JP2015059784A - Ozone concentration measurement apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ozone concentration measurement apparatus using a nitride-based deep ultraviolet semiconductor light-emitting element which maintains constant output and can perform stable and accurate measurement for a long time.SOLUTION: The ozone concentration measurement apparatus includes: chopping drive measurement means for measuring an ozone concentration while applying current to a solid light-emitting element 201 and fluctuating the current between an upper limit current value and a lower limit current value so as to obtain a constant ultraviolet radiation output value; and output maintenance correction means for correcting the upper limit current value and the lower limit current value so as to obtain a constant ultraviolet radiation output value when an ultraviolet radiation output value recorded in immediately prior ozone concentration measurement fluctuates. This allows for correct ozone concentration measurement.

Description

  The present invention relates to an ultraviolet absorption type ozone concentration measuring apparatus for measuring a solid light emitting element by chopper transmission.

According to Non-Patent Document 1, which is a reference book explaining ultraviolet rays, ozone has absorption bands called Chapuis band (850 nm to 440 nm), Huggins band (360 nm to 300 nm), and Hartley band (200 to 320 nm).

Around 1992, ozone concentration was measured by using a low-pressure mercury lamp instead of the conventional wet method. Unlike wet methods, low-pressure mercury lamps do not use chemicals, are easy to maintain, and have high measurement sensitivity, so the use of low-pressure mercury lamps for ozone concentration measurement has increased.

As shown in Patent Document 1, the ozone concentration measurement using a low-pressure mercury lamp uses ultraviolet light having a single wavelength of 254 nm emitted from a low-pressure mercury lamp using vacuum discharge.

The UV absorption type ozone concentration measurement measures the radiation output intensity I of the wavelength before being absorbed by ozone and the radiation output intensity O of the wavelength after being absorbed by ozone, and obtains the amount of absorbed ultraviolet rays. The principle that the ozone concentration at the wavelength is found from the above law is used.

Further, when the concentration is measured by the light absorption method, the sample to be measured can be obtained by the Lambert-Beer law formula 1 in both the gas phase and the liquid phase. The radiant output intensity of the transmitted light having the wavelength transmitted through the sample gas is O, the radiant output intensity of the incident light having the wavelength transmitted through the sample gas is I, the absorption coefficient of ozone at the wavelength is ε (the absorption coefficient of ozone is ε is The value of the ozone absorption coefficient is determined by each wavelength.), Where the ozone concentration in the sample gas or sample water is c, and the optical path length when the wavelength is transmitted through the sample gas or sample water is L, Equation 1 is It becomes as follows.

  However, when a low-pressure mercury lamp is used for ozone measurement, discharge noise of vacuum discharge appears as an error in the measured value, so correction that always removes the influence of noise is indispensable for the measured value. In addition, in the case of measuring ozone concentration at a low concentration, it is known that the measurement by reducing the output of the low-pressure mercury lamp makes it easier to perceive the attenuation of ultraviolet rays and can be measured with high accuracy.

In the case of low-concentration ozone, if the light source has a high output, ultraviolet rays are not absorbed by ozone, and light passes through ozone without being attenuated. This is also one of the factors that degrade measurement accuracy. On the other hand, if the output is low in the case of high-concentration ozone, all the light will be absorbed by ozone. The present invention relates to low-concentration ozone concentration measurement, and a weak output is suitable.

However, when the output is lowered to a weak level, no discharge occurs. Eventually, the mercury lamp needs an output that can be discharged and cannot be separated from the discharge noise. A low-pressure mercury lamp cannot be set to a weak output in principle and must be measured with increased output. This also has the problem that discharge noise always appears as a measurement error and cannot be measured correctly.

On the other hand, Patent Document 2 provides an ozone concentration measuring device that employs a nitride-based deep ultraviolet semiconductor light emitting element as a light source for measuring the ozone concentration. The intensity of ultraviolet rays emitted from this LED is weak.

  However, although the method of Patent Document 2 employs a nitride-based deep ultraviolet semiconductor light emitting device, it is possible to prevent a decrease in the intensity of the radiation output with the lapse of time of the LED only by the chopper transmission driving that blinks the device. However, since the output was weak, there was a problem that the lower limit of the measurable output was reached immediately. For this reason, it was not possible to adopt an ozone concentration measuring instrument using LED as a light source for ozone measurement in factories operating for 24 hours and uninhabited islands.

Patent Document 3 employs an optical chopper because the measurement accuracy can be increased by increasing the S / N ratio. However, a method that employs an LED as a light source has not been adopted. Since LEDs are capable of high-speed switching, they are excellent in terms of shortening the lightening period of the light source (increasing the lightening frequency), but LEDs generally have a small output (about several tens of μW) and are generated. It is estimated that the weak output of the LED cannot be used in the invention proposed by Patent Document 3 because the intensity of the light to be transmitted is small.

JP-A-5-172743 JP 2011-094970 A JP 2010-197310 A

Physical chemistry of the atmosphere Toshiaki Ogawa Publication place Tokyodo Publishing August 30, 1991

In order to solve the above problem, the inventors repeated trial and error by experiments. As a result, as measures to smooth the movement of electrons, a chopping technology that flashes a solid-state light emitting element that outputs ultraviolet rays at high speed before measurement, and a chopper transmission technology that increases and decreases the output in a rectangular wave shape while lighting during measurement. Immediately before the start of measurement, we adopted a technique such as flowing a constant current for a short time after heat dissipation by turning off the lights, and focused on the optimal combination of these procedures. In addition, we tried to improve the light receiving accuracy by removing measurement noise by applying the principle of the lock-in amplifier and stabilizing the measurement point at the top of the rectangular wave. Furthermore, the inventors have come up with a device for finely adjusting the current applied to the solid state light emitting device in order to keep the output attenuated with time constant. The object of the present invention is to control the decrease of the radiant output intensity of the solid state light emitting device with the passage of time, maintain a constant output even with a weak output (μW / cm 2), and stably stably for a long time. To provide an ozone concentration measuring device having a driving method capable of measuring.

  In order to solve the above problems, the present invention has the following features.

  The ozone concentration measuring apparatus according to the present invention uses, as a light source, a solid light-emitting element that emits ultraviolet light including a wavelength region of 200 nm to 320 nm. This apparatus comprises a chopping drive measuring means for measuring the ozone concentration while amplifying between the upper limit current value and the lower limit current value by applying a current to the solid state light emitting element to obtain a constant ultraviolet radiation output value, and the immediately preceding ozone concentration When the ultraviolet radiation output value recorded in the measurement is changed, it has an upper limit current value and an output maintaining correction means for correcting the lower limit current value so as to be a constant ultraviolet radiation output value.

  Although the ultraviolet radiation output value is the radiation intensity of ultraviolet radiation, in the present invention, it is regarded as a voltage value applied to an intensity sensor that has received radiation ultraviolet radiation. When a current is applied to the solid state light emitting device, ultraviolet rays are emitted. How much current is applied and how much ultraviolet light is emitted is based on the performance characteristics of the solid state light emitting device. The measurement of the radiation intensity is based on the performance characteristics of the intensity sensor and the device specifications. If the element or device is in an ideal state, the current value applied to the solid state light emitting element and the voltage value received by the light receiving intensity sensor show a constant correlation value, but there is a difference in the actual measurement environment. In addition, the output of a solid state light emitting device usually decreases as radiation continues. The voltage value received by the light-receiving intensity sensor varies depending on the aging of the devices and the description environment. For this measure, the voltage value received by the received light intensity sensor with respect to the current applied to the solid state light emitting element is set as a reference value in a fixed measurement environment. In other words, it is necessary to control to maintain the ultraviolet radiation output of the solid light emitting element constant while adjusting the current applied to the solid light emitting element. In the present invention, the means for executing this control is output maintaining correction means. In the embodiments, the solid state light emitting device is abbreviated as “light emitting device”.

  In an actual measurement environment, the current applied to the solid state light emitting element and the voltage value received by the light receiving intensity sensor are blurred each time measurement is performed. As described above, in addition to the apparatus characteristics, an ultraviolet light absorption action by ozone or the like exists in the measurement environment. In the present invention, the voltage value received by the received light intensity sensor is fixed, and this adjustment is performed by increasing / decreasing the current applied to the solid state light emitting device. This selection is also advantageous for a decrease in the output of the solid state light emitting device. The applied current to the solid state light emitting element has a range with respect to the voltage value received by the constant light intensity sensor, and the upper limit current value and the lower limit current value are used as threshold values for the measurement current. The voltage value received by the constant light intensity sensor is the above-described constant ultraviolet radiation output value.

  The fixed ultraviolet radiation output value is one, but the value may be an approximate value. Alternatively, the range can have a certain width. If there is a range in the fixed ultraviolet radiation output value, the applied current value to the solid state light emitting element naturally becomes wider. In extreme cases, it may be extended to a measurable limit, but it should be noted that the effect of the correction is diminished.

  It is an object of the present invention to suppress a decrease in output of a solid state light emitting device. Through experiments and trial and error, the inventors have found that a decrease in output of the solid state light emitting device can be suppressed by periodically amplifying the current applied to the solid state light emitting device between the upper limit current value and the lower limit current value. This driving method is also called chopping, but general chopping is blinking, and the present invention is different in that lighting is maintained. This is the chopping drive measuring means in the present invention. In the embodiment, “lighting type amplitude measurement” is used.

  The chopping drive measuring means of the present invention emits a rectangular wave having an upper limit current value as an upper vertex and a lower limit current value as a lower vertex without turning off ultraviolet rays from the solid state light emitting device, and measures the upper vertex and the lower vertex. It is characterized by being a point.

  If the periodic amplitude is a rectangular wave, the upper and lower vertices of the rectangular wave extend in time, which has the advantage that the measurement points can be easily grasped.

  The ultraviolet radiation output value is a voltage value obtained from the intensity sensor when ultraviolet light radiated from the solid state light emitting element is received by the measurement cell in a zero ozone state.

  In the present invention, the received light intensity is detected by one intensity sensor. The radiation intensity of the solid state light emitting device can be regarded as the intensity received by the intensity sensor if ultraviolet rays are not absorbed. Based on this principle, the present ozone concentration measuring device detects the value of the intensity sensor when the measurement cell is irradiated with ultraviolet rays in a zero gas state with a vacuum pump. When the sample cell is filled with the sample gas and emitted without changing the radiation intensity of the solid state light emitting device, the ultraviolet light is absorbed by ozone. Since the intensity sensor used at this time is the same as that measured in the zero gas state, the ozone concentration can be calculated from the Lambert-Beer law. The value obtained from the intensity sensor is a voltage value. The name of the ultraviolet radiation output value in the embodiment of the present invention is “zero gas reference value”, and the zero gas reference value obtained by ozone measurement is applied to the solid state light emitting device as the “zero gas reference value”, a constant ultraviolet radiation output value. The zero gas reference value that serves as an index for current correction is referred to as a “determined zero gas reference value”.

  In the output maintaining correction means, the correction current value for correcting the upper limit current value and the lower limit current value is extracted from a list prepared in advance according to the fluctuation value of the ultraviolet radiation output value.

  As described above, the radiation output of the solid state light emitting device tends to decrease through use. In order to compensate for this, the current applied to the solid state light emitting device is corrected. This correction current value depends on the performance characteristics and device characteristics of the solid-state light emitting element and the intensity sensor to be used. For this reason, it is practical to list the correction current values obtained in advance through experiments or the like according to the fluctuation value of the ultraviolet radiation output value, record it in a built-in memory of the microcomputer, and use it. However, the suitability of the list deteriorates due to the measurement environment and device characteristics. Therefore, it is desirable to automatically update using the measurement data under microcomputer control. In the present embodiment, the upper limit current value is referred to as “maximum lighting current value”, and the lower limit current value is referred to as “minimum lighting current value”.

  In the output maintenance correction means, the correction current value is adjusted according to the previous increase / decrease state of the ultraviolet radiation output value, and approaches a constant ultraviolet radiation output value for each continuous measurement.

  This method does not refer to the correction current value from the list for the fluctuation of the UV radiation output value obtained in the previous measurement, but the microcomputer calculates the appropriate value of the correction current value according to the difference. It is determined by processing. Since the measurement is performed continuously, if the previous correction current value is high, the current value is reduced this time, and the measurement is repeated until it gradually approaches a certain ultraviolet radiation output value. A list prepared in advance may be used to obtain the correction current value, but this is a correction function when an error occurs in the correction current value of the list. Even if the device does not have a list, correction can be performed by this function. Also, when the measurement environment does not match the list data, when the list becomes unusable due to device deterioration, or when the performance characteristics of the solid state light emitting device and the intensity sensor are far apart due to manufacturing differences Convenient to.

  Prior to the execution of the chopping drive measuring means, the solid state light emitting device is turned off for a time shorter than the execution time of the chopping drive measuring means, and then between the upper limit current value and the lower limit current value for a time shorter than the turn-off time. Is applied to drive the solid state light emitting device to idling.

  Turning off the light has an effect of radiating heat that causes a decrease in output from the solid state light emitting device. Further, applying a constant current value that is intermediate between the upper limit current value and the lower limit current value immediately before chopping driving has an effect of stabilizing the electronic state of the solid state light emitting device. This corresponds to idling driving. The appropriate length of time for extinguishing and constant current was obtained from the experimental results. These times depend on the device environment. In the present embodiment, this idling driving is referred to as “constant current driving”.

  After execution of the output maintaining correction means, the ultraviolet light from the solid state light emitting element is radiated with a periodic amplitude between the corrected upper limit current value and the current value zero value, and then corrected by the upper limit amplitude aging drive. The lower limit amplitude aging drive is performed, which is radiated with an amplitude periodically between the lower limit current value and the current value zero.

  When the output maintaining correction unit is executed, the current value applied to the solid state light emitting element is corrected. Since current values used for ozone measurement are different, aging is performed to adjust the electronic state of the solid state light emitting device again and stabilize it.

According to the present invention, even if the output is weak (μW / cm 2), it is possible to always obtain a constant radiation output intensity by correcting the current value applied to the element with respect to the decrease in the radiation output intensity.

The present invention activates the electronic state of the solid state light emitting device by performing aging before the measurement, and at the time of measurement, the electrons inside the solid state light emitting device repeat the excited state and the electron transfer by the rectangular wave chopper transmission that keeps lighting continuously Therefore, there is an effect of preventing a state where the output is unilaterally attenuated over time.

The present invention enables continuous measurement (24-hour continuous measurement) that was not possible with ozone concentration measurement using a solid-state light-emitting element as a light source by stabilizing the output by correcting the applied current value to the element and transmitting a rectangular wave chopper. It is.

Since the present invention employs rectangular wave chopper driving while having a weak output (μW / cm 2), the measurement point at the rectangular wave apex can be easily grasped and the number of measurement data samples can be increased. Highly accurate and stable measurement is possible.

It is a block diagram of the ultraviolet absorption type ozone concentration measuring apparatus using the directivity adjustment mechanism type chopper transmission system using the nitride system deep ultraviolet semiconductor light-emitting device which implements this invention. It is a block diagram of the directivity adjustment mechanism using the nitride type deep ultraviolet semiconductor light-emitting device which implements this invention. It is a transmission waveform using the nitride type deep ultraviolet semiconductor light emitting element by the chopper transmission system which implements this invention. FIG. 5 is a graph showing the relationship between the reference drive current value and the radiation output intensity from an experiment using the nitride-based deep ultraviolet semiconductor light emitting device used in the present invention. It is a schematic diagram of lighting type amplitude measurement of the present invention. It is a graph showing attenuation at the time of lighting type amplitude measurement and using a sine wave. The output intensity reduction correction and output stabilization means of the present invention are shown in a flowchart. It shows the state of output over time according to the present invention. It is a schematic diagram of blink type short period amplitude drive (maximum). It is a schematic diagram of blink type short period amplitude drive (minimum).

The present invention relates to an ultraviolet absorption ozone concentration measurement using ultraviolet rays in the Hartley band (200 to 320 nm). In the present invention, one intensity sensor 103 for detecting the received light intensity is used to detect the emission intensity before the ultraviolet light is absorbed by ozone (the radiant output intensity of the incident light (Lambert-Beer's law expressed in Equation 1) (I )) And the intensity of ultraviolet light absorbed by ozone (similarly, the radiant output intensity (O) of transmitted light) is detected. The radiant output intensity (I) of incident light is regarded as the radiant output intensity of incident light that is not affected by ozone because the voltage value detected by the intensity sensor 103 when the measurement cell 105 is in a zero gas state and irradiated with ultraviolet rays. And input to the microcomputer 114. This is the ozone zero reference value setting process. Since the ozone zero reference value is a radiation output intensity without absorption by ozone, it is desirable to always show a constant intensity. However, since the output of the light emitting element 201 varies with time (usually decreasing) as the light emitting element 201 continues to be used, the current value applied to the light emitting element 201 is adjusted based on the ozone zero reference value to make this intensity constant.

The reason why the light emission output of the element decreases with the lapse of time after the light emitting element 201 is turned on is that resistance is generated and heat is generated because the movement of electrons inside the element is not smooth. In the present invention, various experiments were conducted on the driving method of the light emitting element 201. As a result, it was found that when the current applied to the light emitting element 201 is periodically amplified, the output within a certain range can be maintained. This driving method was further experimented and devised, and was adopted as the output stabilization means of the present invention. This output stabilization means is realized by the light emitting element mechanism 118 controlling the driving of the light emitting element 201 in accordance with a command from the microcomputer 114.

The present invention is characterized by using a weak current as much as possible to drive the light emitting element 201 and measuring low-concentration ozone. However, when a weak current is used as described above, since the radiation intensity is weak, it cannot be measured in an ozone concentration environment where the irradiated ultraviolet rays are completely absorbed by ozone. Therefore, the ozone concentration measuring device of the present invention is premised on that the ozone concentration range to be measured is defined. Furthermore, the limit of the measurement capability is determined according to the performance of the utilization device such as the capability of the light emitting element 201 and the sensitivity of the intensity sensor 103 that receives light. As the light emitting element 201 continues to emit light, the radiation output usually changes gradually (usually decreases). In order to restore the radiation output, it is necessary to adjust the intensity of the current applied to the light emitting element 201. The output stabilizing means described above can be said to be a radiation output adjusting means for maintaining a constant radiation output. In order to be able to make adjustments, the equipment must be used in a marginal range, not at full capacity. As described above, the constant radiation output is not necessarily obtained from the constant current applied to the light emitting element 201, and the current intensity varies. That is, the current width that maintains a constant radiation output value becomes the threshold value of the measurement current. In the present invention, the upper limit of the threshold is called the maximum lighting current value 309 and the lower limit is called the minimum lighting current value 310. The intermediate value is referred to as a reference drive current value 311. As described above, since these values are based on the measurement equipment environment, in the present invention, the values are determined through experiments. In fact, see the examples.

The output stabilization means has two types of aging drive, a flashing short cycle amplitude drive (maximum) 301 and a flashing short cycle amplitude drive (minimum) 302, and a lighting type amplitude measurement 304 that measures absorbance as main functions. It operates under the control of the light emitting element mechanism 118. The blinking short cycle amplitude drive (maximum) 301 is an aging function that blinks between the maximum lighting current value 309 and zero current (lights off) at a constant cycle (sinusoidal). On the other hand, the blinking short cycle amplitude drive (minimum) 302 is an aging function that blinks between the minimum lighting current value 310 and the current zero (off) at a constant cycle (sinusoidal). The lighting type amplitude measurement 304 repeats a chopping cycle in a rectangular waveform at high speed between the thresholds of the measured current (between the maximum lighting current value 309 and the minimum lighting current value 310) while maintaining the lighting state, and at the maximum current and the minimum current. This is a function to obtain an ultraviolet absorption measurement value from both states. Further, before the lighting type amplitude measurement 304 is executed, the extinction (1) 306 and the constant current drive (2) 307 are executed in advance for both the zero gas measurement and the sample gas measurement. The light extinction (1) 306 has a role of calming the electronic state of the light emitting element 201 to dissipate heat. The constant current drive (2) 307 has a role of applying a current to the light emitting element 201 from a zero current state of extinguishing and making the current value constant when the reference drive current value 311 is reached. The combination of the turn-off and the constant current of the reference drive current value 311 is also a function that assists in stabilizing the output, is a part of the output stabilization means, and is controlled by the light emitting element mechanism 118.

Further, in the present invention, a radiation output value having no ozone absorption action is obtained by zero gas measurement, and then a radiation output value receiving ozone absorption action is obtained by sample gas measurement, and these two radiation output values are calculated by Lambert-Beer law. Based on this, the ozone concentration is calculated. This zero gas measurement and sample gas measurement are repeated twice to obtain a list of concentration data. Although measurement requires a long time, the output of the light emitting element 201 during measurement varies, and this variation must be suppressed. With respect to output fluctuation, the amount of current applied to the light emitting element 201 can be adjusted to maintain the output. In the present invention, the zero gas reference value (voltage value of the intensity sensor 103 at the time of light reception without absorption) obtained at the time of zero gas measurement is used as a reference value for maintaining output. That is, it is incorporated as a processing function of the output stabilization means. The zero gas reference value obtained at the first measurement is recorded as a fixed value, compared with the zero gas reference value for each measurement cycle, and the drive current value is adjusted so as to return to the fixed zero gas reference value. For this purpose, the “applied current amount for adjusting the radiation intensity of the light emitting element 201” was obtained by conducting an experiment in accordance with the performance characteristics of the measuring apparatus. The reduced output (usually reduced) is corrected based on the fixed zero gas reference value. This correction extends to the measurement current threshold and the reference drive current value 311 described above. In this way, the maximum lighting current value 309 and the minimum lighting current value 310 are also corrected, and a slight decrease in the output of the element can be returned to a constant value, and the light emitting element 201 has a stable radiation output intensity for a long time. Can be maintained. The “output adjustment function based on the zero gas reference value” described above is a core function of the output stabilization means, and is realized by the control of the microcomputer 114.

FIG. 7 is a flowchart showing an example in which ozone measurement is performed by combining and executing various drives constituting the output stabilization means of the present invention. 7 will be sequentially described.

S701 is an execution initial value extraction process. In measuring the ozone concentration, initial values and set values based on the measurement environment are taken out from the nonvolatile storage unit (not shown) of the microcomputer 114 and developed in the work area of the volatile storage unit (not shown). These include measurement time for measuring ozone concentration (for example, 1 hour), number of repetitions of setting zero gas reference value (for example, 10 times), number of measurement cycles for sample gas measurement (for example, 10 times), Predeterminable measurable threshold values (maximum lighting current value 309 (eg 9.1 mA) and minimum lighting current value 310 (eg 8.9 mA)) and reference drive current value 311 (eg 9.0 mA), vacuum pump An operating time (for example, 15 seconds) is set. In addition, the number of repetitions (the frequency of the sine wave) and the execution time when performing aging by the flashing short cycle amplitude drive (maximum) 301 and the flashing short cycle amplitude drive (minimum) 302, the extinction (1) 306, the extinction (2) The execution time of 308, constant current drive (1) 305, constant current drive (2) 307, the number of repetitions (frequency of the rectangular wave) in the lighting type amplitude measurement 304 and the execution time thereof are also stored in the nonvolatile storage unit of the microcomputer 114. May be set in advance as an operation value unique to the apparatus.

  It is checked whether the measurement cycle is the first time (S702). If it is the first time, the ozone zero reference value is not yet available, and there is no need to adjust it compared to the previous measurement result. The light emitting element 201 may be driven with a predetermined value such as the reference drive current value 311 of the light emitting element 201. Those processes are not executed, and the process goes to S704.

  S703 is an output adjustment function based on the zero gas reference value, and is a core function of the output stabilization means. In this process, the gas zero reference value acquired in the previous measurement is compared with the determined gas zero reference value, and the output fluctuation (decrease) of the light emitting element 201 is corrected to the original radiation output. This correction is realized by changing the reference drive current applied to 201 in accordance with the degree of decrease. Normally, the reference drive current is increased with respect to the lowered output, but the amount depends on the device performance characteristics as described above. The value is obtained in advance from experimental values. However, a method of increasing the fixed amount and increasing or decreasing the reference drive current value 311 according to the result of the next measurement may be used. As the current increases or decreases, the threshold (maximum / minimum current value) of the measured current is also corrected. These corrected reference drive current value 311 and threshold value are updated and stored in the work area. In this process, the definite gas zero reference value is a value acquired by the first measurement and is fixed as a subsequent comparison reference value. However, in some cases, it may be confirmed after several test measurements. Further, in the initial measurement, variable elements such as the reference drive current value 311 are designated in advance by the device performance characteristics, and are stored in the work area in the process of S710. Therefore, there is no update process for the reference drive current value 311 or the like.

The vacuum pump 107 is operated for a specified time, and the measurement cell 105 is brought into a zero gas state (S704).

In step S705, aging drive is executed. Aging has the effect of shaking the device and stabilizing the flow of electrons. In the present invention, chopping is performed between the maximum lighting current value 309 that is the upper limit of the threshold value of the measurement current that maintains a constant radiation output value and the minimum lighting current value 310 that is the lower limit between the current zero state. First, a current is applied to the light emitting element 201 in a sine wave shape having a maximum lighting current value 309 as an upper vertex and a current 0 value (light extinction) as a lower vertex, with the amplitude periodically repeating. The light emitting element 201 repeats light emission and extinction due to the current at the upper limit of the threshold value of the measurement current, and the electronic state of the element is shaken. As the execution time and frequency, the values initially set in S701 are used. A rectangular wave (pseudo sine wave) may be used instead of the sine wave. This driving is called blinking short period amplitude driving (maximum) 301.
When the aging of the maximum current is completed, aging called flashing short period amplitude drive (minimum) 302 is executed. The operation specifications are the same except that the lower limit of the threshold value and the current 0 are set as the apexes.

FIG. 9 is a schematic diagram of flashing short period amplitude driving (maximum). The state in which the maximum lighting current value (maximum lighting) and the extinction are repeated and the light intensity is amplified is schematically shown. Flashing short-period amplitude drive (maximum) is a current that flows to the element by applying a load to the element by repeatedly amplifying the current value applied to the element to 0 mA (LED off) and the maximum lighting current value (LED maximum lighting) in a short period. The purpose is to stabilize.

FIG. 10 is a schematic diagram of blinking short cycle amplitude driving (minimum). The flashing short cycle amplitude drive (minimum) turns off the element and performs the minimum lighting current value (LED minimum lighting). The purpose is the same as the flashing short cycle amplitude drive (maximum) described above, by applying a load to the element. The purpose is to stabilize the current flowing through the element.

  Returning to FIG. S706 to S711 are steps for determining a zero gas reference value, and form means for zero gas measurement. The number of times designated in the initial processing of S701 is repeated. One zero gas reference value is determined from a plurality of acquired zero gas reference values. The determination method may be an average value or a standard deviation. Also, a specific value or the most frequent value may be selected.

Prior to zero gas measurement, the light emitting element 201 is turned off (1) 306 to calm the element's electronic state and release heat. This function assists the stabilization of output. The turn-off time depends on the designated time in S701 (S707).

A current is applied to the light-emitting element 201 from a static electronic state in which the extinguishing current is zero. When the reference drive current value 311 is reached, the current value is kept constant. This is the constant current drive (2) 307, which is a function that assists in stabilizing the output. The duration depends on the designated time in S701 (S708).

S709 is a step of acquiring the received light intensity of ultraviolet irradiation as a voltage value in the measurement cell 105 in a state of zero ozone. The measuring method of the lighting type amplitude measurement 304 is taken. The lighting type amplitude measurement 304 repeats a chopping cycle between the measured current threshold values (between the maximum lighting current value 309 and the minimum lighting current value 310) in a rectangular waveform at high speed while maintaining the lighting state. Sometimes an ultraviolet absorbance measurement is obtained. This value is recorded. The measurement time and frequency in this step are specified in S701.

FIG. 5 is a schematic diagram of a light emitting rectangular wave in the lighting type amplitude measurement 304. A current is applied to the light emitting element 201 in the form of a rectangular wave for a certain period of time with the maximum lighting current value 309 as the top vertex and the minimum lighting current value 310 as the bottom vertex. It has the feature of chopping while turning on without turning off. It is a chopper transmission while turning on the light, which was not possible with the conventional rotating disk type mechanical method. Since the light is turned on, the rise of the light intensity becomes smooth and the intensity can be stabilized.Especially in the case of micro ozone measurement, even when the difference between the voltage values of the zero gas state and the sample gas state is slight, The minimum lighting current value 310 can detect a minute change.

  Returning to FIG. The measurement data is recorded in a recording device (not shown) under the control of the microcomputer 114. The measurement data may be brought into the analysis process as it is. Further, significant data may be selected and given as a measured value (S710).

  S712 is a step of determining whether or not the measurement has been normally performed. Since it is a process for reducing ozone to zero, the measured value should show almost the same value after a certain period of time. Therefore, it can be regarded as abnormal when the variation in measurement data is severe or when a constant value does not continue. If an abnormality occurs, the measurement is stopped and the abnormal end is notified (S713).

  When zero gas measurement is completed normally, an appropriate measurement value is selected using a statistical method or the like. This value is the zero gas reference value. This value is stored and saved in the work area (S714) for use in output correction (S703) of the light emitting element 201 in the next measurement.

  It is determined whether the zero gas measurement is the first time. If it is the first time, it is necessary to set a fixed zero gas reference value (S715). If this is the first time, go to S710.

  Since this is the first measurement, the zero gas reference value is a fixed zero gas reference value. The zero gas reference value is stored and saved in the work area as a confirmed zero gas reference value (S716).

While the vacuum pump 107 is driven, the electromagnetic valve 106 is opened, and the sample gas is allowed to flow into the measurement cell 105 from the sample gas inlet side 108. The switching time from the zero gas state to the sample gas state in the measurement cell 105 is specified by the initial setting (S717).

  S718 to S723 are steps for measuring the light receiving intensity of the sample gas for measuring the ozone concentration, and form means for measuring the sample gas. The number of sample gas measurement values acquired is recorded by repeating the number of times designated in the initial processing of S701. When determining one measurement value, an average value or a standard deviation may be applied. Also, a specific value or the most frequent value may be selected. The acquired data and the measured ozone concentration are left to the intention of the application field of the ozone concentration measuring apparatus according to the present invention. Further, before performing the sample gas measurement, the light emission in S719, the constant current drive in S720, the lighting type amplitude measurement 304 in S721, and the processing in S722 have the same specifications as the zero gas measurement step.

  S724 is a step of determining whether the measurement has been normally performed. Even the sample gas should show almost the same measured value. Therefore, it can be regarded as abnormal when the variation in measurement data is severe or when a constant value does not continue. However, when the value is the same as the ozone zero value, there is a possibility that the ozone is actually zero. Also, when the ozone concentration is too high and all ultraviolet rays are absorbed, it is also determined as abnormal. In addition, if there is a lot of abnormal value data in the minimum lighting current value 310 in the lower limit value of the measured current threshold value, it can be considered that the ozone concentration is too low, or the system failure that the threshold value setting is not successful. to decide. If an abnormality occurs, the measurement is stopped and the abnormal end is notified (S725).

  In S726, the end of the measurement cycle is determined. If the measurement time has not ended, measurement is performed again (S727).

The present invention is characterized in that the direction of ultraviolet rays emitted from the light emitting element 201 is adjusted, and a decrease in the radiant output intensity of the light emitting element 201 with the passage of time can be suppressed indirectly.

The light emitting element 201 is not assembled while the element is turned on and the direction of ultraviolet irradiation is confirmed. For this reason, the assembly with only mechanical accuracy cannot control the direction of irradiation of ultraviolet rays, and the apparatus is irradiated to affect the deterioration.

In order to control the direction of the ultraviolet rays of the light emitting element 201, LED manufacturers have attached lenses to the elements for sale, and the catalog can irradiate ultraviolet rays such as parallel light (± 6 degrees) and dispersed light with a certain accuracy. There is a description that can be done, and by attaching a lens, the direction of ultraviolet rays is controlled and sold.

However, even a slight deviation in the direction of light is not controlled, and the irradiated ultraviolet light appears as a difference in radiant output intensity between the central portion and the outer peripheral portion when, for example, a parallel lens is used. In addition, the light is not incident on the parallel lens at a right angle, and the deviation of the incident angle does not exhibit the performance of the parallel lens, the light is not converted into parallel light, and the light passing through the lens is shifted, All light does not enter the measurement cell, and the leaked light is irradiated to the apparatus.

As a result, the intensity sensor is not irradiated with ultraviolet rays due to the deviation in the direction of light, and appears as a decrease in the radiation output intensity, and the current value applied to the light emitting element 201 is increased.

As a result, the current value that does not need to be applied to the light emitting element 201 is increased, leading to element damage, the performance of the element deteriorates, and the radiation output intensity decreases with time. It was connected.

According to the present invention, after the light emitted from the light-emitting element 201 is converted to ultraviolet light having a single wavelength by the optical filter, the direction of the ultraviolet light is adjusted in the horizontal direction and the vertical direction.

The present invention is a method for adjusting the direction of ultraviolet rays with a directivity adjustment jig in the left-right direction, the up-down direction, and the front-rear direction, but using a commercially available manual stage guide, the tilt direction, the rotation direction, and the multi-axis direction The direction of light may be adjusted by combining the linear motion directions. A fine adjustment method is generally used with a micrometer head, but a fine pitch screw may be used.

Moreover, the focus is shifted without adopting the design focus focus distance (focal distance) of the parallel lens described in a commercially available catalog (the focus is shifted in the direction in which the LED and the parallel lens are brought closer). ing. Ultraviolet rays do not become completely parallel light, but take advantage of the fact that ultraviolet rays spread slightly.

The focus shifting method results in light dispersion, and it is possible to avoid a single point concentration of light irradiated to the intensity sensor and to prevent deterioration of the intensity sensor. As a result, there is an effect of suppressing a decrease in radiation output intensity with the passage of time of ultraviolet rays emitted from the light emitting element 201.

When using a synthetic quartz plano-convex lens (PCX) focal length of 40 mm (model number 48818-L) commercially available from Edmund Optics Japan, it is appropriate to set the focal length to 26 mm based on the results of experiments. ing.

  FIG. 1 is a configuration diagram of an ultraviolet absorption ozone concentration meter 1 by an output stabilization means using a light emitting element 201 of a light emitting element box 101. An outline of the configuration diagram will be described with reference to FIG. First, set the zero ozone reference value. The ozone zero reference value can be set with a commercially available zero gas generator. By removing ozone gas with a catalyst (palladium catalyst, activated carbon, etc.) and an adsorbent, it is possible to create a zero ozone state. The present invention employs a vacuum pump type. The light emitting element 201 of the light emitting element box 101 is turned off so that light is not irradiated. The electromagnetic valve 106 is closed so that the sample gas does not flow into the measurement cell 105. The vacuum pump 107 is actuated to evacuate oxygen, ozone, gas contained in the atmosphere, minute moisture, minute matter, etc. from the exhaust gas outlet 111 to create a vacuum state. There is also an object to initialize the performance of the parallel lens 110 and the intensity sensor 103 according to the measurement environment (temperature, humidity) of ozone concentration by evacuating the measurement cell 105. The intensity sensor 103 is an ultraviolet sensor device. When the intensity sensor 103 is not irradiated with light, the voltage value of the intensity sensor 103 passes through the amplifier 104 and is input to the microcomputer 114 via the interface 113 as a zero value.

  When the exhaust of the measurement cell 105 is finished and the vacuum state is reached, the light emitting element 201 of the light emitting element box 101 is driven in the measurement cell 105 by the above-described output stabilizing means while the vacuum pump 107 is operated. Measurement is performed by lighting type amplitude measurement (S709). The light travels in the irradiation direction 112, and the ultraviolet light having a continuous wavelength travels while being converged in the ultraviolet constraining tube mechanism 117 (which can be filled with an inert gas or a vacuum), and the irradiation spot diameter becomes small and is irradiated to the optical filter 202. The continuous wavelength is narrowed down to a single wavelength by the optical filter 202, proceeds in the light emitting element box 101 (gas filling or vacuum is possible), passes through the parallel lens 110 attached to the parallel lens mounting mechanism 102, and enters the measurement cell 105. Incident. Since the measurement cell 105 is in a vacuum state, a single wavelength that has become parallel light is not absorbed by ozone and the radiation output intensity is not attenuated. The intensity sensor 103 measures the radiation output intensity. The value measured by the intensity sensor 103 is output as a voltage value, and the radiation output intensity of incident light is I. This voltage value is input to the microcomputer 114. I = radiant output intensity of incident light (ozone zero reference value), and setting of the ozone zero reference value is completed.

  After setting the ozone zero reference value, measure the sample gas. The electromagnetic valve 106 is opened while the vacuum pump 107 is operated, and the sample gas flows into the measurement cell 105 from the sample gas inlet side 108. By adjusting a valve attached to the flow meter 109 to adjust the flow rate of the sample gas flowing into the measurement cell 105 to a minimum, the measurement cell 105 can be kept in a vacuum. With the sample gas flowing into the measurement cell 105, the light-emitting element 201 is driven by the output stabilization means to perform lighting-type amplitude measurement (S721). The light absorbed by ozone contained in the sample gas and attenuated is incident on the intensity sensor 103, and becomes the radiant output intensity of the transmitted light. The value measured by the intensity sensor 103 is output as a voltage value. The radiated output intensity of the transmitted light is O, and this voltage value is input to the microcomputer 114. Let O = radiant output intensity of transmitted light.

  When the incident light radiant output intensity (zero ozone reference value) I and the transmitted light radiant output intensity O are input to the microcomputer 114, the microcomputer 114 calculates the ozone concentration by calculating from Lambert-Beer's law, Equation 1. Is calculated. The value calculated by the microcomputer 114 is displayed on the display 115. For example, values to be displayed are processed by the microcomputer 114 such as the maximum value, minimum value, average value, standard deviation, and displayed on the display 115.

  FIG. 2 is a configuration diagram of the directivity adjusting mechanism 200 of the light emitting element 201 attached to the adjusting mechanism mounting base 203 and the optical filter 202 (single wavelength extraction filter) attached to the ultraviolet constraining tube mechanism 212. A continuous wavelength of 200 to 320 nm is irradiated from the light emitting element 201, passes through the ultraviolet constraining tube mechanism 212, and is narrowed down to a single wavelength by the optical filter 202 (single wavelength extraction filter). The ultraviolet restriction tube mechanism 212 between the light emitting element 201 and the optical filter 202 is processed into a cylindrical shape, and the optical filter 202 is irradiated with the direction of the ultraviolet light 119 emitted from the light emitting element 201 within a predetermined range. The surface of the light-emitting element 201 and the surface of the optical filter 202 can be obtained because the active oxygen O due to the continuous wavelength emitted by filling the ultraviolet constraining tube mechanism 117 (material metal, glass, ceramics) with an inert gas (even in a vacuum state) is not generated. It is also possible to prevent the formation of an oxide film. The ultraviolet ray 119 that has passed through the optical filter 202 is directed by the directivity adjusting mechanism 200 so that the central portion of the parallel lens 110 is irradiated with the ultraviolet ray 119. This makes it possible to fine-tune the left and right direction of the light. The ultraviolet vertical adjustment direction 208 is adjusted by the vertical rotation pin 207 attached to the vertical adjustment guide 206 and fixed by the vertical fixing pin 211. The ultraviolet light left / right adjustment direction 209 is adjusted by the left / right rotation pin 204 attached to the fixing base 205 and fixed by the left / right fixing pin 210. In the light emitting element box 101, a focus adjustment guide 116 is a fixed base, and the focus value is shifted in the focus adjustment groove 119 in the ultraviolet front-rear adjustment direction 121 with respect to the parallel lens 110 from the focus value of the catalog publication value. The directivity adjustment mechanism 200 is set at a predetermined position and fixed to the focus adjustment guide 116 with the focus fixing screw 120. The shift of the focus value results in a shift of the focus of the ultraviolet rays, and it is possible to measure by dispersing the light uniformly in the measurement cell and absorbing the ultraviolet rays in ozone, and the ultraviolet rays to the parallel lens 110, the measurement cell 105, and the intensity sensor. It is possible to prevent the deterioration of equipment due to the lack of concentration of one point.

The optical filter 202 can extract a single wavelength of 214 nm to 296.5 nm (0.5 nm span). Note that the method of filling the entire light emitting element box 101 with an inert gas (even in a vacuum state) and entering the ultraviolet light restricting tube mechanism 117 eliminates active oxygen O so that the apparatus is not damaged. In addition, in order to prevent the cleaning failure of the light emitting element mechanism 118 and the mixing of foreign matter, the light emitting element mechanism 118 is installed outside the light emitting element box 101, so that the inside of the light emitting element box 101 and the inside of the ultraviolet light restricting tube mechanism 212 can be stabilized. And the degree of vacuum can be maintained.

An example of the output stabilization means of the present invention is shown below. The ultraviolet ray emitted from the light emitting element 201 gives an error to the measurement value and causes re-ozonization. The ozone absorption wavelength (255 nm) is removed, and the ultraviolet ray near the central value of the Hartley band (near the central value of 200 to 320 nm) is used. Some 265 nm was adopted.

FIG. 3 shows an example of the output stabilization means of the present invention. Flashing short cycle amplitude drive (maximum) 301 → Flashing short cycle amplitude drive (minimum) 302 → constant current drive (1) 305 → lock-in drive 303 → light-off (1) 306 → constant current drive (2) 307 → lighting When the light emitting element 201 that emits a continuous wavelength of 200 to 320 nm of the light emitting element mechanism 118 is driven by the expression amplitude measurement 304 → light-off (2) 308, the value of the intensity sensor 103 is expressed as a voltage value on the vertical axis. It is a screen. The light emitting element 201 emits a continuous wavelength having a peak wavelength of 265 nm. The vertical axis of the upper and lower graphs represents the voltage value of the intensity sensor 103 and is “2 V / span”, and the lower graph is an enlargement of the lock-in drive 303, the lighting type amplitude measurement 304, etc. of the upper graph. Is. The upper horizontal axis time is “100 mS / span”, and the lower horizontal axis time is “5 mS / span”. For example, the total time from the lower constant current drive 1305 to the lock-in drive 303 is 15 mS.

As an example of the present invention, lock-in driving (driving time≈10 mS, frequency≈1 KHz) is adopted as the output stabilizing means. By applying a sine wave to the reference drive current value and amplifying it within the range of the maximum lighting current value 309 and the minimum lighting current value 310, it is possible to correct the phase of the drive circuit, and to eliminate noise generated from the pump and solenoid valve. In 114, the principle of the lock-in amplifier (a minute signal buried in noise can be detected with high sensitivity) is processed. The output reduction of the element can be prevented by the optimization condition of the lock-in drive. The relationship between the lock-in drive and the output reduction of the element will be clarified in further studies.

In FIG. 3, the minimum lighting current value 310 of the blinking short cycle amplitude driving (minimum) 302 is decreased by “1 V” and the reference driving current value 311 is decreased by “0.5 V” in the lighting type amplitude measurement 304. We plan to find the optimum value in future experiments.

The blinking short cycle amplitude drive (maximum) 301 is set to blink time≈250 mS, radiation output intensity at amplitude≈0.19415 μW / cm 2, lighting time≈0.25 S / 2 (flash frequency≈48 to 52 Hz). The current value is changed with a sine waveform to amplify the light intensity.

The blinking short cycle amplitude drive (minimum) 302 is set to blink time≈220 mS, radiation output intensity at amplitude≈0.19238 μW / cm 2, lighting time≈0.22 S / 2 (flashing frequency≈55 to 60 Hz). The current value is changed with a sine waveform to amplify the light intensity.

The constant current drive (1) 305 has a lighting time ≈ 5 mS and a drive time of the lock-in drive 303 ≈ 10 mS (frequency ≈ 1 KHz).

The extinguishing time (1) 306 is set to the extinguishing time≈8 mS.

Driving time of constant current driving (2) 307 is set to approximately 5 mS.

The lighting type amplitude measurement 304 is lighting time≈10 mS (frequency≈1 KHz).
The maximum lighting current value is 309≈9.770742 mA (radiant output intensity≈0.19415 μW / cm 2). The minimum lighting current value is 310≈9.61914 mA (radiant output intensity≈0.19238 μW / cm 2).

The extinguishing time (2) 308 is set so that the extinguishing time is approximately 500 ms.

  FIG. 4 is a graph in which the radiation output intensity is measured by radiating a wavelength of 255 to 285 nm (peak wavelength: 265 nm) using the light emitting element 201 embodying the present invention. Ultraviolet radiation output intensity was measured with a spectroscope at the Tokyo Metropolitan Industrial Technology Research Center. (Specification Prism grating method Measurement wavelength 200 nm to 2500 nm Spectrometer Co., Ltd. Model No. US-25ART) The vertical axis represents the radiation output intensity value, and the horizontal axis represents the wavelength emitted from the light emitting element 102. Radiant output intensity with respect to a reference drive current value of 1 mA (401), 5 mA (402), and 9 mA (403) at a peak wavelength of 265 nm (manufactured by DOWA Electronics Co., Ltd.) is 0.001 (μW / cm 2 · 265 nm), 0.075 (ΜW / cm 2 · 265 nm) and 0.18 (μW / cm 2 · 265 nm) can be read.

FIG. 6 is a graph showing attenuation when a sine wave is used as an example for the lighting type amplitude measurement (304). The vertical axis represents the voltage value of the intensity sensor, and the horizontal axis represents time. This represents a state where ozone is irradiated with light and attenuated. From the top of the graph, the ozone concentrations are 0 ppm (601), 0.1 ppm (602), 0.2 ppm (603), and 0.3 ppm (604). For example, by checking the voltage value of the full width at half maximum (FWHM) of the sine wave when ozone is present and the attenuation value of the voltage value of the full width at half maximum of the sine wave without ozone (zero gas state) Concentration can be measured. The voltage value of the full width at half maximum with an ozone concentration of 0 ppm (601) is 2.5 V, and the voltage value of the full width at half maximum with an ozone concentration of 0.2 ppm (603) is 1 V. In the measurement of the sine wave, the time of the horizontal axis of the full width at half maximum with an ozone concentration of 0 ppm (601) is different from the time of the full width at half maximum of an ozone concentration of 0.2 ppm (603), and the ozone concentration is 0 ppm and 0. The measurement time is different at 2ppm. In order to make the measurement times coincide with each other by using a sine wave, only the vertex of the sine wave is used, and the single point measurement of the vertex decreases the reliability of the measurement accuracy. Since the measurement of the present invention employs a rectangular wave, there is no time axis deviation at the time of attenuation.

FIG. 8 shows a state in which the output of the measurement cell 105 is reduced with the passage of time according to the present invention when the inside of the measurement cell 105 is in a zero gas state. The vertical axis represents the voltage value of the intensity sensor 103. The horizontal axis is the elapsed time. It can be seen that there is no decrease in the voltage value (output decrease) of the intensity sensor 103 with the passage of time in the zero gas state by the output stabilization means 801 according to the present invention. On the other hand, in the continuous lighting 802 with a constant current, it can be seen that the voltage value of the intensity sensor 103 decreases by 47.2% about 40 minutes after the lighting. (Output drops from 1.8V to 0.85V.)

  The configuration of FIG. 1 can also be applied to an ozone concentration measuring device in solution (liquid phase).

DESCRIPTION OF SYMBOLS 1 UV absorption type ozone concentration meter 101 by chopper transmission method Light emitting element box 102 Parallel lens mounting mechanism 103 Intensity sensor 104 Amplifier 105 Measurement cell 106 Electromagnetic valve 107 Vacuum pump 108 Sample gas inlet 109 Flow meter 110 Parallel lens 111 Exhaust gas outlet 112 Irradiation Direction 113 Interface 114 Microcomputer 115 Display 116 Focus adjustment guide 117 Ultraviolet constraining tube mechanism 118 Light emitting element mechanism 119 Focus adjustment groove 120 Focus fixing screw 121 Ultraviolet front and rear adjustment direction 200 Directivity adjustment mechanism 201 Light emitting element 202 Optical filter 203 Adjustment mechanism removal Attached base 204 Left / right rotation pin 205 Fixing base 206 Up / down adjustment guide 207 Up / down rotation pin 208 UV up / down adjustment direction 209 UV left / right adjustment direction 210 Pin 211 vertical fixing pin 212 focus adjustment fixing hole 301 flashing type short period amplitude drive (maximum)
302 Flashing short period amplitude drive (minimum)
303 Lock-in drive 304 Lighting type amplitude measurement 305 Constant current drive (1)
306 Off (1)
307 Constant current drive (2)
308 OFF (2)
309 Maximum lighting current value 310 Minimum lighting current value 311 Reference drive current value 401 Reference drive current value 1 mA
402 Reference drive current value 5 mA
403 Reference drive current value 9 mA
601 0ppm
602 0.1ppm
603 0.2ppm
604 0.3ppm
801 Output stabilization means 802 Continuous lighting

Claims (7)

An ozone concentration measuring apparatus using a solid light-emitting element that emits ultraviolet light including a wavelength region of 200 nm to 320 nm as a light source,
Chopping drive measuring means for measuring the ozone concentration while amplifying between the upper limit current value and the lower limit current value by applying a current to the solid state light emitting element to obtain a constant ultraviolet radiation output value;
Output maintaining correction means for correcting the upper limit current value and the lower limit current value so as to be the constant ultraviolet radiation output value when the ultraviolet radiation output value recorded in the previous ozone concentration measurement fluctuates;
An ozone concentration measuring apparatus characterized by comprising:   The chopping drive measurement means radiates the upper limit current value and the lower apex without emitting the ultraviolet rays from the solid state light emitting element so that the upper limit current value is radiated in a rectangular wave shape having the upper limit current value and the lower limit current value being the lower apex. The ozone concentration measuring device according to claim 1, wherein   3. The ozone concentration measuring apparatus according to claim 1, wherein the ultraviolet radiation output value is a voltage value obtained from an intensity sensor when ultraviolet light radiated from the solid state light emitting device is received by a measurement cell in a zero ozone state.   4. The output maintaining correction means, wherein the correction current value for correcting the upper limit current value and the lower limit current value is extracted from a list prepared in advance according to a fluctuation value of the ultraviolet radiation output value. The ozone concentration measuring apparatus according to claim 1.   5. The output maintaining correction unit adjusts the correction current value according to an increase / decrease state of the previous ultraviolet radiation output value, and approaches the constant ultraviolet radiation output value for each continuous measurement. The ozone concentration measuring apparatus according to claim 1.   Prior to the execution of the chopping drive measuring means, the solid-state light emitting element is turned off for a time shorter than the execution time of the chopping drive measuring means, and then the upper limit current value and the lower limit for a time shorter than the turn-off time. The ozone concentration measuring apparatus according to any one of claims 1 to 5, wherein an idling drive of the solid state light emitting element is performed by applying an intermediate current value. After execution of the output maintaining correction means, ultraviolet rays from the solid state light emitting element are
An upper limit amplitude aging drive that is radiated with periodic amplitude between the corrected upper limit current value and the current value zero value;
Next, a lower limit amplitude aging drive that is radiated with periodic amplitude between the corrected lower limit current value and the current value zero value,
The ozone concentration measuring device according to any one of claims 1 to 6, wherein: