JPS601540A - Testing equipment for presence of specific substance in liquid - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, light emitted from a light source and conducted in a liquid is received by a photodetector, and the photodetector sends a measurement signal whose value increases with the intensity of the light to a processing circuit. The present invention relates to a device for testing the presence of certain substances in liquids, in particular oil in water, by means of a light source.

DE 2715118 A1 discloses that a sample of the liquid to be examined is emulsified to different degrees of darkness by means of an emulsifying device which can be selectively switched to different driving forces, and then the sample is exposed to visible light. A method for testing the oil content of water is disclosed. By means of a processing circuit, the oil content of the water is calculated from the signals taken from the differently emulsified samples. Since water clouded by emulsified oil is particularly attenuated in parallel light, in this known device a collimator is provided between the light source and the measuring point. Therefore, this known apparatus for testing the oil content of water is extremely complex. Furthermore, the known equipment does not permit measurements of low oil content in water, since the light is attenuated only when the water contains a relatively high concentration of emulsified oil.

What is the purpose of Akira Hontsure? The object of the present invention is to obtain a fIJ simple and highly sensitive device for testing the presence of a specific object in a rod, especially the presence of oil in water.

The present invention achieves the above object as follows: the light source emits diffused light having an ultraviolet component, the photodetector has high sensitivity at least to ultraviolet light, and the processing device 1-1 is designed to issue an alarm signal when the measurement number on the first day becomes smaller than the fixed value F9.

Since the oil present in the water at the water temperature reduces the ultraviolet light by absorption instead of by diffusion, a collimator is not needed to focus the light transmitted through the liquid. If the oil content exceeds the fixed value, the oil content of the water is not calculated, but is simply calculated. This simplifies the processing circuitry since only an alarm signal is issued.

It is known from analytical technology to examine liquids with ultraviolet light in order to check their composition. In this case, the test liquid is sequentially exposed to ultraviolet light in a continuous spectral range, and its correct composition can be determined from the spectral state of the resulting test liquid's attenuation. However, this known method can only be used under laboratory conditions.
For economic reasons, it cannot be used to repeatedly test whether the content of a particular substance v7, such as oil in liquid, exceeds a certain limit.

In particular, to test for the presence of oil in water, it is useful for the light source to emit light primarily in the 0.2 to 0.8 μm Wave II range. This allows even low concentrations of oil to be tested. A narrow band with an undulation σ of approximately 0.28 μm has been found to be particularly suitable.

In an advantageous embodiment of the present invention, the photodetector is a phototube generating a train of pulses whose pulse frequency increases with the intensity of the light, the noggles being counted by a noggle counter; This pulse counter is set at the beginning of the measurement interval Wj.
7' to the preset value, and at the end of the measurement period the second
If il' is not reached, the alarm system is activated. By using such a counter, very reliable and accurate measurement results can be obtained.

In another embodiment of the present invention, the total pulse counter is reset to zero at the beginning of each measurement interval and at the beginning of each measurement interval.
At the end of the n11 period, the clock generator that drives the ratio→− father circuit is activated, and said comparator circuit compares the count of said pulse counter with a second preset value, and at the end of the n11 period. If the count of the pulse counter is less than the second preset value, a tri-power signal is sent to the fiIf reporting device. In this case, the processing circuit is clocked by a clock generator, so that the processing circuit operates automatically.

In yet another embodiment of the invention, the comparator circuit compares 11'h of the pulse counter with a second preset value and if J1 is smaller than the second recent value, the first human power G of the AND circuit is determined. This comparison has a comparator that sends a signal, and a clock generator drives the second input of the AND circuit at the end of each measurement period, and the output of the AND circuit marked F'F11'&H. Connected. This AND circuit determines whether the specific oil contamination of the water (16) simply indicates whether the count corresponding to (16) does not yield a predetermined value.
I can do it.

Phototubes do not emit pulses even in the case of radioactive radiation, so
The device of the present invention is also suitable for testing whether there is radioactive material in water by counting and processing the pulses sent from the light heavy 5 tube while the source is turned off. . Therefore, f ``a measurement pause of a certain length is divided into one measurement period tlJ''.
The light source is placed under the FiU street of the clock generator and emits light only during the measurement period, and the first light source is placed at the beginning of the measurement pause.
The pulse counter that was set to the preset value of
Pulses from the photodetector are counted until the end of the measurement pause, and at the end of the measurement pause, the eighth preset (if the measurement is stopped immediately, the alarm device is activated).

In many cases, for example, water can contain slag, but these substances can be detected more easily than oil. An example of such a substance would be a suspended substance "ef" that attenuates not only ultraviolet light but also visible light. It is advantageous for the light source to also emit light at a long wavelength aar ts, and for this photodetector to be coupled to another photodetector that is highly sensitive to this wavelength. A separate processing circuit is provided to send different measurement signals depending on the intensity of the light.
The above measurement signal indicates that if the intensity of the light emitted to the photodetector marked 01 becomes smaller than a predetermined value of 4ti, the processing circuit of the sublayer device should be set to a lower sensitivity setting, or the Prevent layered VC from working. If necessary, for example, when the threshold value is increased by iθ, another processing circuit may display N (attenuation).

Alternatively, light at a different wavelength may be generated by a light source.

In another embodiment νV of the invention, the liquid to be tested is
A metal tube with a quartz window is disposed between the light source and the photodetector. This embodiment can be made inexpensively and is not subject to the influence of surrounding orders.

The full day 11°t- may have an incision that makes the liquid in front of the GA turbulent. These boosters disperse the oil in the water and prevent it from adhering to the quartz window.

Since it is impossible to completely prevent oil and other substances from accumulating on the quartz window after long operations, ultraviolet light or In some cases, visible light may not be present properly, resulting in the alarm device being activated incorrectly. To avoid this, quartz windows must be cleaned regularly. However, this is difficult and complicated when the ia+lI is fixedly mounted in a fixed chamber or vibrine system.

01) In order to simply clean the quartz window, the quartz window is provided in the spherical part of the hemp tube which fits airtightly with a hollow spherical holder, and said holder is placed in a direction approximately tangential G to the metal tube. It is effective to enable rotation around this shaft. ie device without stopping the flow of liquid by turning the spherical part? ``The window can be swept τN without stopping the operation of [.

If it is necessary to test liquids that also significantly attenuate ultraviolet light (e.g. domestic or industrial wastewater), the reduction in the long-wavelength range by the substances mentioned above should be avoided. Reducing the sensitivity to ultraviolet light by adjusting the amount of oil in water is no longer effective because it reduces the sensitivity to senescence. 81. The presence of oil with low ij:;l a in such a liquid is very high, well above the capacity of the liquid, and cannot be determined. An embodiment of
It is immersed in the body and pulled out, and a driving device causes G to be trapped between the light source and the photodetector.

In this case, even if the liquid is not allowed to flow inside the conduit, at least it can come into contact with the liquid freely at the inspection position and is not obstructed by conduits such as pipes. This is the nfJ proposition. Repeated immersion will result in thickening of the material such as oil or floating matter present in the liquid, so that periodic immersion will result in a thickening of the material.

Therefore, by repeated immersion, even low concentration oil can be tested.
j! Significantly attenuates the ultraviolet light of the device. Preferably, said member is a quartz glass shell. Such parts are
It is resistant to most 1p1 edible substances such as acids and alkaline solvents. Member family 111J-like immersion t1
2 and lifting can take place, for example, in a groove when driven by a motor. However, it is also possible to make a particularly simple front sound by means of the following embodiments of the invention, in which the member is wound around a motor-driven cable drum forming the drive device i. Suspended by a wire or cable that is taken and pulled out. This makes it extremely (jti lV3.
Moreover, a reliable device can be obtained.

If the part is in the raised position during the measurement cycle, the jE L field [
In order to ensure that the position of A drive device may also be controlled.

The present invention will be described in detail below with reference to embodiments 11 and 1 of the drawings.

In FIG. 1, a light source 2 that can be controlled 1111 by a light source subunit 1 is disposed in front of a quartz window 3, and controls the liquid flowing in the direction of the arrow 5 within the measurement chamber Φ from 0.2 to 0. ．．
The 8 μm wavelength range, especially about 0.28/lZm wave, is transmitted through diffused light mainly having an ultraviolet component, and is transmitted to a photodetector 7 in the form of a photocathode, which separates quartz windows 8 and 6 by 1jβ. Projected. The constant signal supplied by the photodetector 7 to the pulse counter 9 via the amplification word 8 has a pulse train whose frequency increases in accordance with the intensity of the light projected onto the photodetector 7. 0 each 7u1] At the beginning of the constant W1 interval, the pulse counter 9 is clocked by the clock generator IO for the first time 1υ'i (
f 4't'i & is set to zero. Comparator 11 inputs the 41 number of pulse counter 9 to inputs 12 and 18.
to the value applied by mechanical or electrical means. The comparison signal from this comparator 11 is output to an AND circuit 14.
．． is added to the first human power 11a. Each 1sllll fixed M
At the end of the interval, clock generator 10 applies a second human power pulse 14bc. Both power 14a and 1 of AND circuit 141
When there is a signal at 4b, the AND circuit 1Φ of G-column applies a trigger signal to the 1-information alarm device 15. At this time, this good news device K generates a signal that can be recognized by the operator, and this signal causes the measurement student to flow through the RCT body 111.
Notifies that 1 minute has exceeded the preset value. Light source system 6
1) The unit 1 is controlled by the clock signal 1510 so that the light source 2 emits light only during the measurement period. This black puffer fish “Ei!: it.

is a self-check type, and if it does not appear, use this state p (8 to G ma liquid (I can't test it anymore, so I'm going to use an appropriate \'f 4' to generate a mouth H number. It is preferable to rub it.

The attenuation of the light projected by light source 2 is 1? l 7JI
+

Is attenuated light light? The rC tube 7G is projected onto this light. 9t is a pulse train that supplies a constant signal. It decreases as the attenuation increases JJll. ↑ "(1 constant σ] Clock generation at the start? Intelligence from S t o) l, z /< Noggle counter 9G, number reset to zero at Lus Add 1 digit to comparator 11,
Comparison? Fr 11 passes this signal to another one from the hook saw 12.
Compare with No. d. In the above comparison i□l, the number of pulse counters 9 to be summed is smaller than the preset value added to the input 12, and )lH]i is added to the input 14a of the AND circuit 1t. ff1lJ If the liquid flowing through the constant chamber 4 is not contaminated with other substances, the photocell 7
receives sufficient light and the frequency of the measurement signal applied by the phototube 7 to the pulse counter 9 is so high that the pulse counter 9 reaches the preset value before the end of the measurement period and at the end of the measurement period the AND circuit No number will be sent to the first order. In this case, if the AND circuit 14 receives a signal from the clock generator lO at the end of the measurement period 101, the signal is
4b but does not appear in input 14a, so 1. AND
Circuit 14 does not send a trigger signal to the alarm device.

If the liquid is contaminated with oil and the light is therefore attenuated and #iy& of the pulse counter 9 becomes very slow, the pulse counter 9 will not reach the preset value at the end of the measurement period and the comparator 11 will not reach the preset value until the end of the measurement period. A comparison signal is sent to input 14a. Therefore, at the end of the measurement period the clock generator 10
Also sending a signal to input 14b, the AND circuit 1 generates a trigger signal which is applied to the )1-# device to generate an alarm signal. A D-y lip 70 tube is used instead of the AND circuit, and its D-power receives the output signal of the comparison IK l 1, and its clock power receives the output signal of the comparison IK l 1.
It is also possible to receive a clock signal from 0.

Alternatively, the pulse from the reset event may set the pulse counter 9 to a number corresponding to the signal at input 12, with zero equal to 7-+lj, and the pulse counter may, for example, count down. In this case, the signal representing the final count of the counter may be applied directly (2) to the AND circuit 14, and the comparison IHII may be omitted.

Between the signal applied to the pulse counter 9 at the beginning of the ill period and the signal applied to the AND circuit 11 at the end of the ill period, the clock generator 'a10 sends a signal to the light source control unit 1 to The control unit 1 switches on the light source 2 only during the measurement period.

In order to extend the life 6ri of the light source 2, there may be a longer measurement pause during which the light source 2 does not emit light between measurement periods.

Since the phototube 7 emits a pulse even when it receives radioactive radiation, the device can also be used to determine the presence or absence of radioactive substances in the liquid when the measurement is suspended. These pulses are counted in a pulse counter which is reset to zero by the clock generator 10 at the beginning of the measurement pause.

The digital input device 11 sends a human power 14ac signal only when the pulse counter 9 exceeds the eighth value, which can be preset by the input signal 1B. Grooved. If at the end of the measurement pause the value is greater than or equal to the eighth value, the liquid contains a radioactive substance. Therefore, the measurement 1υ”
At the end of the interval, the clock generator also connects the ANDli'i circuit 141.
When a pulse is sent to the human power 14Ib, the AND circuit 1t sends a trigger for 1 second to the alarm device b:15 and generates a special alarm.

The processing circuit may have a countdown pulse counter 9 set to a first value other than zero at the beginning of each measurement period. In this case, the comparison signal 11 is configured such that the countdown pulse counter 9 sends a signal to the input 14a of the AND circuit 1t unless the countdown pulse counter 9 reaches the second value, for example zero, entered by the input 12.

The embodiment of FIG. 1 furthermore has a further photodetector 27 for visible light, preferably at a good wavelength, as the light source 2 also emits visible light. Otherwise, a separate light source may be provided. The output signal of another photodetector 27, also pulse-shaped for fii +
The signal is sent to another pulse counter 29 via . This pulse counter, like pulse counter 9, is also set to zero by a pulse from the clock generator at the beginning of the surface measurement period.

The counting of the pulse counter 29 is performed by using the input 12 as a gauze.
Instead of a constant signal preset from the outside, a separate comparison signal may be applied to the comparator 11. In this case, the pulse frequencies of the signals from both photodetectors 7 and 27 are usually approximately equal, but could otherwise be roughly matched by shifting the bits of the digital signals.

Therefore, if the visible light is attenuated, for example by floating objects, the threshold for the comparator 11 is reduced, and if this threshold is not reached, the pulse counter 9 sends a signal to the AND circuit at the end of the measurement period.

Another method is to connect the input 12 of the comparator 11 to a constant signal and the output of another counter 29, such as the most significant number output or the carry output, to another input 14C of the AND circuit 14. If the attenuation of visible light becomes extremely large, the pulse counter 29 will be
No paper will be published without counting enough to make the circuit possible.

In this case, a separate circuit corresponding to the comparator 11, the AND circuit 14 and the alternating signal device R15 is connected to the pulse counter in order to display the visible turbidity of the test liquid as a signal that the presence of oil does not cause an F8 alarm. 29 may be followed by (2).

Figure 2 is a cutaway view of the measurement chamber 4 at the location of the quartz windows 3 and 6, the quartz windows being preferably made of gold.
In order to make the size of these quartz windows easier, a gold frame 16 is used.
．． It is preferable to take it within 17. By means of the frames 16 and 17, the aforementioned quartz windows 3 and 6 can be mounted in the borehole 18 of the measuring chamber, for example by screwing, welding or even clamping. Furthermore, the frames 16 and 17 are provided with protrusions 1 formed, for example, as strip-like fins, as shown in FIG.
9 may be provided, and these fins may make the flow n of the five directions of the arrows U of the quartz windows 8 and 6 turbulent.

FIGS. 4 and 5 show an alternative construction for connecting a quartz window to a fixed chamber, but only the upper tube wall section is shown in the projection 11. The frame 16 consists of two parts aJ, a main frame 1fla and a threaded ring 16b, which together form a hollow spherical holder, into which a spherical part 20 is attached, although airtight. It is dimensioned so that it can be rotated. A shaft 21 for rotating this spherical portion 20 is bored out. A hole 22 is formed in the spherical portion 20, and both ends thereof are closed with quartz windows 3a and 8b, respectively. If it is necessary to remove the quartz window 11 during operation, first clean the quartz window 8a, and then rotate the ball part 20 by 180° around its axis by the shaft 21, at this time removing the outer part. Finally, clean the quartz window 8b. In this way, there is no need to remove the quartz window, and the linen can be cleaned during operation.

Using only the light source 2, the photodetector 7, and the processing circuit without using the measurement chamber, another one was installed in the U'Jfr housing so that a free optical path was obtained between the light source 2 and the photodetector 7. A crime of execution is also considered. Such a test device d can be used as a free-floating device, for example, for testing open water for oil contamination and possibly radioactive contamination. If this test device Cr is placed on a float so that the photon source is submerged in water and the photodetector is above water, it will be possible to detect an oil film floating on the water surface.
This is suitable. An automatic sample collection device can be activated when there is a tip.

Figure 6 shows a device W,f;! that can test for the presence of small amounts of oil in liquids such as wastewater containing a large amount of suspended matter and solids at very high βJ. i: Show. One end of the cable 35 is attached to a cable drum 32 driven by a motor (not shown) and guided by a guide roller 86. Quartz Crow Salary 81
A metal cap 81a supporting the cable 85 is attached to the other end of the cable 85. At position 16 in the figure, a quartz glass rod 81 is located between the light source 2 and the photodetector 7. These two elements are disposed within a housing 80, which includes 11
The rod 81 is made of, for example, a plastic block and has a freely movable duct 1-30b. Furthermore, this block has a duct 80a between the light source 2 and the photodetector 7, and this duct has a 0
For maintenance purposes, block 30 is located at the top of the drawing.
As shown in the lower part of FIG. 6, which shows the lOi i river of duct l-80a at an rfi angle to hI, it can be divided along line 800. In this way, in the lifted position, the quartz glass rod 81 can be removed from the light source 2 or the photodetector 7 for replacement or cleaning, such as the distorted half of the block.

In operation, the click generator 10 controls the cable puller A or its motor at the beginning of each interval so that the cable 35 is ejected and the quartz glass rod 81 is lowered into the test body 88. . As long as the cable 85 is correctly attached to the drum and fully unwound, the quartz glass rod 81 is automatically lifted out of the liquid 35 by continued rotation of the drum. metal cap 81
When a reaches a certain value n for the proximity switch 3B, this switch generates an output 1 and this signal is applied to the four generator G, causing the light source 2 to emit ultraviolet light. ff? lI? rlill a unit 1
(dl) At the same time, the pulses generated by the photodetector 7 are applied to the processing circuit as explained in FIG. An oil film is formed, which attenuates the ultraviolet light emitted from the light source 2 and projected onto the photodetector 7. When the quartz glass shell B1 is immersed upside down for consecutive measurement periods, this film The presence of a low concentration (9) of oil in the waste water can also be detected, since an oil film of ~] is formed on the 81 and the attenuation is increased. It is only necessary to reverse the direction of rotation of the cable drum 82 in each measurement period, so that in each measurement period the quartz glass bar 31 is lowered and then raised without reversing the direction of rotation of the cable drum 32. There is a cable 85 inside the clock generator IO.
In order to detect damage to the cable drum 32, failure of the drive mechanism of the cable drum 32, jamming of the cable drum 81, etc., a time control is provided to check whether the proximity switch 88 outputs an output within a predetermined time after starting to lower the cable drum 32. Good too. Above the proximity switch 38 is arranged another near switch 39, which k 1M switch ensures that in the event of a failure of the proximity switch 88, the drive motor of the cable drum is switched off first and that the drive motor of the cable 35 is switched off. To prevent damage to the device 1 when winding is not interrupted.

A quartz glass rod suspended by a cable or wire is fff
This immersed embodiment requires only a small hole to access the liquid to be tested, and the actual test equipment, including the light source, photodetector and processing circuitry, is located away from the liquid to be tested. It has the advantage that it can be used. In particular, this makes it possible, for example, to test groundwater at very deep depths for the presence of oil through narrow well bores.

Since the test equipment is on the ground, maintenance is extremely F#j 1m. If it is not necessary to physically separate the test liquid and the sample 1liI5'+ device in this way, a round quartz plate is basically used. In order to examine liquids containing objects or solid particles, it is also possible to rotate them around an axis parallel to the stationary surface and partially immerse them. In this case, the part of the quartz disk that is outside the liquid rotates between the light source and the photodetector. In this way, the entire outer part of the quartz machine can be periodically immersed and withdrawn from the test liquid.

[Brief explanation of the drawing]

Fig. 1 is a route map of the device of the present invention, Fig. 2 is a sectional view of the measurement chamber taken along line ■-■ in Fig. 1, Fig. 3 is a plan view of the quartz window, and Fig. 4 is a diagram showing different arrangements of the quartz window. FIG. 6 is a cross-sectional view of the measurement chamber having an N section, FIG. 6 is a cross-sectional view of the measurement chamber seen from a direction perpendicular to FIG. 2, and FIG. 6 is a route map showing another embodiment of the present invention. be. 2...Light source J61a, ab...Quartz window flea...Golden tube 7,27...Photodetector 8.28...Amplifier
9, 29... Pulse counter lO... Clock generator 11... Comparison section 141... AND circuit 14a
...First human power 14b...Second human power 15...Alarm device 616a, 16b...Hollow spherical holder 16.17...Frame 18...Hole 19...Group 20...・Ball part 21...Shaft 81...Quartz glass bowl 82...
・Cable drum 88...Inspection/fZ body 35...
cable.

Claims (1)

[Claims] L Light emitted from a light source and conducted by a liquid is received by a photodetector, and this photodetector sends a measurement signal whose value increases with the intensity of the light to a processing circuit. , in a device for testing the presence of a specific substance in a liquid by means of a light source, in particular the presence of oil in water, the light source (2) emits diffused light having an ultraviolet component, and the photodetector (7) is configured to detect at least ultraviolet light. An apparatus for testing the presence of a specific substance in a liquid, which has high sensitivity and is characterized in that the processing device (9-15) outputs an alarm signal when the measurement signal becomes smaller than a predetermined value.
″1゜2 The light source (2) mainly emits waves 1 of 0.2 to 0.8 μm.
A device according to claim 1 which emits light in a range of . 8 The photodetector (7) is a light that generates a pulse train whose pulse frequency increases along with the fear of light! , and the pulses are counted by a pulse counter which is set to a first preset value at the beginning of the measurement period and outputs an alarm if the second preset value has not been reached at the end of the measurement period. The device according to claim 1 or 2 for activating the comparator circuit (4) resets the total pulse counter (9) to zero at the beginning of each measuring period and at the end of each measuring period. 1
1-14);
Said comparator circuit compares the count of said pulse counter (9) with a second preset value and sends an @ alarm if at the end of the measurement period the Δ1 number of the pulse counter (9) is less than the second preset value. Any one of claims 1 to 8 which sends a trigger signal to the load +tB!゛、The equipment shown. 5 The comparator circuit (11-14) is connected to the pulse counter (9
) is compared with the second preset 4e (and if the count is smaller than the second preset value, the AND circuit (14)
Comparison ij'j that spreads the comparison signal to the first human power (14a) of
(11) and the clock generation 'd'a (10) is the second input (16b) of the AND circuit at the end between each measurement lvJ.
The output of the AND circuit of 0 is the reporting device i′1.
I (15) Special that continued to be comatose! f'l' The device h according to claim 1 (. 6. There is a measurement pause of a predetermined quality every other measurement period, and the light source (2) is controlled by the control Jl+ of the clock generator (10).
Under the pulse counter (9), which emits light only for a period of 1iltl and which was set to the first precent value at the beginning of the measurement pause, the photodetector (7)
If the 8th preset value is reached at the end of the 11 regular pauses, the iV alarm device (15) is activated. "
[The device described in item 1. 7. The light source (2) also emits light with a long wave wave, and another photodetector (27) with high sensitivity to this wave wave;
Another processing circuit (28, 29) is provided to send another measurement signal according to the intensity of light received by the photodetector (27), and the measurement signal No. 10 is transmitted to the photodetector (27). 27) If the intensity of the light projected on the device becomes smaller than a predetermined value, the processing circuit (19-15) of the h-information device should be set to a lower sensitivity setting or the prosthesis device should not work. Apparatus 1゜8 according to claim 1 of claims 1 to 6, wherein the liquid to be examined is disposed between a light source (2) and a photodetector (7). Four metal tubes with quartz windows (816)
1) The device according to any one of claims 1) to 7. 9. The device according to claim 8, wherein the metal tube T4) has a protrusion (19) that makes the liquid in front of the stone pod (8, 6) turbulent. 10. The quartz windows (8a, 8b) are hollow spherical holders (
16a, 16b) is provided on the ball portion (20) of the Yohichi tube (4), which is airtightly fitted with the metal tube (4).
Apparatus according to claim 8 or claim 9, which is rotatable about the shirt (21) approximately tangentially relative to the base of the shirt. IL photodetector (7) detects ultraviolet components with high sensitivity into 11
The 6T part M' (a 1 ) is periodically exposed to the test liquid (88
) and then pulled out and driven. (82) between the light source (2) and the photodetector (7) P1-01λ part +; t ( The device according to claim 11, wherein al) is a quartz glass rod. 1B, the stripes (81) are suspended by wires or cables (85) that are periodically wound and unwound on a motor-driven cable drum that buys a drive unit', (a2). In front of the device described in item 11 or 12. 14 Proximity switch part FA' (31) is light source (2)
19. The device according to claim 11, wherein the device is arranged to be activated when in the correct position between the photodetector (7) and the photodetector (7).