JPS6017327A - Measuring device of temperature - Google Patents

Abstract

PURPOSE:To attain highly accurate measurement by constituting an integrating means with a VF converting circuit and a counting means in a temperature measuring device using an integrating value at a prescribed time band of an afterglow signal of a phosphor of which phosphor decay characteristics have temperature dependence. CONSTITUTION:The phosphor 2 is fitted to the leading end of an optical fiber 1 to constitute a temperature probe. When a pulse P1 is inputted from a CPU10, excited light is outputted from a light emitter 3 to irradiate the phosphor 2. The fluorescence and afterglow from the phosphor 2 are converted into electric signals by a photodetector 5 through a beam splitter 9. A timing pulse P2 is outputted during a period from time ta after falling, of the pulse P1 to time tb and the VF converting circuit 7 converts an afterglow voltage signal into frequency during a period from the time ta to the time tb and outputs a pulse signal S. The signal S is counted up by a counter in the CPU10 and the afterglow integrating value of the phosphor 2 is found out as a counted value and compared with the temperature characteristics to find out the temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION Background of the Invention The present invention relates to a light temperature determining device using a phosphor.

Optical temperature measurement uses electrical signals (1, so it is completely unaffected by noise caused by electromagnetic fields), and various devices using optical fiber technology have been developed. has been done. In particular, phototemperature measurement using the light emitted from the fluorophores is difficult because the wavelength of the light is converted during the excitation-emission process of the fluorophores. It has the advantage of being able to separate light from the fluorescence and afterglow from the phosphor. Therefore, input and output light can be transmitted using (using) the single optical fiber 2, making the optical transmission system compact.

Fluorescent-applied temperature measurement technology can be roughly divided into two types: those that utilize temperature changes in the W intensity of fluorescent light, and those that utilize temperature changes in the afterglow time after excitation stops, which simultaneously detect small fluorescent lights. In order for these to exist, they must be heated by wavelength using spectroscopy or other methods, which requires an optical system and also has the disadvantage that measurement with a high S/N ratio is difficult. On the other hand, in temperature measurement that uses temperature changes in afterglow, the afterglow, which is the light after the excitation stops, is detected, so in principle, it is possible to measure the temperature without affecting the excitation light or afterglow measurement. It has the advantage of being easy to measure. However, a typical afterglow time measurement is when the excitation stops or the brightness is 90% of the peak brightness at the excitation stop.
It measures the time from when the brightness reaches 10% of the peak brightness to when the brightness reaches 10% of the peak brightness, and the point on the afterglow curve at which these measurement points fall will be determined when the measurement is completed. Since all the signal components forming the afterglow curve are to be measured, there is a drawback that the measurement accuracy is easily affected by sudden or partial signal changes during the measurement process due to noise or the like. In addition, since afterglow time measurement is a measurement of afterglow intensity during the decay process of afterglow, it is difficult to measure low afterglow intensity, and errors tend to occur in determining when afterglow intensity reaches zero. There is a problem in that the photoperiod cannot be measured accurately. That is, the afterglow curve decreases exponentially or hyperbolically, and the curve changes very gradually in areas where the afterglow brightness is extremely small. However, in determining the point in time when the afterglow brightness reaches 10% of its peak, it is inevitable that the error will become large.

Summary of the Invention This invention makes it possible to eliminate the harmful effects of excitation light by measuring afterglow temperature changes, and also uses a new measurement quantity instead of the conventional afterglow time measurement. An object of the present invention is to provide a fluorescent-applied optical temperature measuring device that can accurately measure humidity.

The humidity measuring device according to the present invention is arranged in an atmosphere or an object whose humidity is to be measured, and includes a phosphor having an afterglow property or temperature dependence, an excitation means for exciting the phosphor, and a device that emits light from the excited phosphor. a light receiving means for detecting the afterglow of the received light and converting it into an electrical signal; an integrating means for integrating the received afterglow signal over a predetermined time period to obtain an afterglow integral light amount; and an afterglow integral. It consists of a calculating means that calculates the temperature by comparing the scene with the temperature characteristic of the integral value of the afterglow scene set in advance according to the phosphor, and the integrating means or the received afterglow electric signal is It is characterized in that it is comprised of a V7F conversion circuit that converts into a pulse signal of a frequency corresponding to the magnitude, and a counting means that counts the output pulses of the V7F conversion circuit over the predetermined time period. A counter or a microprocessor can be used as counting means.

The integration time period may be fixedly determined in advance depending on how the afterglow is generated, or may be determined based on the value of the afterglow signal.

In the humidity measuring device of the present invention, temperature is measured using the integral value of the afterglow signal in a predetermined time period. Therefore, unlike conventional devices that measure afterglow time, it is less affected by sudden or partial signal changes due to noise, etc., and does not perform level discrimination at low brightness signal levels. It is possible to increase the viscosity of the measurement. Furthermore, since the afterglow is measured, there is no need to separate it from the excitation light, making it possible to measure a high SlN ratio without being adversely affected by the excitation light, and also eliminating the need for a spectroscopic device.

In general, the rate of change in brightness at a specific point in the afterglow process is greater than the temperature change in afterglow time, and it changes monotonically with temperature, so fluorescent light can be used as a sensor for temperature measurement. The selection range of the body is wide, and in this respect, the device according to the present invention has superior effects compared to conventional devices that measure afterglow time. This can be explained logically as follows.

Assuming that the afterglow signal decreases exponentially, the afterglow characteristic is expressed by the following general formula.

Yaw I (L)ゞAeIO's・C−τ(sword・war), (1) Here, T is the temperature, or the time measured from the point of stopping the excitation,
I(v) is the afterglow brightness at time (1), IO (sword is the afterglow brightness at the excitation stop point (L-0), τ(T)
is the average lifetime of the excited state in the phosphor, and A is the proportionality constant. Among these parameters, those that change with temperature T are lo(1) and τ, and the change in τ■ with temperature appears as a change in afterglow time with temperature.

If the afterglow time td is the time required for the afterglow brightness to decay to 10% from the point of excitation stop, then this time t
d is given by the following equation.

From equation (2), it can be seen that even if the temperature change (■0σ) shows a large value, if the temperature change τ■ is small, the temperature change in the afterglow time Ld is also small.

On the other hand, the integral value l1nt(T) of afterglow brightness used in the present invention is given by the following equation.

Here, ta and tb are the start and end times of the integration time period, respectively. From equation (3), it will be understood that even if the temperature change in τ■ is small, the integral value l1nt(17) changes greatly in accordance with the temperature change in lo(T). For this reason, the present invention allows extremely accurate temperature measurements. Furthermore, since temperature change in peak brightness l0 (I'), that is, temperature quenching property, is the most common property of phosphors, the range of selection of phosphor materials applicable to this invention is expanded, and the desired temperature change can be achieved. This makes it easier to adjust the phosphor shown.

In Japanese Patent Application No. 57-64177, the inventors have already proposed a temperature measuring device that calculates the integrated amount of afterglow light by integrating the received afterglow signal over a predetermined time period. As an example of an integrating means in this temperature measuring device, an afterglow signal is sampled at predetermined time intervals, A/D converted, this afterglow sampling data is stored in a memory, and the stored sampling data is added. A system that utilizes a microprocessor has been disclosed. In measurement by this integrating means, since the afterglow signal is sampled at predetermined time intervals, there is a problem in that the final added value does not necessarily represent an accurate integrated value.

This drawback is particularly noticeable when the afterglow waveform changes sharply. It is possible to solve this alignment by shortening the ic At, s7 fling Rrrs"r and increasing the number of sampling points, but if this is done, the high speed A/
A new problem arises in that a D conversion device is required and the amount of data is enormous, requiring a high-grade processing device. Also, in the above integration means, A/
Dispersing errors in D conversion also greatly affect waveform measurement accuracy.

In this invention, the integrating means is constituted by a combination of a V/F conversion circuit and a counting means. (2) The magnitude and voltage of the afterglow electrical signal are continuously converted into the frequency of a pulse signal by the /F conversion circuit, and by counting these pulse signals, the above-mentioned integrated value of the amount of afterglow light is determined. The afterglow brightness is continuously and accurately reflected by the frequency of the pulse signal, and since there is a large amount of data, and it is possible to respond to sudden changes in the afterglow brightness, highly accurate measurement is possible.

In the present invention, various types of phosphors can be used without being limited as long as they have temperature-dependent afterglow characteristics and a measurable afterglow time. Preferably, the afterglow time is 1. ．． A phosphor of about 0-6sec to 31Qsec is preferable. For example, in ultraviolet light excitation, rare earth metal oxysulfides such as Y2O25i:Eu, sulfide phosphors such as ZnS:Ln (T and n are generic terms for rare earth elements), SrS:Ln, and C
Many types of RT phosphors can be used. In addition, in infrared light excitation, L nFa: (Yb, Er), La OF:
(Y b, Er), L i N d P 4012
:Yb etc. are used.

DESCRIPTION OF EMBODIMENTS The present invention will now be described in more detail with reference to the drawings.

FIG. 1 shows pulsed or square-wave excitation light and the waveform of light emitted from a phosphor excited by the excitation light, and shows that the light emitted from the phosphor varies depending on temperature.

The light emitted during excitation is fluorescent light, and the light emitted after the excitation stops (indicated by tX) and attenuates over time is afterglow. Among the waveforms of fluorescence and afterglow, those shown by broken lines are the waveforms at temperature T1, and those shown by solid lines are the waveforms at temperature T2. Here T.I.
The relationship is <T2. Generally, afterglow brightness tends to increase as the temperature decreases.

FIG. 2 shows the temperature characteristics of the integral value of the amount of afterglow light.

The integral value (pulse count value) of the phosphor used is measured in advance at various temperatures T, and the integration time period when creating the characteristics shown in Figure 2 as a known relationship in advance is determined by this characteristic. coincides with the integration time period of the temperature measuring device used.

FIG. 3 shows the configuration of the temperature measuring device, and FIG. 5 shows its operation. A predetermined fluorescent material (2) is attached to the tip of the optical fiber (1), forming a temperature probe. The temperature probe is placed with its tip in contact with the atmosphere or object whose temperature is to be measured. C.P.
Two types of timing pulse signals PL and P2 are output directly from the timing generation circuit or CPU (101) controlled by U (101. Pulse P1 is
It is for driving the light emitter (3) and is output at a constant period T'a. This period Ta is set to a time sufficient for the afterglow emitted from the phosphor (2) to completely disappear at all temperatures within the measurement range. When the pulse Pi is input, excitation light is output from the light emitter (3) and is irradiated onto the phosphor (2) through the optical fiber (1). The fluorescence and afterglow emitted from the phosphor (2) by this excitation propagate through the optical fiber (1), and the beam
It is taken out via a splitter (9) and converted into an electrical signal by a photoreceiver (5). The detection signal of the photoreceiver (5) is amplified by the preamplifier (6) and then converted to voltage/frequency (V
/F) Input to conversion circuit (7).

The timing pulse P2 determines the integration time period, and is output from a time La after the falling edge of the pulse P1 to a time L1+ after an appropriate period of time has elapsed. The time periods ta to tb are appropriately determined in consideration of the reproducibility of the data to be captured. In other words, the V/F conversion circuit (7)
The time should be such that the count value of the output can be made sufficiently large. In this embodiment, the starting point ta of the integration time period is set at the time t1 when excitation is stopped. The end point Mo1) of the integration time period is constrained by the afterglow level at the second limit temperature of the constant temperature range in which the afterglow is the lowest *+ degrees. For example, the end point th may be defined as the point in time when the afterglow level at this upper limit temperature becomes about 30% of the peak brightness (1517 degrees at the time of stopping the excitation). If a sufficient number of pulses can be obtained from the v/F conversion circuit (7), set the integration time period to a relatively short time, for example, set the starting point La to 1 when the excitation is stopped;
The end point 1]) can be set at the time when the afterglow level reaches 90% of the peak brightness, and sufficient measurement accuracy can be obtained even in such a case.

By shortening the integration time period, temperature measurement can be made faster. Even when a phosphor with a relatively long afterglow time is used, the proportion of the integration time period in the afterglow time can be made small.

However, since this invention does not measure the afterglow time but measures the afterglow integrated light amount, it has the feature that accurate measurement is possible even if the integration time period is relatively short.

The V/F conversion circuit (7) continuously converts the input afterglow voltage signal into a frequency corresponding to the voltage value during the integration time period a to tb, and outputs a pulse signal S of that frequency. The pulse signal S continuously changes from dense to sparse as shown in FIG.

This signal S is counted by a counter. Even if you use a counter installed outside the CPU f101,
It may be implemented using memory or registers within the CPUflO1.

RAM (12+, as shown in FIG. 4, has an area for storing the integrated light amount (counter count value) for each measurement, an area for storing the number of repetitions m of the noggles P1, and a second An area is provided for storing the temperature characteristics of the integrated value of the amount of afterglow light shown in the figure.In this embodiment, the excitation of the phosphor (2) is repeated m times, and the integrated value of the amount of afterglow light is The temperature is determined based on the added value (or average value).

Timing number pulse P1. Every time P2 is output, the integrated value of the amount of afterglow light of the phosphor (2) is obtained as the count value of the counter, and this is stored in RAM (12+). Then, when m measurements are completed, each count is The numerical values are added and this added value is compared with the temperature characteristic to calculate the temperature T. It goes without saying that the integral value (counted value) in the temperature characteristic is also stored in advance as the m-times added value. This temperature characteristic (function) is expressed graphically in Figure 4, but of course it is also expressed in the form of a table RAM (12
It is stored in +.

An example of a measurement result is the afterglow time at a certain temperature.
Using 5 mS phosphors YFa:Yb, , Er, the integration time L aNL b was 5: m'S, and the timing.
The number of repetitions of pulse Pi is 100/sea.

When using a v/F conversion circuit of ft1t large IM pulse/sec, the addition count value of 1.5X10 (10
0 doses) were obtained. The temperature change of this count value is 7/1 (
0'C/#'C), and a practically sufficient resolution was obtained.

In the above example, the end point vb of the integration time is fixedly determined in advance, but it may be determined depending on the level of the afterglow signal. That is, the brightness level IS for determining the end point tb
Determine in advance. Then, the point in time when the afterglow signal reaches this level IS is defined as the end point L1).

In the above embodiment, the period Ta of excitation of the convoluted light body is
The time period is set to be long enough for the afterglow to completely disappear, but by shortening this period Ta, the next pulse P1 is output during the afterglow process to excite the phosphor and create a dynamic It takes advantage of the afterglow response and is not used for temperature measurements. According to this method, temperature measurement can be made faster.

[Brief explanation of the drawing]

Fig. 1 is a waveform diagram showing excitation light, fluorescence emitted from a phosphor, and afterglow, Fig. 2 is a graph showing temperature characteristics of integrated amount of afterglow, and Fig. 3 shows an example of the present invention. 4 is a diagram showing the contents of the RAM, and FIG. 5 is a time chart showing the operation of the circuit shown in FIG. 3. (1)...Optical fiber, (2+---fluorescent material, (3
)...Emitter, (5)...Receiver, (7)・No.・V
/F conversion circuit, (10)・-CPU (12+...
RAM 0 or more 4 other persons procedural amendment August 1981 lθ day 1, case indication 1982 Patent Application No. 125178 2
, Title of the invention Temperature measuring device 3, Relationship to the case of the person making the amendment Patent applicant - Address 8.2, 10 Hanazono Tsuchido-cho, Ukyo-ku, Kyoto City
Yu (29 Yutateishi Electric Co., Ltd. 4, agent Tae;
! Kakusho Shigeko Tokyo (I3+';) 7184 Tachi7 Udenko) 2 (Shikikai 7J): f3. '4 Techniques 1 and 4. Wandering: room 5,
Date of amendment order Showa year, month, day 8, l'-LaOF] on page 14, line 7 of the specification of amendment
” Japanese Patent Application Sho GO-17327 (9)

Claims (1)

[Claims] Light receiving means detects the afterglow of the light emitted from the charged and excited phosphor and converts it into an electrical signal, and integrates the received afterglow signal over a predetermined time period. an integrating means for calculating the integrated amount of afterglow light based on the phosphor, and an operation for calculating the temperature by comparing the obtained integrated amount of afterglow light with the temperature characteristic of the integral value of the afterglow amount set in advance according to the phosphor. The integrating means includes a V/F conversion circuit that converts the received afterglow electric signal into a pulse signal with a frequency corresponding to the magnitude thereof, and an output pulse of the V/F conversion circuit for converting the output pulse of the V/F conversion circuit into the predetermined time period. A temperature measuring device comprising: a counting means for counting over (2) The temperature measuring device according to claim (1), wherein the starting point of the integration time period is the point at which the excitation of the phosphor stops. (3) The temperature measurement device according to claim (1), wherein the temperature measurement device is determined based on the end point of the integration time period or the afterglow peak brightness of the phosphor that reaches the measurement upper limit temperature. (4) The temperature measuring device according to claim (1), wherein the end point of the integration time period is the point in time when the afterglow signal becomes equal to or less than a predetermined lower limit value. (5) The temperature measuring device 0 according to claim (1), in which the integration time period is fixedly set in advance. (6) The excitation of the phosphor is repeated multiple times, and the remaining time is The temperature measuring device according to claim 1, wherein the temperature is calculated at 17A using an average value or an added value of the integrated light amount.