JP2017227590A - Ozone concentration control system and zero point correction method for semiconductor type ozone sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ozone concentration control system capable of accurately controlling ozone concentration in a processing space using an ozone concentration meter mounted with a semiconductor type ozone sensor and a zero point correction method, for the semiconductor type ozone sensor, capable of improving detection accuracy of the ozone concentration.SOLUTION: In an ozone concentration control system which maintains ozone concentration in a processing space at target ozone concentration on the basis of output of an ozone concentration meter mounted with a semiconductor type ozone sensor, a control device: drives the semiconductor type ozone sensor in a manner that periodically repeats an ozone concentration measurement period and a refresh period; and executes a zero point correction process which renews a reference output value in a manner that replaces the previous reference output value corresponding to a predetermined target ozone concentration with a sum of the same and a variation of an output value obtained through the semiconductor type ozone sensor with respect to a zero output value set for the semiconductor type ozone sensor at a start time of the ozone concentration measurement period after completion of the refresh period.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an ozone concentration control system and a zero point correction method for a semiconductor ozone sensor used in the ozone concentration control system.

  Ozone having a strong oxidizing power is used in various fields for the purpose of processing such as sterilization, deodorization, decolorization, organic substance removal, harmful substance decomposition and removal, and chemical substance synthesis. The ozone used for each application has an optimum concentration range depending on the application. For this reason, when the above processing is performed spatially, it is desirable to control the ozone concentration in the processing space to a predetermined level.

In general, the ozone concentration is measured by an ultraviolet absorption method (absorbance method). Ozone absorbs ultraviolet light having a wavelength of around 254 nm. Therefore, a sample gas is introduced into a sample cell having a constant optical path length, and the sample gas is irradiated with ultraviolet rays in the wavelength range (near 254 nm), and the ozone concentration is quantified by the absorbance at that time.
The ultraviolet absorption method can stably measure the ozone concentration. However, since a sample cell, an ultraviolet light source that emits light including ultraviolet light having a wavelength of 254 nm, an ultraviolet intensity monitor for measuring absorbance, and the like are required, an ozone densitometer becomes relatively large.

Accordingly, the inventors focused on a semiconductor sensor having a relatively simple structure and a small size, and tried to employ the semiconductor sensor for ozone concentration measurement.
Since the structure and principle of the semiconductor sensor are described in, for example, Patent Document 1 and Patent Document 2, detailed description is omitted, but the operation is as follows.
The semiconductor sensor has a gas sensitive part made of a metal oxide semiconductor material such as tin oxide (SnO ₂ ), and a heater for heating the gas sensitive part. Usually, when the surface of the metal oxide semiconductor material constituting the gas sensitive part is in a clean atmosphere, oxygen in the atmosphere is adsorbed. In this state, oxygen on the surface is captured by oxygen, and as a result, the resistance value of the metal oxide semiconductor material is increased.

  Here, consider a case where the detection gas is a reducing gas such as CO. When the detection gas reaches the surface of the metal oxide semiconductor material constituting the gas sensitive part, an oxidation-reduction reaction occurs between the reducing detection gas and oxygen adsorbed on the surface. As a result, oxygen on the surface is separated from the surface, and electrons captured by the oxygen are free to move in the metal oxide semiconductor material. That is, the resistance value of the metal oxide semiconductor material is low.

  When such a semiconductor sensor is used to detect an oxidizing gas such as ozone, when the ozone gas reaches the surface of the metal oxide semiconductor material constituting the gas sensitive part, the surface is oxidized by ozone, and the surface Increases the amount of oxygen adsorbed on. As a result, the amount of electrons captured on the surface by oxygen increases, and as a result, the resistance value of the metal oxide semiconductor material increases.

JP 2005-257702 A JP 2014-035267 A

FIG. 3 is a diagram showing output characteristics of an ozone concentration meter using an ultraviolet absorption method (absorbance method) and output characteristics of an ozone concentration meter equipped with a semiconductor sensor. These output characteristics are obtained, for example, by performing ozone concentration measurement in a state where the ozone concentration in the processing space is maintained at a substantially constant value (for example, 0.5 ppm). In addition, after a predetermined time elapsed from the start of the ozone concentration measurement (for example, after 9000 seconds have elapsed), ozone in the processing space was exhausted, and the ozone concentration measurement was continued even after exhausting the processing space.
A curve (a) in FIG. 3 is an output characteristic curve of an ozone concentration meter using an ultraviolet absorption method (absorbance method), and a curve (b) is an output characteristic curve of an ozone concentration meter provided with a semiconductor sensor. . Curve (c) shows the change in humidity over time in the processing space.

As is apparent from FIG. 3, in the ozone concentration meter using the ultraviolet absorption method, the ozone concentration in the processing space can be stably measured, and the ozone in the processing chamber after exhausting the processing space. The concentration value indicates “0 ppm”.
On the other hand, in the ozone concentration meter provided with the semiconductor type sensor, it was confirmed that the output of the semiconductor type sensor gradually drifted with the ozone exposure time or was affected by humidity. Further, the ozone concentration value in the processing chamber after exhausting the processing space did not show “0 ppm”, but showed a concentration value drifted to some extent. Although the cause of such a phenomenon is not necessarily clear, it is considered that the influence of the adsorbed gas adsorbed on the surface of the metal semiconductor material constituting the gas sensitive part is also partly involved.

  As described above, in an ozone concentration meter equipped with a semiconductor sensor, since the sensor output value is significantly drifted by being exposed to the ozone atmosphere for a certain period of time or more, it is not suitable as an ozone concentration meter in an ozone concentration control system. It turns out that.

The present invention has been made based on the above circumstances, and measures the ozone concentration in the processing space with a certain accuracy in a configuration using an ozone concentration meter equipped with a semiconductor type ozone sensor. An object of the present invention is to provide an ozone concentration control system that can control the ozone concentration in the processing space with high accuracy.
In addition, the present invention provides a zero output correction method for a semiconductor ozone sensor that can compensate for fluctuations in sensor output caused by exposure to an ozone atmosphere for a certain period of time and improve ozone concentration detection accuracy. The purpose is to do.

The ozone concentration control system of the present invention comprises a semiconductor ozone sensor, an ozone concentration meter for measuring the ozone concentration in the processing space,
An ozone generator for releasing ozone into the processing space;
The semiconductor ozone sensor is driven so that an ozone concentration measurement period in which the heater in the semiconductor ozone sensor is in an operating state and a refresh period in which the heater is in a resting state are periodically repeated, and the semiconductor ozone sensor A control device for controlling the ozone generator so that the processing space is maintained at a set target ozone concentration based on an ozone concentration measured by a sensor;
In the control device, an output value for the semiconductor ozone sensor according to the target ozone concentration is set as a reference output value (A),
The variation (Ad) of the output value obtained by the semiconductor ozone sensor at the start of the ozone concentration measurement period after the refresh period of the semiconductor ozone sensor with respect to the zero output value set for the semiconductor ozone sensor A zero point correction process is performed in which the sum of the reference output value (A) is updated and set as a new reference output value (A + Ad).

  In the ozone concentration control system of the present invention, when the operation of the ozone generator is stopped during the refresh period of the semiconductor ozone sensor, when the predetermined time has passed since the end of the refresh period, It is preferred that the ozone generator is activated.

Furthermore, in the ozone concentration control system of the present invention, the ozone generator includes an ultraviolet lamp that emits ultraviolet light, and a power source that supplies power to the ultraviolet lamp.
It is preferable that the control device controls the amount of ozone generated in the processing space by controlling the amount of power supplied from the power source to the ultraviolet lamp.

A zero-point correction method for a semiconductor ozone sensor according to the present invention includes a gas sensitive part and a heater for heating the gas sensitive part, and a measurement period in which the heater is in an operating state and the heater is in a resting state. A zero-point correction method for a semiconductor ozone sensor driven so that the refresh period is periodically repeated,
The output value obtained by the semiconductor sensor is set as a new zero output value at the start of the measurement period after the end of the refresh period of the semiconductor ozone sensor.

  In the ozone concentration meter used in the ozone concentration control system of the present invention, the semiconductor ozone sensor is driven intermittently, so that the adsorbed gas to the semiconductor ozone sensor is reduced during the refresh period of the semiconductor ozone sensor. It is assumed that it has been removed to some extent. The sensor output value including the drift amount with respect to the set zero point obtained at the start of the measurement period after the end of the refresh period is assumed to be the zero point. Can be measured. Therefore, according to the ozone concentration control system of the present invention, the ozone concentration in the processing space can be accurately controlled using the gas concentration meter equipped with the semiconductor type ozone sensor.

  Further, in the zero correction method of the semiconductor ozone sensor of the present invention, the drift amount with respect to the set zero point obtained by the semiconductor ozone sensor at the start of the measurement period after the refresh period of the semiconductor ozone sensor is completed. The sensor output value including is assumed to be zero. Therefore, according to the zero correction method of the semiconductor ozone sensor of the present invention, it is possible to compensate for fluctuations in the sensor output caused by exposure to the ozone atmosphere for a certain time or more, so that the detection accuracy of ozone concentration is improved. Can do.

It is a figure which shows roughly an example of a structure of the ozone concentration control system of this invention. It is a timing chart which shows the operation | movement sequence in the ozone concentration control system shown in FIG. It is a figure which shows the output characteristic by the ozone concentration meter using the ultraviolet absorption method (absorbance method), and the output characteristic by the ozone concentration meter provided with the semiconductor type sensor.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a diagram schematically showing an example of the configuration of the ozone concentration control system of the present invention.
This ozone concentration control system includes an ozone concentration meter 10 that measures the ozone concentration in the processing space S, an ozone generator 20 that releases ozone in the processing space S, and a target ozone concentration that is set in the processing space S. And a control device 30 that controls to be maintained. The processing space S has an atmosphere in which oxygen exists, for example.

As the ozone concentration meter 10, a device provided with a semiconductor type ozone sensor having a gas sensitive part made of a metal oxide semiconductor material and a heater for heating the gas sensitive part is used. In this semiconductor type ozone sensor, gas is generated by ozone coming into contact with the surface of the gas sensitive part in a state where the gas sensitive part is heated by supplying a current controlled to a constant magnitude to the heater. The amount of change in the resistance value of the unit is detected, and a voltage signal corresponding to the ozone concentration is output.
In the ozone concentration control system of the present invention, the semiconductor ozone sensor is driven intermittently so that the ozone concentration measurement period in which the heater is in the operating state and the refresh period in which the heater is in the inactive state are periodically repeated. Is done. Here, in the ozone concentration measurement period, the surface temperature of the gas sensitive part in the semiconductor ozone sensor is heated to a state of 350 to 450 ° C., for example. In the refresh period, the temperature of the gas sensitive part is lowered to a low temperature state, for example, room temperature, thereby reducing the surface of the gas sensitive part.

  As the ozone generation device 20, for example, a configuration that industrially generates ozone using a photochemical reaction method using ultraviolet light, or a configuration that industrially generates ozone using a silent discharge method. However, it is preferable to use a photochemical reaction method. This is because, in the photochemical reaction method, even when a gas containing nitrogen and oxygen is used as the source gas, nitrogen oxides are not generated as in the silent discharge method, for example.

The ozone generator 20 in this example uses a photochemical reaction method, and is configured by an ultraviolet irradiation device 21 that includes an ultraviolet lamp 22 that emits ultraviolet rays and a power source 23 that supplies power to the ultraviolet lamp 22. ing.
As the ultraviolet lamp 22, for example, a low-pressure mercury lamp or an excimer lamp can be used, but an excimer lamp capable of emitting light that does not include the ozone decomposition wavelength is preferably used.

  The control device 30 is based on a sensor driving circuit that intermittently drives the semiconductor ozone sensor in the ozone concentration meter 10, a lamp lighting circuit that controls the lighting of the ultraviolet lamp 22, and an output (voltage signal) from the semiconductor ozone sensor. An ozone concentration calculating means for calculating the ozone concentration, and a storage means in which data relating to the calculation of the ozone concentration and data relating to a zero point correction process described later are recorded.

During the ozone concentration measurement period, the sensor driving circuit supplies a constant current of a predetermined magnitude to the heater so that the heater is in an operating state, and during the refresh period, power supply to the heater is stopped and the heater is in a resting state.
The ozone concentration measurement period is 1 to 10 minutes, for example, 5 minutes, and the refresh period is 1 to 5 minutes, for example, 1 minute.

  The lamp lighting circuit has a function of controlling the amount of power supplied to the ultraviolet lamp 22. Since the intensity of ultraviolet rays emitted from the ultraviolet lamp 22 depends on the value of electrical energy input to the ultraviolet lamp 22, the amount of ozone generated in the processing space S is controlled by controlling the amount of power supplied to the ultraviolet lamp 22. can do.

  In the storage means, the sensor output value of the semiconductor ozone sensor corresponding to the target ozone concentration in the processing space S is set (recorded) as the reference output value (A). This reference output value (A) is, for example, a sensor output value of a semiconductor ozone sensor that has been calibrated. The storage means records output characteristic data (calibration curve data) indicating the relationship between the sensor output of the semiconductor ozone sensor and the ozone concentration.

Hereinafter, the operation of the ozone concentration control system will be described.
FIG. 2 is a timing chart showing an operation sequence in the ozone concentration control system shown in FIG. (A) is a figure which shows the relationship between the sensor output voltage value from a semiconductor type ozone sensor, and a reference sensor output voltage value, (b) is a chart which shows the lighting state of an ultraviolet lamp, (c) is an ultraviolet absorption method. The figure which shows the ozone density | concentration in the processing space measured with the ozone concentration meter using (absorbance method), (d) is a figure which shows the ozone concentration value shown on the display part of an ozone concentration meter.

  In the above ozone concentration control system, when the ozone concentration measurement in the processing space S by the ozone concentration meter 10 is performed, the gas sensitive part in the semiconductor ozone sensor is heated, and the miscellaneous gas adsorbed on the surface of the gas sensitive part A warm-up process (sensor activation) for removing moisture is performed. The time during which the warm-up process is performed is set according to the non-energization time of the semiconductor ozone sensor. The heating conditions in the warm-up process may be the same as or different from the heating conditions in the ozone measurement period.

Then, when the warm-up process is performed and the semiconductor ozone sensor is activated so that the ozone concentration can be measured (time T1 in FIG. 2A), the ultraviolet lamp 22 in the ozone generator 20 is turned on. At the same time, the semiconductor ozone sensor is intermittently driven to measure the ozone concentration in the processing space S. When the ultraviolet lamp 22 is turned on, ozone is generated by irradiating the ultraviolet rays from the ultraviolet lamp 22 to the oxygen in the processing space S. Therefore, as shown in FIG. The ozone concentration inside increases gradually. Further, as is clear from FIGS. 2A and 2C, the sensor output voltage value by the semiconductor ozone sensor and the ozone concentration value measured by the ozone concentration meter using the ultraviolet absorption method (absorbance method) are also shown. It is understood that there is a gradual increase. The sensor output voltage value of the semiconductor ozone sensor is displayed on a display unit in an ozone concentration meter (not shown). The display unit substantially corresponds to the ozone concentration display unit.
The control device 30 compares the reference sensor output voltage value corresponding to the target ozone concentration value stored in advance with the sensor output voltage value (actually measured value) output from the semiconductor ozone sensor, and outputs the sensor output voltage value. Is lower than the reference sensor output voltage value, the ultraviolet lamp 22 in the ozone generator 20 is continuously turned on, and when the sensor output voltage value is greater than or equal to the reference sensor output voltage value, ozone generation is performed. The ultraviolet lamp 22 in the apparatus 20 is turned off.

  In the ozone concentration measurement period M1 of the semiconductor ozone sensor, the sensor output voltage value by the semiconductor ozone sensor corresponds to a preset target ozone concentration at a time T2 when a predetermined time has elapsed since the ozone generator 20 was activated. When the control device 30 detects that the reference sensor output voltage value A has been reached, it is determined that the ozone concentration in the processing space S has reached the target ozone concentration, and as shown in FIG. The lamp 22 is turned off. When the ultraviolet lamp 22 is turned off, the lifetime of the generated ozone is about several tens of seconds, so that the ozone concentration in the processing space S gradually decreases with time. As shown in FIG. 2 (c), it is shown that the ozone concentration value measured with an ozone densitometer using the ultraviolet absorption method (absorbance method) gradually decreases. The sensor output voltage value by the semiconductor ozone sensor should also gradually decrease as in the output characteristic shown in FIG. However, as shown in FIG. 2 (a), the sensor output voltage of the semiconductor type ozone sensor has drifted due to the semiconductor type ozone sensor being exposed to ozone for a certain period of time, and the sensor output voltage value is The result is that the drift amount is added and the decrease in ozone concentration is moderate.

  Then, when the semiconductor ozone sensor shifts from the ozone concentration measurement period M1 to the refresh period R1 and is in a rest state (time point T3), the semiconductor ozone sensor starts to be refreshed. That is, the gas sensitive part is cooled to a low temperature state for a predetermined time by stopping the heating of the gas sensitive part by the heater. Thereby, the gas adsorbed on the surface of the gas sensitive part is reduced and the drift is eliminated to some extent. In the refresh period R1, the resistance value of the gas sensitive part increases due to the low temperature physical properties of the metal oxide film semiconductor, so that the sensor output voltage indicates the MAX voltage state.

  At the start time T4 of the ozone concentration measurement period M2 after the end of the refresh period R1 of the semiconductor ozone sensor, if the refresh of the semiconductor ozone sensor has been completely performed, the gas adsorbed on the surface of the gas sensitive part is Since it is in the removed state, even if ozone is present in the processing space S, the sensor output voltage value should be zero at the instant T4 of the ozone concentration measurement period M2. However, during the refresh period R1 (for example, 1 minute), the influence of drift cannot be completely eliminated, so the sensor output voltage value does not become zero.

Thus, in the above ozone concentration control system, the zero correction process of the semiconductor ozone sensor is performed by the control device 30 at the start time T4 of the ozone concentration measurement period M2 after the refresh period R1 of the semiconductor sensor ends. .
In the zero point correction process, first, the sensor output voltage value of the semiconductor type ozone sensor acquired at the start time T4 of the ozone concentration measurement period M2 is stored as the fluctuation amount Ad1 with respect to the zero output value set for the semiconductor type sensor. To record. That is, the sensor output voltage value of the semiconductor ozone sensor acquired at the start time T4 of the ozone concentration measurement period is assumed as a new zero output value. Then, the sum of the preset reference sensor output voltage value A and the fluctuation amount Ad1 is updated and set as a new reference sensor output voltage value (A + Ad1).
Further, after such a zero point correction process is performed, the ozone concentration value in consideration of the fluctuation amount Ad1 of the sensor output is displayed on the display unit of the ozone concentration meter 10.

When the ozone concentration measurement is started, the semiconductor-type ozone sensor is heated to a predetermined temperature until the sensor output is stabilized (hereinafter referred to as “delay time”) Δd. The sensor output voltage value of the ozone sensor increases rapidly to the sensor output voltage value corresponding to the actual ozone concentration in the processing space S.
On the other hand, the ozone concentration in the processing space S is lower than the target ozone concentration because the ultraviolet lamp 22 in the ozone generator 20 is turned off. Therefore, in the ozone concentration measurement period M2 after the end of the refresh period R1, the ultraviolet lamp 22 is turned on by the control device 30 and the ozone generation device 20 is operated. The ultraviolet lamp 22 may be turned on at the start time T4 of the ozone concentration measurement period M2, but is turned on at a time T5 when a predetermined time (delay time Δd) has elapsed from the start time T4 of the ozone concentration measurement period M2. Is preferred. This is because the sensor output of the semiconductor ozone sensor is more stable (or in a stable state) after the delay time Δd has elapsed, and the measurement result of the ozone concentration in the processing space S has high reliability. It is because it is obtained. Note that the length of the delay time Δd may be set to a predetermined length by, for example, experiments.
In the vicinity of the delay time Δd, there is a portion where the heating of the semiconductor ozone sensor is completed and the output voltage waveform becomes flat. The ultraviolet lamp 22 may be turned on at the start of the flat portion. The start point of the flat portion may be a point in time when the rate of increase (dVm / dt) in the sensor output voltage value is near 0 or-(minus).

In the ozone concentration measurement period M2 of the semiconductor ozone sensor, a new reference voltage value in which the sensor output voltage value by the semiconductor ozone sensor is updated and set at a time T6 when a predetermined time has elapsed since the operation of the ozone generation device 20 is performed. When it is detected by the control device 30 that it has reached (A + Ad1), it is determined that the ozone concentration in the processing space S has reached the target ozone concentration, and the ultraviolet lamp 22 is turned off as shown in FIG. Is done.
Thereafter, the semiconductor ozone sensor is refreshed, and procedures such as the zero point correction process (detection of drift amount, update setting of reference sensor output voltage value) as described above are repeated. In FIG. 2A, T7 is the time when the ozone concentration measurement period M2 ends, T8 is the time when the refresh period R2 ends, and T9 is the time when the operation of the ozone generator 20 is started (the ultraviolet lamp 22 is turned on). When it is lit). T10 is the time when the sensor output voltage value of the semiconductor ozone sensor reaches a new reference sensor output voltage value (A + Ad2) that has been updated, Ad2 is the ozone concentration measurement period after the end of the refresh period R2 of the semiconductor ozone sensor This is a fluctuation amount (drift amount) of the output value obtained by the semiconductor ozone sensor at the start time T8 of M3 with respect to the zero output value set for the semiconductor sensor.

  Thus, in the ozone concentration meter 10 used in the ozone concentration control system, the semiconductor ozone sensor is intermittently driven, so that the refresh period (R1, R2,...) Of the semiconductor ozone sensor. In FIG. 4, the adsorbed gas for the semiconductor ozone sensor is removed to some extent. The sensor output including the drift amount with respect to the set zero point (zero output value) obtained at the start of the ozone concentration measurement period (M2, M3,...) After the end of the refresh period (R1, R2,...). Since the zero point correction process in which the voltage value is assumed to be a zero point is performed, it is possible to compensate for variations in sensor output caused by exposure to an ozone atmosphere for a certain period of time. For this reason, the detection accuracy of the ozone concentration can be improved, and the ozone concentration in the processing space S can be measured with a certain accuracy. Therefore, according to the ozone concentration control system of the present invention, the ozone concentration in the processing space S can be accurately controlled using the gas concentration meter 10 provided with a semiconductor sensor.

  Hereinafter, experimental examples performed for confirming the effects of the present invention will be described.

<Experimental example 1>
Using an ozone concentration meter equipped with a semiconductor type ozone sensor, the semiconductor type ozone sensor is intermittently driven so that the ozone concentration measurement period and the refresh period are periodically repeated, and the ozone concentration measurement period after the end of the refresh period While performing the zero point correction process that simulates the sensor output voltage value acquired at the start point as the zero point, the ozone concentration in the processing space in a state where the ozone concentration is maintained at 0.5 ppm was measured. The ozone concentration measurement period was 5 minutes and the refresh period was 1 minute.
As a result, it was confirmed that the ozone concentration can be measured within an error range of ± 10%, and the ozone concentration can be measured with the same accuracy as an ozone concentration meter using an ultraviolet absorption method (absorbance method). .

DESCRIPTION OF SYMBOLS 10 Ozone concentration meter 20 Ozone generator 21 Ultraviolet irradiation apparatus 22 Ultraviolet lamp 23 Power supply 30 Control apparatus

Claims (4)

An ozone concentration meter for measuring the ozone concentration in the processing space, comprising a semiconductor ozone sensor;
An ozone generator for releasing ozone into the processing space;
The semiconductor ozone sensor is driven so that an ozone concentration measurement period in which the heater in the semiconductor ozone sensor is in an operating state and a refresh period in which the heater is in a resting state are periodically repeated, and the semiconductor ozone sensor A control device for controlling the ozone generator so that the processing space is maintained at a set target ozone concentration based on an ozone concentration measured by a sensor;
In the control device, an output value for the semiconductor ozone sensor according to the target ozone concentration is set as a reference output value (A),
The variation (Ad) of the output value obtained by the semiconductor ozone sensor at the start of the ozone concentration measurement period after the refresh period of the semiconductor ozone sensor with respect to the zero output value set for the semiconductor ozone sensor The ozone concentration control system is characterized in that zero point correction processing is performed to update and set the sum of the reference output value (A) as a new reference output value (A + Ad).   When the operation of the ozone generator is stopped during the refresh period of the semiconductor ozone sensor, the ozone generator is activated when a predetermined time elapses from the end of the refresh period. The ozone concentration control system according to claim 1. The ozone generator includes an ultraviolet lamp that emits ultraviolet rays, and a power source that supplies power to the ultraviolet lamp.
3. The ozone concentration control according to claim 1, wherein the control device controls an ozone generation amount in a processing space by controlling an amount of power supplied from the power source to the ultraviolet lamp. system. It comprises a gas sensitive part and a heater for heating the gas sensitive part, and is driven so that a measurement period in which the heater is in an operating state and a refresh period in which the heater is in a dormant state are periodically repeated. A zero-point correction method for a semiconductor ozone sensor,
A zero correction method for a semiconductor ozone sensor, characterized in that an output value obtained by the semiconductor sensor is set as a new zero output value at the start of a measurement period after the refresh period of the semiconductor ozone sensor ends.

Images