possible to eliminate errors caused by adsorption and desorption of moisture on the surface of the optical fiber placed in a humidity measurement environment.

Furthermore, by using optical fiber for reliable transmission, we do not bring electrical circuits into the humidity measurement environment, fundamentally solving failures and damage caused by electrical leaks over time, and improving heat resistance. It also satisfies explosion-proof safety.

[Example] To clarify the example with reference to the drawings, in Fig. 1, an optical fiber 7.10.70 which is a signal transmission line is
A porous glass sensor 8 as a moisture adsorption carrier shown in FIG. 2 is formed at the tip of the sensor 8, and a mirror surface portion 9 made of metal coating or the like is formed on the end surface.

Light emitted from a light emitting part 6 such as a light bulb in the hygrometer body 5 passes through a lens 61, a mirror 62, etc., passes through a light-emitting optical fiber 7, and is projected into a porous glass sensor 8 at the tip of an optical fiber 70. The light is reflected by the mirror surface of the end surface of the porous glass and returns to the hygrometer main body 5 through the light-receiving optical fiber 10.

At this time, the wavelength of the water absorption band of the projected light is absorbed by the water adsorbed in the porous glass sensor 1, and is significantly attenuated compared to the wavelength of water's non-absorption band.

The light that returns to the hygrometer main body 5 through the light-receiving side/optical fiber 10 passes through the optical fiber 11a provided on the sector 11 rotated by the motor 13, and then passes through the optical fiber 11a provided on the sector 11 rotated by the motor 13, and then passes through the optical fiber 11a provided on the sector 11, which is rotated by the motor 13. The light is divided into light and light having a wavelength in the non-absorption band of water, for example 1.6 μm, and is alternately irradiated onto a light receiving unit 12 such as a photodiode, and converted into an electrical signal.
The output signal for these two wavelengths is subjected to calculation processing such as ratio calculation in the calculation means 14, and then displayed on the display means 15 as a humidity value, and is also transmitted to other equipment as a signal output. Note that the sector 11 may be provided on the light projection side to project light of two wavelengths.

[Effect of the invention 1] The hygrometer configured as described above has a
What will be removed are the porous glass part, which is the senna, and a part of the optical fiber, which is the signal transmission part. As a result, the heat capacity of the humidity detection section becomes extremely small, and the ability to follow temperature is improved, and the ability to follow humidity, which is a function of temperature, is also improved.

In addition, optical fibers are coated with Teflon, which does not absorb moisture.
By overturning, it is possible to eliminate errors caused by moisture absorption on the surface of the optical fiber placed in a humidity measurement environment.

Furthermore, by using optical fiber to transmit No. 1, no electrical circuits are brought into the humidity measurement environment, which fundamentally solves the problem of failures and deterioration over time due to electrical leaks.
It improves heat resistance and satisfies intrinsically safe explosion protection.

[Brief explanation of the drawing]

1 and 2 are configuration explanatory diagrams showing one embodiment of the present invention,
FIG. 3 is a diagram showing the absorption characteristics of water in the infrared wavelength region, and FIG. 4 is an explanatory diagram of a conventional example.

Claims (1)

[Claims] 1. Porous glass as a moisture adsorption carrier formed at the tip of an optical fiber, a mirror surface portion formed on the end surface of this porous glass, a light emitting portion that projects light through the optical fiber, and a porous glass A hygrometer comprising: a light-receiving section that receives light reflected by a mirror surface of a glass end surface; and a calculation means that calculates humidity from the output of the light-receiving section. 2. The hygrometer according to claim 1, wherein the light projected through the optical fiber is infrared rays having an absorption band of water. 3. The hygrometer according to claim 2, wherein the infrared rays projected through the optical fiber have two wavelengths: one in the absorption band of water and one in the non-absorption band of water.