JPS6197540A - Temperature measuring apparatus - Google Patents

Abstract

PURPOSE:To enable a stable measurement of temperature regardless of changes in the light source power and changes in the loss of an optical fiber, by receiving light with two photoelectric converters different in the wavelength sensitivity to determine the output ratio thereof. CONSTITUTION:Light from a light emitting diode 1 is introduced to a tempera ture sensor 2 with a first optical fiber 3a and the transmission light power 10 varies with the temperature sensor adapted to very in the degree of the wavelength absorption depending on the temperature. Then, the transmission light is introduced to a photo distributor 4 through a second optical fiber 3b. The light is divided in two directions and converted into light from electricity with a silicon based photodiode 5 and a germanium based photodiode 6 separate ly. In this case, outputs thereof vary with the measured temperature but the damping characteristics 11 and 12 are difference between the photodiode 5 having a characteristic 5a of lowering the output biased to the long wavelength and the photodiode 6 having a characteristic 6a of lowering it biased to the short wavelength. Thus the radio 13 of the outputs is determined with an arith metic circuit 9 to obtain the function of the temperature thereby enabling accu rate measurement of the temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a temperature measuring device that makes use of the fact that the wavelength absorption increase changes depending on the temperature.

[Conventional technology]

This type of conventional temperature measuring device uses the temperature dependence of the absorption wavelength of a semiconductor, in which the light wavelength absorption #M changes depending on the light from the light source and the temperature. The measurement temperature was determined based on the results.

Problem 3 to be Solved by the Invention C However, there is a drawback that changes in the optical backlash of the light source and the optical fiber loss serving as the optical path directly affect the measured temperature, making accurate temperature measurement difficult.

This invention has been made to overcome the drawbacks of the conventional devices, and its purpose is to provide a temperature measuring device that can perform stable temperature measurements despite changes in the power of the light source and changes in the loss of the optical fiber. .

[Means for solving problems]

The temperature measuring device according to the present invention is equipped with an arithmetic circuit that receives light with two optical/electrical converters having different wavelength sensitivities and calculates the output ratio thereof.

[Effect]

In this invention, the light transmitted through the temperature sensor is received by two optical/electrical converters with different wavelength sensitivities and the output ratio is calculated, so that changes in the power of the light source and changes in the loss of the optical fiber are canceled out.

〔Example〕

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

FIG. 1 is a block diagram showing the configuration of a temperature measuring device in an embodiment of the present invention. In the figure, (1) is a light emitting diode as a light source, and its emission wavelength intensity distribution is
This is shown in characteristic (1a) in the figure. (2) is GaAa, CdTe
, is a temperature sensor made of a semiconductor such as GaP whose optical wavelength absorption edge changes, and its absorption #: length changes from low temperature (2a) to high temperature (2b) as shown in FIG. (3a
) is the temperature sensor (2) that uses the light emitted from the light emitting diode (1).
(3b) is the temperature sensor (2).
A second optical fiber (5) is an optical/electrical converter that converts one of the lights distributed by the optical splitter (4) into an electrical signal. , as shown in characteristic (5a) in Figure 3, the wavelength is 800 to 1000 m.
It is composed of a silicon-based photodiode, which has poor sensitivity on the long wavelength side. (6) is also an optical splitter (4).
It is an optical/electrical converter that converts the other light distributed by
It is composed of a germanium-based photodiode that has poor sensitivity on the short wavelength side for wavelengths from 00 to 1000 m. (7)
(8) are the respective photodiodes (5) and (6).
), (9) is an amplifier circuit that amplifies the output of (7)
(8) This is an arithmetic circuit that calculates the ratio of outputs.

Next, the operation will be explained. The light emitted by the light emitting diode (1) is guided to the temperature sensor (2) by a first optical fiber (3a). Here, the fourth transmitted light is guided to a light splitter (4) that separates the light into two directions via a second optical fiber (3b). Here the light is in two directions VC9
Light/
As shown in Figure 5, the respective outputs vary depending on the measurement temperature, but there is a silicon-based photodiode (5) that has a characteristic (5a) that decreases in the long wavelength band, and a silicon photodiode (5) that decreases in the short wavelength band. The germanium-based 7-otodiode (6), which has the characteristic (6a), has the respective attenuation characteristic (
11) and (12) are different, and the humidity function can be obtained by attacking the ratio (13) of these using the arithmetic circuit (9). Changes in the power of the light source (1) and changes in loss in the optical path such as the optical fibers (3a) (3b) are canceled out during the calculation process of the ratio and do not affect the final output.

Above is light! Although a light emitting diode is used as (1), a light source with a wavelength distribution such as an incandescent bulb may also be used.

Furthermore, although silicon-based photodiodes and germanium-based photodiodes were used as the optical/electrical converters (5) and (6), similar effects can be achieved if optical/electrical converters with different wavelength characteristics are used. Furthermore, although the function of the arithmetic circuit output and temperature has been described, the relationship between temperature and output can be made proportional and linear by analog/digital conversion, ROM (read only memory), and digital/analog conversion.

〔Effect of the invention〕

As explained above, this invention converts the transmitted light of a temperature sensor into electricity using an optical/electrical converter with different wavelength characteristics, and calculates the ratio. This has the effect that temperature can be measured accurately without being influenced by

[Brief explanation of drawings]

Fig. 1 is a Glock diagram showing the configuration of a temperature measuring instrument according to an embodiment of the present invention, Fig. 2 is a diagram of the optical power of the light source and the wavelength characteristics of the optical wavelength absorption edge of the temperature sensor, and Fig. 3 is a photodetection diagram of the photodiode. FIG. 4 is a sensitivity-wavelength characteristic diagram, FIG. 4 is a temperature characteristic diagram of transmitted light power, and FIG. 5 is a temperature characteristic diagram of each light reception and calculation output. In the figure, (1) is a light emitting diode as a light source, (
2) is the temperature sensor, (3a) and (3b) are the first
and second light 7I/I, (4) is a light distributor, (5) (
6 is a silicon thread and a germanium-based photodiode as a light/electrical converter, respectively, and (9) is an arithmetic circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa Figure 1 Ja, Jh Ya 11 off 0 lights off hi. 4, nine distribution five j, lr:'/licon f-4L)-ke) Remanicum series,
Photo 2゛Sai-do 9゛ Desert 1st Port Figure 2 Figure 4 Figure 3 Figure 5

Claims (3)

[Claims] (1) A single light source, a temperature sensor made of a semiconductor whose optical wavelength absorption edge changes depending on temperature, a first optical fiber that guides the light from the light source to the temperature sensor, and a first optical fiber that guides the light transmitted from the temperature sensor to the temperature sensor. an optical splitter that receives light through two optical fibers and divides it into two lights; an optical/electrical converter with mutually different wavelength sensitivities that converts the two lights into electrical signals; and a ratio of the converted electrical signals. What is claimed is: 1. A temperature measuring device comprising an arithmetic circuit for calculating the temperature from the ratio. (2) The temperature measuring device according to claim 1, wherein the light source is a light emitting diode or an incandescent light bulb with stable wavelength intensity. (3) Wavelength 800-1000mm as a light/electrical converter
In contrast, a silicon-based photodiode whose sensitivity deteriorates on the long wavelength side and a germanium-based photodiode whose sensitivity deteriorates on the short wavelength side are used in pairs. Temperature measuring device according to item 2.