DE2327497B2 - DETECTOR FOR CHANGES IN RESISTANCE WITH A FOLLOWING ALARM DEVICE - Google Patents

Description

The main reason for this is that the detector constantly monitors itself as a whole and in the event of failure and / or change of a circuit part or circuit element issues a message. So can can not be differentiated when known, if the vibrations are fanned or stop, whether this change of state is actually due to a change in the (to be monitored) physical Size or can be traced back to the detector or its components. To check the operational readiness at most a measure comparable to the fire test described in connection with CH-PS 4 68 683 would come into consideration, im Case of the DT-AS 14 66 554 thus creating an "artificial" level by immersing the Sensor in a material sample or switching on an impedance between the terminals of the encoder. In the drawings shows

F i g. 1 a prior art circuit arrangement of a fire warning device,

F i g. 2 shows a first embodiment of a detector according to the invention,

F i g. 3 shows a second exemplary embodiment of a detector using an integrated circuit,

F i g. 4 shows a third exemplary embodiment of a knife according to the invention as a variant of FIGS. 2 and 3 arrangements shown,

F i g. 5 an interconnection of several parallel-connected, mutually and automatically monitoring individual panels,

F i g. 6 an interconnection of several in series, mutually and automatically monitoring single detectors,

F i g. 7 an embodiment of an evaluation device,

F i g. 8 an embodiment of a detector according to the invention for monitoring fill levels,

F i g. 9 shows a modification of the FIG. 8 detector arrangement shown,

10 shows a further modification of a detector according to the invention for monitoring temperatures.

In Fig. 1, a conventional detector for resistance levels, a so-called ionization detector, is shown for example. It consists of a transmitter 1 converting changes in physical quantities into resistance changes between its terminals, a threshold amplifier, an alarm device A, in this case a pair of incandescent lamps 13, 14 are switched on.

The mode of operation of the ionization detector described above can be seen from the following: After applying the operating voltage I / „wander - Due to the ionization - electrons to electrode 4, the ions to electrode 3. A current flows which results in a voltage drop across the gate resistor 6. Is the The voltage drop across this resistor 6 is sufficiently large, so the MOSFET is turned on, whereby again the transistor 9 is also turned on. As a result, relay 10 picks up and actuates the transfer contact 12. Lamp 13 lights up.

If the ionization in the ionization chamber changes, for example due to combustion gases or smoke particles, the current flow through the ionization chamber 1 or through the gate resistor 6 decreases. Below a certain voltage above the gate resistor, the MOSFET 5 blocks and the relay 10 drops and applies the lamp 14 to the operating voltage U / j.

A deterioration in the insulation resistance in the transmitter 1, the ionization chamber, or a Defect of the transistors 5 and / or 9 does not occur during normal operation of such an ionization detector Appearance and can usually only be determined during a fire test. On the other hand can through Changing the electrical parameters of the circuit will trigger a false alarm.

To remedy this deficiency, the in F i g. 1 circuit shown by means of automatic Monitoring in the form of a feedback circuit expanded. This is in the circuitry of the Fig. 2 is shown as an example. In Figs. 1 and 2, the same parts are provided with the same reference numerals.

Compared to the arrangement of FIG. 1 differs from that in FIG. 2 detector arrangement shown by means of a feedback from the output consisting of an AC element, resistor 15 and capacitor 16 of the threshold amplifier to the input of the same. This feedback is provided by the relay 10 causes the switching contacts of the resistor 15 of the 7? C element to ground potential when energized or to a voltage [/ _ which is even more negative than the operating voltage. In the non-aroused state is the mentioned resistance across the switching

45

V _s and an alarm device A. The encoder is

for example an ionization chamber. This consists of 50 contact 12 placed on U _B.

from a radioactive source 2, e.g. B. a The operation of the circuit arrangement ge

according to Fig. 2 follows from the following:

When the operating voltage U _{B is applied} , the voltage on the capacitor 16 and thus also on the terminals of the encoder 1 increases according to the exponential set2. The rate of rise is defined by the RC element 15, 16. This increase in voltage continues until the gate voltage air MOSFET is sufficient to control it. The result of this also turns on transistor 9, there; Relay 10 picks up.

The switch contact 12 of the relay 10 puts the switch-side end of the resistor 15 to ground odei

_tim to the said negative voltage U_, whereby dei

tied together. In the collector circuit of the transistor 9 there is 65 capacitor 16 via this resistor discharges a relay 10, the coil of which is a free-wheeling diode. If the voltage on the plate falls below U, it is bridged. The relay 10 has a certain value of this capacitor when switching contact 12 occurs. By means of this contact, relay 10 can start again, the charging process of the Kon

Americium 241 or a cesium IBT source, lower Dose rate. This source is on a carrier plate which also serves as electrode 3 arranged. An electrode 4 is provided opposite the radiator. Both electrodes form the Clamping the encoder 1.

The threshold amplifier Vg is constructed in two stages. It has a metal oxide field effect transistor 5, referred to below as a MOSFET, with a gate bleeder resistor 6, a drain resistor 7 and a source resistor 8, connected as a source stage. The base of the following transistor 9 is galvanically connected to the drain connection of the MOSFET 5

2

densators starts all over again. An approximately square-wave voltage with an amplitude of approximately Ui ₁ arises at the collector of transistor 9. The frequency of this voltage is essentially determined by the time constant of the ftC element consisting of resistor S 15 and capacitor 16. This voltage U ₉ , which can be tapped between the collector of the transistor 9 and ground or U _lt, provides unambiguous information about the functionality of the indicator and about changes in the ionization capacity within the ionization chamber 1.

There are essentially four different detector states that can occur:

a) The output voltage U ₉ has an amplitude of approximately Un, its frequency corresponds to the "nominal value" determined by the /? C element,

b) the frequency of the output voltage U ₉ deviates from this "nominal value",

c) the output voltage U ₉ is no longer an alternating voltage, its amplitude is approximately t / ",

d) the amplitude of the output voltage U ₉ has dropped to approximately the residual voltage of the transistor 9, and vibrations can no longer be detected.

In case a) the detector that has ionization capacity in the ionization chamber 1 is ready for operation practically does not change.

In case b), the detector is no longer 100 percent operational. Active or passive components of the indicator, its supply voltage U ₁₁ or other variables have changed that make a check necessary.

In case c) the detector is defective.

In Fa ¹ I d) the transistor 9 is turned on: combustion gases or smoke particles in the ionization chamber have caused the detector to respond.

In addition to the collector voltage of the transistor 9, the voltage U ₁₉ between the plates of the capacitor 16 can also be used to differentiate between the four operating states of the detector. This voltage U ₁₆ is also an alternating voltage with a frequency defined by the IC element IS, 16, but with a smaller amplitude than the alternating voltage that can be tapped off at the collector of the transistor 9.

In addition, the mentioned voltage U ₁₆ provides additional information that is characteristic of the functionality and responsiveness of the detector.

As mentioned above, this voltage is an approximately square-wave alternating voltage with a frequency defined by the AC element 15, 16. In contrast to the voltage at the collector of transistor 9, this voltage U ₁₀ fluctuates between the following two DC voltage levels IZ ₁ and U ₂ :

U ₁ : If the resistor 15 is connected to the supply voltage U _n , the capacitor 16 is charged via the mentioned resistor until the voltage across the gate resistor 6 controls the MOSFET 5. This voltage at the gate corresponds to a certain voltage across the capacitor, since the resistor 5, the ionization chamber 1 and the gate resistor form a voltage divider chain between U _B and ground.

IZ ₂ : After the MOSFET 5 has been turned on, the relay 10 picks up, and the resistor 15 is connected to 1 / by means of switch 12. placed. The discharge of the capacitor 16 via the resistor 15 continues until the voltage at the gate of the MOSFET 5 is no longer sufficient to control it. When this MOSFET is blocked, a certain voltage is present between the plates of the capacitor 16. This differs from the voltage level U ₁ defined above, due to the hysteresis of the threshold amplifier, in a very specific way. In the exemplary embodiment shown, this level t /., Is smaller than the level U ₁ .

The two levels U ₁ and U ₂ are a measure of the functionality and responsiveness of the detector. This can be seen from the following:

If the value of the resistor 6, the operating voltage, the response threshold of the threshold amplifier or the like changes for any reason, this has a direct effect on the levels mentioned, since the voltage divider ratio of the voltage divider chain 15, 1, 6 then also changes. Thus, in addition to the voltage at the collector of the transistor 9, the voltage U ₁₆ between the plates of the capacitor 16 can also be processed further in the manner still to be described. In the last-mentioned case, however, it is expedient not to feed the voltage f /, _e directly to an evaluation device which is usually spatially separated from the indicator, but to connect an impedance converter in between.

From the above, another major advantage of the proposed indicator becomes clear: The working point of the indicator "oscillates", so to speak, always around its area of greatest sensitivity. Changes in the dose rate of the radiation source or other, adversely affecting the Environmental influences affecting the response threshold of the detector are regulated.

Due to the mentioned oscillations, one also comes with lower dose rates of the Radiation source. This in turn makes it possible to reduce the effort involved in shielding the radiation source to drift.

A possible embodiment of a circuit arrangement for evaluating a measure of the operational readiness of the detector according to FIG. 2 representing output voltages U ₉ and U ₁₆ is shown in FIG. 7 shown.

This evaluation circuit consists of a Schmitt trigger 17, which is followed by a monostable multivibrator 18. The Q output of the multivibrator 18 is followed by a low-pass filter consisting of the resistor 19 and the capacitor 20. The voltage applied to the plates of the capacitor 20 voltage CZ ₂₀ can be read on a voltmeter 21st A voltmeter is preferably used with switch contacts actuated by the pointer and displaceable on the reading scale. If the voltage U ₂₀ exceeds or falls below defined values, the contacts are closed and, for example, alarm lamps A or the like are switched on. Schmitt triggers, monostable multivibrators and voltmeters constructed in this way are known and will not be explained in more detail.

The mode of operation of this circuit arrangement can be seen from the following:

Corresponds to the voltage at the collector of transistor 9 (Fig. 2) in terms of amplitude and frequency the setpoint (case a), the Schmitt trigger switches

509584/381

2

17 each time a certain voltage value is exceeded, which should be greater than the residual voltage of the transistor 9, through. An L signal is generated at its output, which sets the monostable multivibrator 18. The proper time of the monostable multivibrator 18 should be smaller than the period of U ₉ . The low-pass filter 20, 19 integrates this output voltage U _lH . A voltage U., _o is formed on the plates of the capacitor 20, which voltage is proportional to the mean value of U _{18 over time.} The display on the instrument 21 is a measure of the frequency of this voltage U _1S and thus also a measure of the frequency of the voltage at the collector of the transistor 9.

If the frequency of this voltage falls below or exceeds an adjustable value, one of the two contacts on the instrument 21 closed.

If the amplitude of the voltage t / ₉ does not reach the value required to switch the Schmitt trigger 17 through, the monostable multivibrator 18 remains in the idle state. The voltage across the capacitor 20 then also remains below a certain value. Then, too, an alarm is triggered by means of the contacts of the instrument 21.

Likewise, if the monostable multivibrator 18 is set continuously, it triggers an alarm if the voltage U ₉ constantly remains above the threshold voltage at the input of the Schmitt trigger 17.

In order to be able to differentiate between the two states of the detector described under b) and d), d. H. To be able to differentiate between the disturbance of the detector and the actual outbreak of fire becomes the following suggested:

A resistor is connected to the first input of an AND element 23 with the interposition of a resistor 24 and a capacitor 25 existing low pass, the Q output of the Schmitt trigger 17 connected, while the second input of the AND gate with the interposition of another Low-pass filter 26, 27 and an inverter 28 are connected to the Q output of the monostable multivibrator 18 is. In another variant, the 0 output of the monostable multivibrator 18 with the interposition of the low-pass filter 26 ', 27' to the mentioned second input of the AND element 23 be switched on. The output of the AND element 23 can activate a further alarm device 29. The two low-pass filters 24, 25 and 26, 27 are to be designed in such a way that the output signals of the Schmitt trigger 17 and of the monostable multivibrator 18, the voltages at the inputs of the AND gate 23 not enough to let this change its initial state. Further variants can be between a Schmitt trigger 29 and 30, respectively, can be connected to said low-pass filters 24, 25 and 26, 27.

The evaluation circuit described above is only to be regarded as an example. It's on that This field addressed expert using known building blocks of the analog and / or Leave digital technology, an optimal evaluation device suitable for the desired purpose to realize.

In Fig. 3 is a second embodiment of a detector according to the invention as a variant of that Circuit arrangement according to FIG. 2 shown

In this exemplary embodiment, an integrated circuit consisting of a metal oxide field effect transistor 31, a bipolar transistor 32 and a resistor 33 connected between the drain or base terminal of the MOSFET or bipolar transistor and its emitter terminal is used. Such an integrated circuit is available under the designation TAA 320 on the MariU. By using them, the structure of a detector according to FIG. 2 is particularly simple, since its output current is large enough to energize a relay 34. This detector is also provided with a device for automatic monitoring of its operational readiness. However, this differs from that in connection with the one in FIG. 2 by a different type of feedback.

The gate resistor 15 ′ is now via a switching contact 35 which can be actuated by the relay 34 connected to ground. A capacitor 36 is located between the gate terminal of the MOSFET 31 and ground.

The ionization chamber 1 lies between the gate connection and the operating voltage IZ _n .

The mode of operation of the circuit arrangement according to FIG. 3 results from the following:

Shortly after the operating voltage U _lt is applied, the MOSFET 31 is turned on, as is the transistor 32. The relay 34 is energized. The contact 35 designed as a normally closed contact separates the resistor 15 'from ground. Shortly after the operating voltage is switched on, practically zero voltage is applied to the capacitor. Due to the finite resistance between the electrodes 3, 4 of the ionization chamber 1, the voltage between the plates of the capacitor 36 increases slowly. If this voltage reaches a certain value, the MOSFET 31 is blocked, the relay 34 drops out and closes the contact 35, whereby the capacitor 36 is discharged. The relay picks up again and the processes described above are repeated. An approximately square-wave voltage CZ ₃₂ arises at the collector of transistor _{32, comparable to the voltage CZ 9} arising at the collector of transistor 9 (FIG. 2). This voltage can now be adjusted in the same way as described above by means of a FIG. 7 corresponding evaluation circuit can be further processed.

Instead of the resistor 15 'between the gate connection of the MOSFET 31 and the switching contact 35 The relay 34 can expediently be joined by a further ionization chamber. This must be encapsulated in this way ensure that no fire gases or smoke particles can penetrate into them.

Of course, this measure can be used in the case of the FIG. 2 apply circuit arrangement described. There the resistor 6 would have to be replaced by a further ionization chamber.

The use of an encapsulated and an unencapsulated ionization chamber for deactivation of certain environmental influences is state of the art and, for example, in CH-PS 2 97 463 described in detail.

Another variant of the in FIG. The arrangement shown in Fig. 3 is to use instead of resistor 15 'and contact 35 one through the relay or a suitable electromagnet, which takes the place of the Relay coil can occur to provide actuated absorber between electrode 4 and radioactive radiator 2. The absorber is pushed in between when the relay or the coil is de-energized. The condenser

J6 then discharges due to its insulation resistance by itself.

Such an absorber, which can be operated separately, can also be used to conveniently control the Sensitivity of the in the F i g. The indicators shown in 2 and 3 can be used. Forms the absorber is made in such a way that when it is introduced, the ionization capacity in the Ionization chamber more defined in the same way as in the presence of combustion gases or smoke particles Concentration changes, so can the response sensitivity of the indicator in a simple manner to be controlled.

Such absorbers can also be introduced automatically, controlled by a corresponding device take place at regular intervals. With the actuation of the absorber would have to avoid False alarms are neutralized during such a test, the actual alarm device. This can be done by switching the output of the indicator at the same time as activating the absorber take place.

F i g. 4 shows a further exemplary embodiment of the invention. The resistor between the gate connection of the MOSFET 5 and ground is replaced by a capacitor 36, and the ionization chamber 1 is connected to the operating voltage U ₁₁ via a resistor 37. Instead of the output transistor 9, there is now a Schmitt trigger formed from the transistors 38 and 39 and the resistors 40, 40a ... 43. The output voltage IZ ₃₉ can be tapped at the collector of the transistor 39. This output voltage is fed to the base of a further transistor 45 via a Zener diode 44. This transistor is parallel to the series circuit consisting of ionization chamber 1 and capacitor 36.

The mode of operation of the in F i g. 4 is shown in the following:

After the operating voltage U _{n has been applied} , the voltage is initially zero between the plates of the capacitor 36. The MOSFET 5 is blocked. The collector of the transistor 39 of the Schmitt trigger is at low potential, which is practically determined by the voltage divider ratio of the resistors 40 and 42. Due to the potential at the collector of transistor 39, transistor 45 is blocked. Its collector is approximately at 1 / _ß potential. Under normal conditions, the capacitor 36 is now charged by the charge generated in the ionization chamber 1 during the ionization. The voltage at the gate connection of the MOSFET 5 increases until it is sufficient to control the MOSFET 5. As a result, the Schmitt trigger switches over, the potential at the collector of transistor 39 rises, which in turn activates transistor 45. Due to the inherent losses of the capacitor 36, it discharges again until the voltage between its plates is so low that the MOSFET changes from the conductive to the blocked state. Then the process just described is repeated. At the collector of the transistor 39 or between the collector and emitter of the transistor 45, an approximately square-wave alternating voltage arises with the voltage in connection with the one shown in FIG. 2 shown and described embodiment mentioned properties. This voltage can be processed in the same way as described there.

In Figure 4 there is another variant of a racider illustrated with Schmitt trigger for example. If you replace the ones shown on the left with the dash-dotted lines Line consisting of transistor 45 and Zener diode 44 through a circuit arrangement at between the Zener diode 44 and the base of the transistor 45, a further resistor 46 and between If a further capacitor 47 is connected to the base and ground, the arrangement thus modified acts in a manner similar to that described above. A change in the switching state of the Schmitt trigger then causes the capacitor 47 to be charged until the transistor 45 turns on.

Another modification (not shown) of the FIG. 4 is shown circuit arrangement therein, between the electrodes 4 and the radioactive emitter 2 a lying at ground potential Auxiliary electrode, e.g. B. a grid or a pinhole to provide. That way, the unloading process of the capacitor 36 accelerated.

The following principle is common to all of the exemplary embodiments described above:

The input of the threshold amplifier is via an input variable is fed to a type of feedback circuit which determines the switching state in changes a state corresponding to an alarm state without primarily triggering an alarm. By time-defining Limbs, e.g. B. KC members, the resistor or resistors of this ÄC member by the Donors can be formed themselves, this state is canceled again. So it is about an oscillatable arrangement of the most general kind. The parameters of these oscillations are through affects active, passive or other components, or the arrangement listens under certain conditions on to swing. These vibrations, e.g. B. Frequency or amplitude, or just the determination, whether an oscillation takes place at all is

the used according to the invention to the operational readiness or functionality of the indicator to monitor automatically.

While in the embodiments described so far, so-called ionization detectors in The focus should now be on the basis of an exemplary embodiment of a detector according to a further development the invention its application for the independent monitoring of fill levels or as Overflow protection are explained. Only the insignificant differences should be noted for ionization detectors.

The same parts are shown in FIG. 8 showing an embodiment a level indicator shows, provided with the same reference numerals as in F i g. 2 or Fig. 4.

In Fig. 8, a resistor 48 takes the place of the ionization chamber. The gate resistor 6 isl replaced by a pair of electrodes 49, the transmitter. The pair of electrodes are insulated from each other ir attached to a support plate 50 and in a Behäli 51, the level of which is to be monitored, is arranges. If the liquid touches both electrodes, the electrical resistance at the terminals changes men.

The operation of the shown in Fig. 8! Arrangement is explained below.

After the operating voltage U _B has been applied, the relay 10, which is a break contact 12, is next

2 5281

13 14

has fallen off. The capacitor charges through this amplifier then becomes an alarm device

the resistor 15 on. This also increases the triggered.

Voltage at the gate connection cies MOSFET 5 until the incandescent lamp 63 switches on with a constant value instead. The normally closed contact 12 'opens to supply current, it is switched on by the switch and connects the resistor 15 to ground or a negative current U _ which is dependent on the threshold amplifier. The capacitor 16 discharges pulses controlled. For this purpose, the glow, which decreases the voltage at the gate connection, lamp via a resistor 15 with one of the Rewo, in turn, the MOSFET 5 blocks and the relay 10 actuated switch connected, which is in AbKontakt 12'via Relay 10 closes. Then the process starts again depending on the switching status of the threshold value verser. io strengthen this resistance with either one

If the resistance between the elec- trical or with the other pole of the supply voltage decreases

Troden 49 in that it connects with the liquid in U _B.

The MOSFET cannot come into contact. The mode of operation of the arrangement according to FIG. 9

pass more into the conductive state. The con- is evident from the following:

bar 12 'remains closed. The arrangement oscillates 15 after applying the operating voltage U _B switches

no longer. When dimensioning this switch, the threshold amplifier F ₅ immediately passes through and lays down

It is important to note that at the gate-to the resistor 15 is connected to U _B by means of relay 10. As a result

When the MOSFET 5 is closed and the resistance thereof becomes low, the incandescent lamp 63 lights up. this in turn

Encoder a small, to control the MOSFET has the consequence that the voltage drop at the photo

there is insufficient voltage. This can be 20 resistance 64 becomes smaller. Below a loading

by appropriate * choice of resistors 15 and correct voltage spent of the threshold amplifier

48 accomplish. It is advisable to use the resistance V _s . The relay 10 drops out. The lamp goes out. as

form as a trimming resistor to different result, the Sc'uwellwertverstärker V _s is ER-

the conductivities of the fluids calculated again, the above-described pre-

to wear. 25 gear repeats itself. At the output of the threshold value

In contrast to the ionic amplifiers described above, approximately square-wave sation detectors are created here primarily the cessation of alternating voltages, the frequency of which is caused by the Helder oscillations, which occur at practically any increase in the lightness of the incandescent lamp as well as the inertia of the circuit arrangement in the form of alternating the nature of the photoresistor is determined.
Approximately square-wave alternating voltages from 30 which are accessible at the output of the amplifier or also at, an indication of the alarm status. The alternating voltage that can be tapped at the incandescent lamp is, on the one hand, changes in the frequency, these are a measure of the functionality and the operating AC voltage is a measure of the functionality of the device.

speed and can by an evaluation circuit of the circuit arrangement shown in FIG

described type can be detected. 35 of a detector for level monitoring can be

The circuit arrangement described above by varying the encoder in a simple manner as well

for the automatic monitoring of filling levels - they for monitoring other physical quantities

can also be used as an overflow protection - use.

shows the broad field of application of the invention. One of the many possibilities is shown in FIG

underlying idea. However, it is shown as an example. It's about

indicated that with the in F i g. 8 shown filling a temperature monitoring device.

Level monitoring device of the sensors 49, 50 The photoresistor 64 takes the place of the photo resistor 64

not completely in the automatic monitoring NTC thermistor 65. In the immediate vicinity of the NTC thermistor

is involved. Although a short circuit in is a heat source 66, z. B. an incandescent lamp,

reliably detect the supply lines, but not an orderly one. In place of the incandescent lamp can also

Interruption. a heating coil that partially surrounds the thermistor

The way in which a fill level is monitored.

The giver is also responsible for determining the effectiveness of this device

Functionality and responsiveness is related to the foregoing

can be detected, is referred to below with reference to the 5 ° Fig. 9 made statements. As

In the exemplary embodiment illustrated in FIG. 9, the output voltage is also described above.

tert. voltage of the threshold amplifier V _s a measure of the

To simplify the display white, the functionality of the entire detector is

The indicator shown there is largely schematic. Finally he of the giver.

consists of an encoder 61, a Schwellwertver- 55 According to the invention vr for more V _s and the Schwellwertverstärker monitoring such detectors. "physical quantities, which downstream evaluation, z. B. one in the form of changes in resistance to the Klem-F i g. 7 arrangement shown. The encoder 61 is based on a word that responds to the named variables and uses the input device known from CH-PS 5 12 060. Under the direction. If the liquid level in the term "changes in resistance" exceeds a certain adjustable level, such containers 51 are understood to mean changes between the clamps, the intensity of the changes on the surface of the cone in which the ratio of voltage between the truncated 62 is reflected from an incandescent lamp 63 see the terminals and the light generated from the transmitter. This change in intensity is flowing or flowing into this current in a photosensitive element 64, z. B. a 65 changes.

Photoresistor, in a change in resistance in addition to the already described encoders, ionic

set, which in turn controls the threshold amplifier sation chamber, photosensitive element, hot

makes you respond. By addressing the conductors, all types of givers are of the type defined above

15 - ^ d 16

can be used, depending on which physical quantity is loaded via the cons that are parallel to them

to be detected or monitored. Thus, assistants 106 etc. can block the corresponding MOSFETs

For example, for monitoring fire gases or reindeer, as well as the corresponding output transistors

Smoke particles also work on a semiconductor basis - 109 etc., which increases their collector potential

the encoder can be used. With such known 5 all inputs of the logic L are on high Po

th detectors if their conductivity changes in potential, the transistor 49 controls through, its KoI

Dependence on certain gaseous or other lecturer potential falls to almost zero potential

Substances in the immediate vicinity of the ac- This repeats the above-described before

tive area of the detector. corridors.

The circuit arrangement shown in FIG. 5, the above-described alarm arrangement shows a parallel connection of several opposing positions, similar to the previously described one-sided, automatically monitoring individual alarms. The oscillatory arrangement is shown. The frequency of this arrangement consists of individual, each through oscillations, they can be taken in the form of electrical components framed by dashed lines, a control voltage at different points of the circuit or reference indicator / _s and three parallel-connected arrangements, z. B. at the output A _L ended detectors I ₁ , L ₂ , I ₃ and a logic L, which the logic L or at the output / ^ of the control or the output signals of the detector /, linked to I _3. Reference detector I _s , is no longer in the

All detector / _s , I ₁ , I ₂ and I ₃ are determined in the same simple manner as it is for example

Structure and correspond approximately to the case in FIG. 2 of the circuit arrangement according to FIG

shown detectors with the following differences. 20 was. The logic L is only switched over if

Instead of relay 10 in the collector circuit, the AND condition is met at its inputs.

Output transistor 9 or 109 etc. occurs in each case that is, the control or reference message

Resistor 10 'or 110', and parallel to the gate / _s initiated checking of the individual detectors I ₁

Resistance 6 or 106 etc. is a con- to I ₃ only occurs again when all these inputs

capacitors 48 or 148 , etc. The inputs of the individual indicators are checked for functionality by their output

Cators I _s , I ₁ , 1 ₂ and /, are indicated by E _s , E ₁ , E ₂ or E. ,, of a corresponding signal. Speaks

the outputs accordingly with A ₅ , A ₁ , A ₂ or A ₃ one or more of the detectors /, to I ₃ later on, see above

designated. These outputs are synonymous with the three, and the verification of the entire arrangement

valued inputs one from a transistor 49, only later one. This late onset has one

two resistors 50, 51, a capacitor 52 30 change the frequency of the output voltages

and three diodes 53, 54 and 55 existing logic L of the logic L or of the control or reference indicator

tied together. This logic represents an AND element, resulting in I _s.

its output A _L to the input E _{s of} the indicator. The output voltages mentioned can now

tors I _s is performed. The output A _{s of} the indicator / _s in the above in connection with F 2 g. 2 described

are the inputs E ₁ , E ₂ and E _{3 of} the indicators / ,. 35 and shown in Fig. 7, for example

/., and / _s connected in parallel. Evaluation device are processed.

The mode of operation of a single detector has been described above in an implementation of a detector arrangement. The interaction of the three measured F i g. 5 the control-parallel connected single detector /, up to I ₃ together or reference detector as well as the logic in the alarm with the control and reference detector I _s and the Lo- 4 ° central installed, while the individual detectors in the gik L is explained in more detail below explained. rooms to be monitored at a suitable location and

After the operating voltage U _B has been applied, the can be accommodated. The low resistance outputs voltage between the plates of the capacitors of the transistor circuits used allow 48 and 148 zero. The MOSFETs 5 and 105 are to be used with relatively long lines. Given blocked. At the collectors of the transistors 9 and 45, the output of each individual detector with a 109 is approximately the voltage U _B. The voltage at the additional collector-base stage for the purpose of further at the output A _{L of} the AND element and thus also lowering the output impedance is provided by the voltage at the electrode 2 of the ionization ends. The other alternative, in which to be monitored chamber 1, is almost zero. Due to the fact that the space only has an ionization chamber to in-charge the capacitor 116, a current 50 flows stall and the remaining parts of the circuit in through the ionization chamber 101 to summarize the voltage at the control center, prohibits itself because the gate of the MOSFET 105 increases, until it switches through the large output impedance of ionization. The mers also switch in a corresponding manner. The latter applies in the same way to those in the MOSFETs of the remaining detectors I ₂ and / "through. F i g. 2 to 4 shown detectors.
As a result, the output transistors 109 etc. switch. 55 It can be expedient for certain applications. When all inputs of the logic are low, the functionality of the detector is in the potential, the transistor 49 blocks the logic. The room monitored by him is to be monitored directly (at least qualitatively, the potential at the electrode 4 of the ionization cam- tative). For this purpose each mer 1 grows. A current flows through the ion detector output of an indicator lamp K ₁ , K ₂ , K ₃ zugesationskammer 1, which in turn orders an increase in the 60, which results, for example, between the collector voltage at the gate of the MOSFET 5. gate of the respective output transistor and ground This controls through what is in turn switched. These lamps are expediently the result of the transistor 9 being switched on. The gallium arsenide light-emitting diodes, which are characterized by potential at the electrodes 104 etc. of the ionization, have extremely low power requirements and thus on chambers 101 etc. of the individual alarms / until I ₃ drops 65 only insignificantly load the circuit. Self-sale almost zero potential. The flow of current through this ionization chamber can also stop in the alarm center. To be installed between gate indicator lights,
and ground-switched capacitors 148 etc.

A reporter's actions are of course not limited to those shown in FIG. 5 illustrated circuit arrangement, but can also be used in the circuit arrangements of FIGS. Realize 2 to 4.

Instead of installing the control or reference indicator in the alarm center, it can also be used to monitor a room. However, it is advisable to arrange the mentioned detector I _s , as described above, in the control center, where it is exposed to the same environmental influences as the rest of the detectors, with the exception of combustion gases or smoke particles.

In Fig. 6 shows an exemplary embodiment of a detector made up of several individual detectors connected in series and mutually and automatically monitoring. The individual detectors are labeled I ₁ , I ₂ and A _1. Their structure corresponds to that of the detector according to FIG. 4. Identical parts are shown in FIGS. 4 and 6 are provided with the same reference numerals.

An amplifier stage, formed from a transistor 56 with a collector resistor 57 and a base resistor 58, is connected upstream of the ionization chamber 1. The base resistor 58 is bridged by a capacitor 59. This serves to filter out any interference signals. The counter electrode 4 of the ionization chamber is connected to the collector of the transistor 56, the other end of the ionization chamber 1 is at the input of the threshold amplifier formed from the transistors 5, 38 and 39. The resistor 6 and a capacitor 60 are located between its input, the gate of the MOSFET 5 and ground. The threshold amplifier has two outputs / 4, and _X. A _x is via the series circuit of a Zener diode 61 and a resistor 62 to the collector of the transistor 38, ~ Ä _X is directly connected to the collector of the transistor. 39

To the output A of the detector I above-described _{x x} is the input £., An additional detector /., Connected at the output of A., The input E ₃ connects a third detector Z _1, the output of Z ₃ to the input E _{1 of} the first detector / is connected. The two detectors /., And /., Have the same structure as the detector / ,, but with the detector /, the series circuit formed by the Zener diode and the resistor is connected to the collector of the last transistor, i.e. the transistor, the at /., the transistor 39 corresponds to the detector I ₁ , connected.

The mode of operation of the circuit arrangement according to FIG. 6 is explained below. After the operating voltage U _n has been applied, all MOSFETs are initially blocked, and the counter-electrodes of the ionization chambers are approximately at zero potential. The outputs A _x and A ₂ are at approximately U _B potential. The transistors in the input stages of the indicators I ₂ and / ₃ are turned on. The transistor 56 in the input stage of FIG. 7 is blocked due to the different coupling to the indicator I _3. The counter electrode 4 of the ionization chamber 1 is at approximately i7 _fl potential. As a result, the voltage at the gate of the MOSFET 5 increases. When a certain voltage value is reached, the MOSFET 5 switches through, whereupon the Schmitt trigger connected to it also tips over. The voltage at the collector of transistor 38 (= voltage at output A _x ) drops to zero. This decrease causes the input transistor of the indicator /. ,, to be blocked, which in turn causes the corresponding input transistor in the detector /., To be blocked. As a result, the counter electrode of the ionization chamber of this Meider /., Is connected to the operating voltage. The capacitor, which is parallel to the gate of the MOSFET, charges up and controls the MOSFET through. At output Z ₃ of detector I ₃

ίο is now approximately [/ fl potential, which in turn blocks the transistor 56 of the input stage of the first detector I _1. The capacitor 60 discharges through the resistor 6, the MOSFET 5 blocks, at the output Λ, is again approximately! //, - potential. Repeat it

the operations described above. The circuit arrangement consisting of the three detectors / to I ₃ represents - similar to that in FIG. 5 arrangement shown - an oscillatable structure.

In the case of FIG. 6, a detector switches the quasi

subsequent detector, softer in turn the turns him on. The output signal of this chain is inverted and thus switches the first detector in the chain, which in turn switches off the next detector. With switching off of the last detector in this chain, the first is switched on again, and so on.

The voltage that can be tapped at any input and output is a measure of the operational readiness or usefulness of all series-connected th detector and can be processed further in the manner described above.

In the circuit arrangements of FIG. 5 and 6 have been made for the sake of clarity illustrates the parallel connection or series connection of three individual detectors. The invention is of course not limited to this number.

In the case of the parallel connection shown in FIG. 5, the maximum number of individual alarms 7 that can be connected in parallel is practically limited only by the load capacity of the output stage of the alarm I _s . AND gates with almost any number of inputs are either directly commercially available as monolithic integrated circuits or can be easily built from such.

In the case of FIG. 6, the maximum number of individual detectors that can be connected in series is used practically no upper limit set. It should be noted, however, that the serial switching is so takes longer, the more individual detectors are interconnected.

For the last-mentioned circuit arrangement, that shown in FIG. 5 also applies. Even here each of the outputs can be connected to an indicator lamp (gallium arsenide light-emitting diode), in order to be able to qualitatively check the operational readiness directly on the spot.

The interconnection of several individual detectors is of course not limited to the Detectors for fire gases and / or smoke particles described in detail here. That of the design of the The invention is based on the principle of interconnecting several individual detectors to form an oscillating arrangement, can also be used without further ado for detectors with a transmitter other than an ionization chamber is used.

In addition 6 sheets of drawings

Claims (27)

Patent claims: 1. Detector for changes in resistance. Consists of at least one change of physical quantities in resistance changes, at least one threshold amplifier connected to the sensor, an alarm device connected downstream of the threshold amplifier and means for checking the operational readiness and functionality of the detector, which simulate changes in resistance between the input terminals of the threshold amplifier, characterized in that said means comprise a feedback arrangement which acts from the output of the threshold amplifier (V _s ) on its input, and that the Alann device (A) connected downstream of the threshold amplifier (V ₅ ) comprises means for detecting the amplitude and / or frequency of the threshold amplifier output voltage. 2. Detector according to claim 1, characterized in that the feedback arrangement is designed and arranged such that at the input of the threshold amplifier (V ₅ ) , depending on its switching state, the threshold amplifier responding resistance changes are generated, which in turn, the feedback between input and output of the threshold amplifier (V _s ) . 3. Detector according to claim 1 or 2, characterized in that the feedback arrangement consists of an RC element (15, 16). 4. Detector according to claim 3, characterized in that the RC element (15, 16) by means of a from the output of the threshold amplifier operated switch (12) can be switched on. 5. Detector according to claim 3, characterized in that one terminal of the transmitter (1) to the input of the threshold amplifier (V _s ), the other terminal of the transmitter (1) via a capacitor (16) to one pole of the supply voltage ( U _B ) of the threshold amplifier is connected so that the so-called other terminal of the transmitter is connected via a resistor (15), depending on the switching state of the threshold amplifier, either to the aforementioned one pole or to the other pole of the supply voltage (U _B ) of the threshold amplifier and that a resistor (6) is provided between the input and one pole of the supply voltage. 6. Detector according to claim 3, characterized in that one terminal of the transmitter (1) is connected to the input of the threshold amplifier (V _s ) and the other terminal of the transmitter is connected to one pole of the supply voltage of the threshold amplifier (V _s ) , that between the input of the threshold amplifier (V _s ) and the other pole of the supply voltage is a capacitor and that parallel to the capacitor (36) a resistor (15 ') can be switched on by means of a switch (35) operated by the output of the threshold amplifier. 7. Detector according to claim 4, 5 or 6, characterized in that the switches (12, 35) are electronic Switches, preferably toggle stages, are. 8. Detector according to claim 3, characterized in that between the input of the threshold amplifier (V _s ) and the one pole of the supply voltage (U _B ) of the threshold amplifier, a capacitor (36) and a series circuit between said input and the other pole of the supply voltage is connected from the transmitter (1) and a resistor (37) and that a switch (45) actuated by the output of the threshold amplifier is provided between one pole of the supply voltage and the connecting line between the transmitter (1) and said resistor. 9. Detector according to claim 3, characterized in that a flip-flop (38 ... 42) is provided between the output of the threshold amplifier (Vς) and said switch (45). 10. Detector according to claim 8 or 9, characterized in that the switch (45) is an electronic one The switch is connected to the output of the flip-flop via a Zener diode (44) is. 11. Detector according to claim 1, characterized in that that the encoder (1) is part of the feedback arrangement. 12. Detector according to claim 1 or 11, characterized in that the transmitter (1) is a photosensitive Element (64) is illuminated by means of a light source (63) as a function of the physical quantity to be monitored will. 13. Detector according to claim 1 or 11, characterized in that the transmitter (1) is a temperature-sensitive Resistance element (65) and that a heat source (66) for generating changes in resistance between the terminals of the resistance element (65) is provided. 14. Detector according to claim 1, characterized in that several individual indicators (Z ₁ , I ₂ , I _x ) are interconnected to form a chain of mutually monitoring indicators. 15. Detector according to claim 14, characterized in that a control indicator (Z ₅ ) is provided, which is followed by at least one further individual indicator (Z ₁ ...). 16. Detector according to claim 15, characterized in that the control indicator (I _s ) at least two parallel-connected individual indicators (Z ₁ ...) are connected downstream. 17. Detector according to claim 16, characterized in that the interconnection of the Individual indicators is designed and arranged such that, based on the response of a Individual indicator, this causes the remaining individual indicators to respond, and that a Logical circuit (L) is provided, which is used after all individual indicators have responded the parallel connection to put said first indicator in its initial state. 18. Detector according to claim 16, characterized in that the output of a first individual indicator (Z ₁ ) is connected to the input of the subsequent individual indicator (Z ₂ ), the output of which is connected to the input "of the third individual indicator, and that the output de : last indicator in the chain with the interposition of a 180 ° phase rotation direction on output of the first individual indicator (Z ₁ ) connected to the atmosphere to be monitored • ^st - stands. The output of the threshold amplifier is with 19. Detectors connected to one or more of the alarm devices. If Proverbs 1 to 18 changes, characterized in that the evaluation device for alarm signaling of the visible or invisible combustion output of the threshold amplifier (V _s ) is displayed, for example, by the presence of the evaluation device, this is expressed in a change in the inferred . electrical resistance between the terminals 20. Detector after one or more of the anions of the ionization chamber. This change in resistance Proverbs 1 to 18, characterized in that again has the response of the Schwellv / ertverdie Evaluation device zi'r alarm transmission to an IO amplifier result, which then the alarm device terminal of the encoder (1) is connected. tion triggers. 21. Detectors according to claim 19 or 20, the disadvantage of these facilities is that they characterized in that the Auswertervorricbtung have a low sensitivity, so Frequency and / or an amplitude measuring device, for example in the case of fire alarm devices has processing. »5 smoldering fires are not always recorded in time 22. Detector according to claim 21, characterized thereby. Increasing the response sensitivity indicates that limit value reporting devices are usually not possible, since such measures considerably increase the risk of false alarms provided for amplitudes and / or frequencies.
are. Another disadvantage of the known devices is 23. Detectors after one or more of the above 20 to see that they - if at all - with Attached claims, characterized by very complex, mostly separately operable over-the-top, that the giver (1) changes to physical monitoring devices are provided. So will beilischen Quantities in changes in resistance, for example, in the case of the above-mentioned fire alarm implements its terminals. device whose functionality is thereby 24. Detector according to claim 23, characterized in that there is a check in the room to be monitored indicates that an ionization fire test is being carried out on the transmitter (1). chamber is. Another from CH-PS 4 68 683 25. Detector according to claim 23, characterized in that the fire warning device is known and has a device indicates that the transmitter (1) is a smoke particle to check its functionality and / or fire gases is more appealing, is switched on by means of a separate switch Semiconductor sensor is. Feedback process initiated, which between 26. Detector according to claim 23, characterized in that the input terminals of the threshold amplifier indicates that, in particular for monitoring, causes a change in resistance or current, of fill levels, the transmitter (1) controls a light-sensitive which controls the threshold amplifier, which Liches element (64) is. 35 in turn the downstream alarm device 27. Detector according to claim 23, characterized thereby. Another switch is used to draw the sample, that, in particular for monitoring alarm ended again, the fire alarm device is back of temperatures, the transmitter (1) on temperature ready for operation. sensitive resistance element (65) is, while this known device for a heat source (66) is assigned. 4 ° Checking the operational readiness with relative can be realized by simple means, it has the serious disadvantage that only through a deliberate external influence recognizable error will. 45 It is the object of the invention to create a detector of the type mentioned at the beginning, which has the described There are no disadvantages to doing without The invention relates to a detector for external influence constantly on its functional Changes in resistance, consisting of at least readiness and functionality checked a change of physical quantities in 50 and at the same time through simple structure and Resistance changes converting sensor, min- high response sensitivity at the highest possible at least one threshold reliability associated with the sensor. value amplifier, one of the threshold value amplifier This object is achieved according to the invention with a detector of the connected alarm device and means of the aforementioned type by checking the operational readiness and functionality that the means mentioned ensure feedback capability of the detector, which resistance change arrangement, which from the output of the threshold between the terminals of the threshold amplifier acts on its input, include simulating kers. and that the alarm device connected to the threshold amplifier means for the detection of Amz. B. fill level of a container, presence of 60 plitude and / or frequency of the threshold amplifiers-combustion gases or smoke, mist, etc., are a series of ker output voltage includes,
made known by institutions. On the basis of a counterpart known detector arrangements, with so-called fire warning devices, such as the physical variable to be monitored is described in CH-PS 4 37 056, according to z. B. The presence or absence of a certain resistance between the terminals of the sensor on which this type of detector is based is explained: the right material, the oscillations of an Os-To the input of a threshold amplifier is stimulated or interrupted (DT-AS 14 66 554 an ionization chamber connected, which with or DT-PS 16 16 280), the invention differs