JPS6196427A - Temperature measuring instrument - Google Patents

Abstract

PURPOSE:To ensure accuracy by observing the light transmitting a temp. sensor with a spectrograph, by detecting the photoelectrically converted electrical signal on plural varying levels and by processing with an operation the rising point of the absorption end from respective position of the lowest wavelength side. CONSTITUTION:The temp. sensor 9 consisting of the semiconductor crystal of a gallium, arsenide, etc. is fitted to optical fibers 2, 4, the light transmitted from a light emitting element 6 is led to the sensor 9, the transmitted light is made spectra by a diffraction grid 15 and after its photoelectric conversion in time series by a CCD19 it is compared on two levels by two pieces of comparators 17-1, 17-2. The respective position of the lowest wavelength side is detected by the processing circuit to find the point where the transmitted light regarding the absorption terminal as a straight line is made in zero. A correct temp. measurement is thus enabled without causing the temp. errors even in case of the change of either the light intensity of light emitting element or the center wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a Fim degree measuring device, and more particularly to a temperature measuring device using a material whose absorption edge of the wavelength of light changes depending on the temperature.

"Prior Art" Figure 3 is a block diagram of a conventional temperature measuring device, in which (1) is a light emitting element drive circuit, (6) a light emitting element as a Vi light source, (
2) and (4) are optical fibers, and (9) is a temperature sensor that uses a material whose light transmittance changes depending on the absorption edge of the wavelength of light, such as a semiconductor crystal such as GaAs or an amorphous material. The optical fibers (2) and (4) are sandwiched between tubes and fixed with adhesive. (15) is a diffraction grating as a spectrometer, (16) is a photodiode array, (1
7) is a comparator connected to each element of the 7-otodiode array (16), and (is) is a processing circuit. FIG. 4 is a characteristic diagram showing an example of the relationship between the wavelength dependence of the temperature sensor (9) and the temperature. As the temperature increases, the light absorption edge moves to the longer wavelength side. FIG. 5 is a diagram showing the spectrum of the light emitting element (6) and the spectrum of transmitted light from the temperature sensor (9).

Next, the operation will be explained. In FIG. 3, a light emitting element (6) is driven by a light emitting element driving circuit (1).

When the spectrum fiLEDt- of this light emitting element (6) is used, a normal distribution as shown in FIG. 5 is obtained. If the light absorption edge of the temperature sensor (9) is selected to be within this spectrum, the absorption edge will shift as shown in Figure 4 depending on the temperature at which the temperature sensor (9) is placed. The transmitted light has a spectrum shown by diagonal lines in FIG. Therefore, the light emitted from the optical fiber (4) is separated by a diffraction grating (15), each of the separated lights is photoelectrically converted by a photodiode array (16), and each comparator outputs at a certain level or higher in each array element. (17) is provided, and a processing circuit (18) calculates the position of the lowest wavelength of the transmitted light of the temperature sensor (9) among the outputs of the comparator (17).

[Problem to be Solved by the Invention 3] Since the conventional temperature measuring device is configured as described above, there is no possibility that the light intensity or center wavelength will change significantly due to temperature changes or changes over time of the light emitting element (6). If there is a temperature sensor (
Since the absorption edge characteristic of 9) does not have a perfect linear rise, there is a problem in that an error occurs.

This invention was made to solve the problems of the conventional ones as described above, and it is possible to accurately measure temperature even if there is a large change in the light intensity or center wavelength due to temperature changes or changes over time of the light source. The purpose is to obtain a temperature measuring device.

[Number of steps taken to resolve the problem]

The humidity measuring device according to the present invention detects the level of Ml power using a plurality of repeaters, and calculates the rising point of the absorption edge of the temperature sensor from the position on the lowest wavelength side of each. .

[Operation] In this invention, since the temperature is measured by calculating the rising point of the absorption edge of the temperature sensor from the position on the lowest wavelength side at multiple levels, there is no temperature error even if the light intensity or center wavelength of the light source changes. does not occur.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, and the same numbers as in FIG. 3 indicate the same components. In Figure 1, (
19) is a CCD (Charged Coupled
Device), (17-1), and (17-2) are comparators that operate at mutually different levels, and (2
0) is a processing circuit.

Figure 2 shows the spectrum of transmitted light from the temperature sensor (9). The relationship between the rise of the absorption edge when there is a change in the light intensity of the light emitting element (6) is shown in the figures (a) and (b).

Next, the operation will be explained. The light transmitted through the temperature sensor (9) passes through an optical fiber (4), is separated by a diffraction grating (15), is photoelectrically converted in time series by a COD (19), and is simultaneously connected to two comparators (17-1), (17-2)
are compared on two levels. By the way, if we consider the case where the light intensity of the light emitting element (6) changes, as shown in FIG. 2 (a) and (b), the temperature sensor (9)
In the shaded area showing the transmission spectrum of , the rise of the absorption edge (marked with an X in the figure) point Iri does not change. Therefore, if we detect the positions λ11λ2 on the lowest wavelength side at the two levels Ll and L2, and from these values, consider the absorption edge as a straight line and find the point where the transmitted light becomes zero, λ0
is determined, and this value does not change even if the light intensity of the light emitting element (6) changes. The above also applies when the center wavelength of the light emitting element (6) changes. Therefore, these calculations are performed by the processing circuit (20). This calculation can be easily performed by digital processing using, for example, a microprocessor.

In the above embodiment, the absorption edge is regarded as the ml line and the wavelength λ0 of the rising point is calculated from the wavelength λlλ2 at two levels, but it is detected at more levels and from those values λn'c@ Calculation processing allows for even more accurate measurements.

〔Effect of the invention〕

As explained above, this invention calculates the temperature by calculating the rising point of the absorption edge of the temperature sensor from the position on the lowest wavelength side at multiple levels, so even if the light intensity or center wavelength of the light source changes, it will not be accurate. It has the effect of being able to measure temperature.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the transmitted light spectrum and operation level of the temperature sensor when the light intensity of the light emitting element changes, and FIG. 3 is a diagram showing the conventional A configuration diagram showing the temperature measuring device, Figure 4 is a diagram of the relationship between the wavelength dependence of the temperature sensor in Figure 3 and temperature, and Figure 5 is a diagram of the relationship between the spectrum of the light emitting element in Figure 3 and the transmitted light of the temperature sensor. FIG. In the figure, (2) and (4) are optical fibers, (6) is a light emitting element as a light source, (9) is a temperature sensor, (15) is a diffraction grating as a spectrometer, (19) is a COD, and (20) is a processing circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A temperature sensor made of a material whose absorption edge of the wavelength of light changes as a function of temperature is provided in the path of the optical fiber, the light from the light source is guided to the temperature sensor, and the light transmitted through the temperature sensor is collected using a spectrometer. In devices that measure the temperature from the lowest wavelength of the wavelength component of the optical output by spectroscopy and converting it into an electrical signal, the electrical signal is detected at multiple mutually different levels, and the lowest wavelength side position operated at each of the above levels is detected. A temperature measuring device characterized in that the rising point of the absorption edge is calculated from . (2) Detecting electrical signals at two mutually different levels,
The temperature measuring device according to claim 1, wherein the absorption edge characteristic is regarded as a straight line, and the rising point of the absorption edge is calculated by linear approximation from the lowest wavelength side position operated at each of the above levels. .