DE3023625A1 - SYSTEM FOR MONITORING THE CONCENTRATION OF A SPECIFIC GAS IN A (ENVIRONMENTAL) SAMPLE - Google Patents

Description

DIPL. ING. HEINZ BARD £ HLE PATENT ADVOCATE

File number:

Applicant: Thermo Electron Corporation 101 First Avenue Waltham, Mass. 02154 United States

/ C 7 L · S ν / γ- Munich, June 24, 1980

My reference: ρ 3Q86

"System for monitoring the concentration of a specific gas in an (ITmWeIt) sample" ^:

030063/0838

description

The invention relates generally to absorption cell gas monitors and, more particularly, to the compensation of errors, resulting from successive measurements from absorption cell gas monitors, and their setting up Zero with no loss of data discovery time.

The presence or concentration of a gas or vapor in a sample is often determined by the characteristic Absorption or attenuation of radiation of certain wavelengths. For a given gas or steam, that (which) is to be measured or monitored, the sample is irradiated by energy of a wavelength which is through the gas or steam to be monitored is absorbed in a significant manner. Another factor which affects the choice of wavelength is, of course, the inability of other gases to be believed that they are also present in the sample, the radiation of the selected wavelength is more significant Way to absorb.

The range used in absorption engineering Wavelength is pretty broad; Gases such as ozone or sulfur dioxide, and vapors such as acetone and benzene, significantly absorb radiation with wavelengths falling in the ultraviolet range. on the other hand wavelengths in the infrared range are easily caused by gases such as NO ", CO" and H "S, as well as by water vapor absorbed.

030063/0838

While the present invention is primarily concerned with ozone measurements, it is also applicable to Measurement of other gases and vapors, if appropriate changes in the radiation source and in the rest Components are made.

In a basic arrangement for monitoring the presence or concentration of a specific gas or vapor are the transmission of radiation of a suitable wavelength through a sample cell, which is first a sample from which the specific gas has been removed, and the transmission of the same energy through it Cell, if it contains the same sample from which the specific gas has not been removed, with each other compared.

The theoretical basis for these measurements is formed

(-klc)

~ ^e

the Beer-Lambert law: ^ / ^ - r,

in which for the specific case of ozone monitoring

mean:

I - photocurrent, measured in the radiation that has passed an ozone-containing (environmental) sample, I »= photocurrent, measured in the radiation that passes the sample from which ozone has been removed

Has,

k - absorption coefficient (at 254 nm for ozone),

c = ozone concentration,

1 = length of the absorption chamber and e = base of the natural logarithm.

030083/0838

Generally, in known systems, radiation from a suitable light source becomes a sample cell or chamber which first contains an (environmental) sample from which ozone has been removed, and it will I measured. Then the first sample in the cell is replaced with a sample from which ozone has not been removed, the radiation is allowed to pass through the cell again and I is measured. The difference between the transmissions measured by means of suitable photoelectric devices provide a measure of the ozone concentration in the sample.

It is also common to place a reference detector in a position directly opposite the light source and the Output values (output) of the reference detector can be used to compensate for fluctuations in the power output of the Light source can be used.

Measurements made in the manner described above have found some useful ones Results, but the accuracy of these results is insufficient for several reasons. For example a sample can be passed through a suitable chamber using a scrubber or other ozone removal device contains. Although the ozone removal chamber serves its purpose, the concentration of other gaseous and vaporous components, which also absorb radiation at 254 nm, as a function fluctuate from time. This creates errors when successive measurements are taken.

030083/0838

In some procedures, a single absorption cell is created used and in addition to the time delay between the measurement of the transmission through the sample from which Ozone has been removed and the measurement of transmission through the ozone-containing sample is data collection time lost because the system with the sample must be flushed without ozone before taking measurements to create a "zero base". As a rule, in the process of flushing, creating the zero base and It takes up to half a minute to carry out a single measurement. At a given time of half a minute, less than 10% of the available time can be used for the actual measurement will.

An object of the present invention is to avoid the presence of gases or vapors with the like Radiation absorption properties such as the gas to be monitored or the steam to be monitored resulting errors to be eliminated or kept to a minimum. Another aim of the invention is to avoid the errors from the delay between the measurement of the absorption by the gas to be monitored or the to monitored vapor containing sample and through the sample from which the gas to be monitored or the gas to be monitored Steam has been removed result. Another object of the invention is, in the system in where gas monitoring is performed to maintain an accurate zero setting at a minimum

030063/0838

Loss of data collection time.

In practicing the invention, the basic absorbent cell concepts set forth above are followed. However, a reference absorption cell is placed between the radiation source and the reference detector. A sample from which the gas to be monitored, such as ozone, has been removed is continuously passed through the reference absorption cell is passed through and the absorption is continuously recorded by means of the reference detector. An essentially continuous flow of the (environmental) sample allows the effect to be extinguished (eliminated) of gases or vapors other than ozone that absorb light at 254 nm in real time. It also measures the reference detector the set of fluctuations in the Lamp intensity and the measured photocurrent in the radiation through the reference cell is simultaneously with the measured photocurrent in the radiation passing through a sample cell containing ozone. aside from that the structure of the device, which has the function of removing ozone from the sample, optimized so that the flushing time is minimal. This is achieved by reducing their volume as much as possible and if necessary an accumulator (memory) of a comparable size and shape is provided through which the (environmental) sample is passed simultaneously with its passage through the ozone removal device.

In order to obtain updated measurements more frequently (measurements that are up to date), the system

030063/0838

a second sample absorption cell can be provided. The additional cell is timed so that it with a 50% duty cycle in a phase shift of 180 against the basic sample cell works. While one cell is providing data, the other cell can be purged and set to zero.

The invention relates in particular to an absorption cell system for the measurement and monitoring of the concentration of specific gases in an (environmental) sample, the comprises at least one sample absorption cell into which an (environment) containing the specific gas to be monitored Sample is introduced, and a reference absorption cell in which the (environmental) sample from which the specific Gas has been removed, a source of radiation of a wavelength different from that introduced by The specific gas passed through the cell is absorbed, with the intensities of the cells passing through Radiation measured (detected) separately and then compared with one another and calculated in a microcomputer which provides output data relating to the concentration of the specific gas in the (near) sample.

In the system according to the invention, the reference absorption cell is arranged in the path of the radiation from the radiation source, so that fluctuations in the intensity of this radiation can be monitored while simultaneously in absorption occurs in the sample cell. To avoid errors resulting from changes in the concentrations of gases other than the specific gas to be monitored

030083/0838

Depending on the time, the structure of the device in which the specific gas is removed, optimized to the measurements of the (environmental) sample and the (environmental) sample without the specific gas synchronize.

A second sample absorption cell is used to increase the measurement frequency built into the system and with a phase shift of 180 compared to the first sample absorption cell operated, which is required for zeroing in a sample cell while in the other measurements can be performed.

Further objects, features and advantages of the invention will become apparent from the following detailed description in conjunction with the accompanying drawings, which are useful for a better understanding of the present invention. Show:

Figure 1 is a schematic diagram of an embodiment an ozone monitor;

Figure 2 is a schematic diagram of a second embodiment of an ozone monitor; and

Figure 3 is a block diagram of the electronic part of the instrument.

In Fig. 1 of the accompanying drawings, an opening 12 is shown for the introduction of an (environmental) sample which is in direct communication with a chamber 14 which contains an ozone removal catalyst. The ozone removal catalyst can be in the form of a fixed bed filter made of metal

030063/0838

oxides are present, but other ozone removal systems can also be used be used. The insertion opening 12 can use an accumulator (memory) (not shown) of the same general size and shape as the Chamber 14 may be connected or it may be in direct communication with an inlet of a 3-way solenoid valve 16. The chamber 14 is in communication with a second inlet of the valve 16. Chamber 14 is up also in connection with a reference cell 20 via a line 18. From the outlet of the valve 16 runs another line 22 to a sample cell 24. An outlet line 26 extending from the reference cell 20 is included a similar line 28 which extends from the sample cell 24 is connected. A line 30 connects the combined Outlets with a flow meter 32, the outlet of which is connected to a pump 36 via a needle valve 34. The pump 36 continuously withdraws the contents of the system through an outlet 38. The various solid ones Lines and the elements described represent a simplified representation of the mechanism as he occurs when gas flows through the monitor equipment.

In addition to the solid lines, which indicate the gas flow through the apparatus, dashed lines show the path of the radiation, in the case of ozone monitoring in the form of light. The light is generally preferably generated by means of a low-pressure mercury-vapor lamp 40, the output of which is a line containing about 95 7o of the total energy at 254 nm and pointing to a

030083/0838

Most mirror 42 and a second mirror 44 is aligned. From the mirror 42 the light is drawn through the length of the reference cell 20 is directed to a reference detector 46. The reference detector 46 may be any of several known devices, such as a solar blind vacuum photodiode detector sensitive to radiation of a wavelength of 254 nm be. The output current of the detector 46 is determined by the intensity of the radiation the pre-selected wavelength impinging on the detector. This way it becomes an effective monochromator formed for the determination of ozone. At the same time, light is emitted from the light source 40 by means of the mirror 44 reflected through the length of the sample cell 24 onto a sample detector 48, which in all respects is the reference detector 46 may resemble.

Next to the solid lines, which show the gas flow, and the dashed lines, which show the light paths show, dash-dotted lines show the path of the electrical signals. A signal comes in the form of a stream from the reference detector 46 and is applied to a reference digital electrometer and a voltage-to-frequency converter 50 abandoned. The output of element 50 becomes abandoned to a microcomputer unit 52 which has a standard 8-bit microprocessor and other elements such as they are described below. At the same time, a comparison signal is generated in the sample detector 48 and applied to a sample digital electrometer and voltage to frequency converter 54. The output of the Element 54 is also placed on unit 52.

03 0063/0838

In addition to the supply of data for the display or for another use at a data output 60, the microprocessor is also used of the element 52 programmed so that it has a suitable output (output) for the control (control) of the Operation of the solenoid valve 16 results.

The electrical mode of operation of the instrument according to FIG. 3 is shown in greater detail in FIG. That from the Signal derived from reference detector 46 is first converted into a voltage in an electrometer 82 and then by voltage-frequency Converter 92 converted to a frequency. The output of the converter 92 is from a counter 72 for a specific period of time determined by the microprocessor 90 is counted.

At the same time, the comparison signal from the sample detector 48 is passed through the electrometer 84, the voltage-frequency converter 94 and the counter 74 treated in a similar manner.

The microprocessor 90 is in a read-only memory 85 programmed and during its operating time through a peripheral interface adapter 95 with the solenoid valve 16 connected. The microprocessor 90 is also programmed to receive data from the counters 72 and 74 in the Random memory 87 stores. The microprocessor calculates also the ozone concentration, which is used as output analog data in a data output 91 and as a digital output in a display device 97 or in a data output 98 is issued.

030063/0838

-VF-

3023825

During operation, the gas to be monitored enters the inlet opening 12 on and the 3-way valve 16 is set by the timer program of the microprocessor 90 so that that the gas flows through the ozone removal chamber 14 through the cell 24 and finally through the outlet 38 is withdrawn by continuously operating the pump 36. The control (regulation) of the current can be done by means of needle valve 34 in accordance with readings obtained from flow meter 32 will. After the system has been completely flushed using the sample without ozone, the system can access the can be set to zero in the manner described below. The values come from the reference detector 46, the one Results in current which varies according to the absorption of radiation in the reference cell 20, and synchronously they come from the sample detector 48, which produces a current corresponding to the absorption of the radiation in of the sample cell 24 into which the (environmental) sample has been introduced in the manner described below is. These currents are converted into a voltage by the reference electrometer 82 and the sample electrometer 84, respectively and the voltages are given by the reference voltage-to-frequency converter 92 and the sample voltage-frequency converter 94 converted into frequencies. The frequencies are then counted synchronously by the reference counter 72 and the sample counter 74 for a period of time that may be about one second as controlled by microprocessor 90. These values are in a random memory (RAM) 87 of the microcomputer system for

030083/0838

saved for later use.

An (environmental) sample is either taken directly through the inlet port 12 or by an accumulator (memory) (not shown) of generally the same size and the same shape as the chamber 14 is introduced. Even if the chamber 14 is kept at very small dimensions there is a finite delay time and to ensure that both the (environmental) sample and the (environmental) sample without ozone originate from the same sample, the accumulator (memory) can be used to delay the flow of the (environmental) sample just as the Chamber 14 delays the flow of the (environmental) sample without ozone, regardless of whether an accumulator (memory) is used or not, a signal from the microprocessor 90 and peripheral interface adapter 95 switches the valve 16 after the zero setting, so that the (environmental) sample from the inlet opening 12 through the valve 16 and the line 22 can flow to the sample cell 24. Again after a suitable delay which is the full Loading of the sample cell with the (environmental) sample is allowed, the current through the sample detector 48 measured as a function of the absorption of the radiation from the lamp 40 in the sample cell 24.

The current from the reference detector 46 also becomes synchronous as a function of the absorption of the radiation from the lamp 40 measured in the reference cell 20. The output values of the sample detector 48 and the reference detector 46 become then to digital form as described above

030063/0838

-10-

converted and together with the previously saved values stored in the random memory 87.

During the cycle the temperature and pressure are measured by suitable transducers 75 and 77, respectively. The voltage off Output values of these converters are converted into a frequency by the voltage-frequency converters 96 and 98, respectively and counted by counters 76 and 78, respectively, under a timing control (timing) of the microprocessor 90. These Values are also stored in RAM 87.

The practical calculation according to Beer-Lambert's law is carried out as follows: The ratio I / I _n »also known as the transmittance T, where I is the intensity that would have been determined by the sample detector 48 at the same instant that I can be calculated from the stored intensity measured at zero setting by sample detector 48 divided by the intensity determined by reference detector 46 at zero setting multiplied by the intensity determined by reference detector 46 during sampling .

In a typical ozone monitoring system where k at 254 nm 308 atm "cm at standard temperature and pressure (273 ° K and 1 atm) and 1 is the length of the cell, e.g. B. 78.8 cm., The ozone concentration can be calculated from the following equations:

-log _e (1 / I ₀ ) = klc (1) c = -l / kl log _e (1 / I ₀ ) (2)

030063/0838

To determine c in parts per million (parts per million), equation (2) is multiplied by 10. The concentration at other pressures and temperatures than STP (standard values) stand according to the ideal gas law with the concentration at STP in relationship. Thus equation (2) becomes:

c (ppm) = -10 ⁶ / kl χ (76O) / P χ T / 273 log _e (1 / ^ (3)

where P is in mm and T is in degrees K. The equation (3) is also automatically processed by the microcomputer solved.

The temperature transducer 75 and the pressure transducer 77 are switched into the microcomputer (interfaced) in order to accept changes to correct these variables continuously. The pressure transducer is preferably at the outlet of the sample cell arranged and the temperature converter can be arranged in the middle of this cell.

In Fig. 2, much of the circuit and apparatus is similar to that of Fig. 1. The same insertion port is used 12 and ozone removal chamber 14 as well as the same flow meter 32, needle valve 34 and the Pump 36 and the outlet port 38 are used. A mercury lamp 40 with mirrors 42 and 44 is also used, the mirror 42 reflecting light through the reference cell to a reference detector 46, the output of which a digital electrometer 50 and a converter for storage in a microcomputer 52 passes.

030063/0838

Similarly, mirror 44 reflects light through sample cell 42 to detector 48, the output of which is integrated and converted into a frequency in the element 54 and also sent to the microcomputer 52 will.

In addition to a sample cell 24, however, a second sample cell 24a is used. The radiation from the mercury lamp 40 impinges directly on the sample cell 24a instead of being deflected by mirrors. A sample detector 48a works in conjunction with the sample cell 24a and the output of the sample detector 48a occurs the electrometer and the converter 54a and enter the microcomputer 52.

Because of the additional sample cell, sample detector and electrometer converter, there are some additional components necessary. Although the sample entering the inlet opening 12 and passing through the chamber 14 is closed reaches the 3-way valve 16a, the chamber 14 is, for example, different from the device according to FIG. 1 not only via the line 18 with the reference cell 20 in connection, but it is also through the line 19 with connected to the inlet of the second 3-way solenoid valve 16. In addition, the inlet port 12 is not only in communication with the valve 16, but it is also connected to an inlet of the valve 16a. An outlet line leads from valve 16 to the sample cell 24 as in the device of FIG. 1 and a second line leads from an outlet of the valve 16a to the

030083/0838

Sample cell 24a.

The electrical connections for operating the valves 16 and 16a are also somewhat more complicated as there are connections from the microcomputer 52 to both valves 16 and 16a. The microprocessor of element 52 is also programmed somewhat differently in order to achieve more complex timing signals which are required to operate or switch the 3-way valves 16 and 16a. As stated earlier, in order to achieve accuracy in the range of ppb ozone concentrations. (Parts per billion parts) it is desirable that the system be zeroed again as often as possible. In the device according to FIG. 2, a preliminary rinsing is first carried out. Then, a reading of _n is I, which originates from the output of the reference detector 46 is carried out and stored in the microcomputer 52nd

The microprocessor of element 52 is then programmed to that a series of operations is performed. First a signal is given to the valve 16 to be closed trigger (control) and the (environment) sample about 20 seconds to the sample cell 24 for a long time, reading values and collecting data every second. A sample is allowed to flow synchronously without ozone and the sample cell 24a is rinsed for a period of 9 seconds. Then, for two seconds, values of the transmission through the sample without ozone in the sample cell 24a read to enable a new zero setting. The sample is then rinsed again for 9 seconds.

030083/0838

cell 24a carried out. At this point the cell 24a is ready for the introduction of an (environmental) sample. If the (Environment) sample is then introduced into the sample cell 24a, the valves are triggered by the microprocessor 90 (controlled) so that the sample can be introduced into a rinse sample cell 24 without ozone. The new zero setting the sample cell 24 then takes place, while in the sample cell 24a the ozone concentration in the (environmental) sample is monitored.

By switching (adjusting) in the manner described, the two sample cells operate with a phase shift of essentially 180. While one cell is being purged and zeroed, each cell in the other Second monitoring measurements carried out. In this way there is no measurement failure, what for certain Applications, such as in on-board instruments, can be of great importance.

A change in ozone concentration of 0.001 ppm corresponds to a change in transmittance from 1 part to 50,000 Share. In order to determine (prove) the ozone concentration with an accuracy of -f 0.001 ppm, the Do not change the value of I by more than 1 part in 100,000 parts. The lamp energy output intensity is at any conventional way difficult to control and the placement of the reference detector in the path of energy delivery of the lamp leads to a monitoring of the energy output intensity of the lamp by the reference detector at the same time with the output of the in operation

030063/0838

Sample detector. This information is posted to the microcomputer in order to make any changes from I to Correct the time between the time of the actual measurement and the time of use to calculate the concentration may have occurred a few seconds later.

It has been pointed out earlier that ozone is not the only gas or vapor that produces light 254 nm absorbed. If the concentration of these other substances does not vary, their influence on the accuracy falls the measurement essentially gone because they are present when taking measurements of the contents of both the sample cell as well as the reference cell. However, if the concentrations of these other gases are dependent varies with time, it affects the measurement of I. By arranging the reference ze He between the radiation source and the reference detector minimizes this potential error. Any changes to I_ as a result Any fluctuations in the concentration of these other gases are monitored and internally corrected for the same Way like the changes related to lamp energy output intensity.

030083/0838

-24-

R e r s e

ite

Claims (1)

Pat e ntansprüche iJ system for monitoring the concentration of a specific Gas or vapor in an (environmental) sample according to the absorption of radiation of a given Wavelength through this specific gas, characterized in that it comprises: an inlet port (12), into which the (environmental) sample is continuously introduced, the inlet opening (12) with a chamber (14) which contains a material for removing the specific gas, a source 030063 / ΟΘ3 & ORIGINAL INSPECTED le (40) for the radiation of the predetermined wavelength and at least one sample cell (24), which is arranged in the path of the radiation from the source (40), and a combination of a ¹ reference cell (20), which is also in the path of Radiation from the source (40) is arranged, means for connecting «an outlet of the chamber (14) to the reference cell (20) in order to provide a continuous flow of the (environmental) sample without the specific gas through the reference cell (20). valve means (16) for periodically connecting the inlet port (12) to the sample cell (24) to produce an intermittent flow of the (environmental) sample through the sample cell (24), and means for measurement and comparison the absorption of radiation by the contents of the reference cell (20) and the sample cell (24). 2, system according to claim 1, characterized in that the Valve means (16) for periodically connecting the inlet port (12) to the sample cell (24) comprises a 3-way valve (16) with a first inlet connected to the inlet port (12), a second inlet, which is connected to the outlet of the chamber (16), and an outlet which is connected to the sample cell (24) is a timing circuit and means for electrically connecting the timing circuit with the valve (16), so that the (environment) sample and the (ümwelt) sample without the specific gas for given Periods of time can be introduced into the sample cell (24). 030063/0030 3. System according to claim 1 or 2, characterized in that there is a second sample cell (24 a), which is also in is arranged in the path of the radiation, and has a second 3-way valve (16a) which has a first inlet, connected to the inlet port (12) and a second inlet connected to the outlet of the chamber (14) is, and that the second valve (16a) also has an outlet which is connected to a second Sample cell (24a) is connected, and means for electrically connecting the timer circuit to the second valve (16a), whereby the (environmental) sample alternately in the first sample cell (24) and in the second sample cell (24a) can be introduced. 4. System according to one of claims 1 to 3, characterized in that that the specific gas or vapor is ozone and that the material in the chamber (14) Metal oxides include for the removal of ozone from the flowing (environmental) sample, and that they are one with the reference cell (20) and the sample cell (24) connected, continuously operating pump (36) which generates a periodic current of the (environmental) sample therethrough, the timer circuit Signals for the valve (16) are supplied to control (control) the flow time of the ozone-containing (environment) sample from the inlet opening (12) and to control (control) the flow time of the (environmental) sample without ozone from the chamber (14) into the sample cell (24). 5. System according to claim 4, characterized in that 030063/0838 3023621 the timer circuit comprises a microprocessor (90) » which firstly provides signals for the valve (16), whereby the valve (16) closes the ozone removal chamber (14) with the Sample cell (24) connects so that the (environmental) sample can flow through it without ozone in order to rinse it, and the second provides signals for the valve (16) to connect the inlet port (12) to the sample cell (24), so that the (environmental) sample can flow through. 6. System according to one of claims 1 to 5, characterized in that that the timer circuit is a microprocessor (90) which emits signals to the first and the second valve (16, 16a), whereby the (environment) sample and the (environmental) sample without ozone with a phase shift of essentially 180 alternating between the first and in the second sample cell (24, 24a) are introduced. 7. System according to one of claims 1 to 6, characterized in that that there is an accumulator (memory) between the inlet opening (12) and the valve device (16) which resembles the chamber (14) in its volume and in its shape, as a result of which the (environmental) sample can flow into it the system experiences a time delay that is comparable to that of the flow subject to the (environmental) sample without the specific gas. 8. System for monitoring the concentration of ozone in an (environmental) sample according to the absorption of radiation a given wavelength through the ozone, 030063/0838 3023825 characterized by an inlet opening (12) into which the (environmental) sample is continuously introduced, the Inlet opening (12) is connected to the inlet of a chamber (14) which contains material for removing the ozone, a source (4-0) for radiation having a wavelength of substantially 254 nm and a sample cell (24) which located in the path of the radiation from the source (40), a reference cell (20) also in the path of the Radiation from the source (40) is arranged, means for connecting an outlet of the chamber (14) with the reference cell (20) to ensure a continuous flow of the (environmental) sample without ozone through the reference cell (20) through to produce a 3-way valve (16), which in one position of the same, the inlet opening (12) with the Sample cell (24) and, in a second position thereof, connects the chamber (14) to the sample cell (24), a microcomputer (52) which is electrically connected to the 3-way valve (16) for controlling (monitoring) the Position the same according to a pre-determined program to create a periodic stream of the (environment) sample without generating ozone and a periodic flow of the (environmental) sample through the sample cell (24), and by means for measuring the absorption of the radiation by the contents of the reference cell (20) and the Sample cell (24), the last-mentioned device being connected to the microcomputer (52) and this data provides for the calculation therein to obtain output data regarding the concentration of ozone. 9. System according to claim 8, characterized in that D300G3 / 083 & there is also a second 3-way valve (16a), a second Sample cell (24a) also arranged in the path of the radiation, the second valve (16a) so arranged is that in a first position of the same, the inlet opening (12) with the second sample cell (24a) connects and in a second position of the same connects the chamber (14) to the second sample cell (24a), and a device (48a) for measuring the absorption of the radiation in the second sample cell (24a), wherein the microcomputer (52) is also connected to the second 3-way valve (16a) to operate the same control (to control) according to a predetermined program, whereby the first sample cell (24) and the second sample cell (24a) are alternately connected to the chamber (14) for rinsing the same, and to the inlet opening (12) for measuring the absorption of the radiation therein, with the microcomputer (52) also connected to it becomes that it also picks up, stores and calculates the output data from the reference cell detector means (46), the first sample cell detector device (48) and the second sample cell detector device (48a) according to the predetermined program to provide output data substantially continuously, which represent the ozone concentration in the (environmental) sample. 030063/0838