DD144188A5 - ISOTOP SMOKE DETECTOR - Google Patents

Description

2 1 3405-1-

Isotopic smoke detector

Field of application of the invention

The invention relates to an automatic fire hazard message isotope smoke detector.

Characteristic of the known technical solutions

There are known isotope smoke detectors having at least one ionization chamber, which serves as an analyzer of the air in the environment of the detector. The voltage across the electrodes of the ionization chamber is continuously monitored by a field transistor (FET) connected in parallel to this chamber between the terminals of the supply source. An example of such a circuit is described in DD-PS 86 988. The smoke detectors designed based on this circuit absorb a significant amount of current during monitoring. As a result, their number in a monitoring line and the length and the cross section of belonging to this line lines are limited. Continuous voltage monitoring in the ionization chamber of the smoke detector creates conditions for triggering false alarm signals, the cause of which may be uncontrolled electrical radio interference reaching the detector electronic circuit.

The isotope smoke detector described in CH-PS 468 683, whose structure is similar to that of the detector described above, is characterized by low monitoring current, but it is sensitive to electrical radio interference and requires the shunting of the ionization chamber with a

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additional capacity, resulting in a reduction in the performance of the ionization chamber itself and a delay in the action of the detector.

Object of the invention ..

The aim of the invention is to develop an isotope smoke detector which has no mentioned disadvantages and limitations.

Explanation of the essence of the invention

The object of the invention is to provide a reliable detector, which has a low power consumption and low susceptibility.

This object is achieved in the detector according to the invention by developing an electron circuit in which the drain terminal of the MOSFET is connected via a to the first terminal of the supply source and directly to a comparator and via a capacitor to the second terminal of the supply source, said Sure -Connection of the MOSPET is switched directly to the comparator and periodically via a resistor and an electronic switch with the second terminal of the supply source.

The comparator, however, is connected to the second terminal of the supply source and via a composite of a parallel circuit of a resistor with a capacitor RC circuit with the first terminal of the supply source, wherein connected between the comparator and the RC circuit, the control terminal of the bistable flip-flop is.

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The most important part of the gate of the detector according to the invention "ordered in the reduction of its sensitivity to electrical punk interference, by impulse operation of the signaling circuit · The current pulses of the monitoring program of the detector are much higher than any random induced in the Überwaclmngsnktion current pulses. Factor "S is influenced by the reduction of the mean value of the current consumption of the detector, thereby the monitoring line can be lengthened or the use of guide rails with smaller cross sections is made possible.

In addition, the detector can be provided with a MOSFET with a stronger gate insulation layer, which thus has a higher resistance to electrical breakdown »which increases the reliability of the detector and makes its manufacturing process easier. -

embodiment

The invention will be explained in more detail with reference to an ^A usfiihrungsbeispieles and the drawing.

The drawing shows an overview diagram of the electrical circuit of the isotope smoke detector. The detector consists of deer connected, connected to the terminals 12 and 13 of the supply source ionization chamber 24 and 15, the common electrode to the insulated gate. 16 of the MOSFEO? is connected, the drain 2 is connected via the resistor 6 to the terminal 13 of the supply source and directly to the comparator 10, via the capacitor 7, however, with the second terminal 12 of the supply source.

The Source 3 of the MOSFEQ? 1, however, has a periodic scarf tiuig on the resistor 4 and the electronic

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Switch 5 to the av / eite terminal 12 of the supply source and a permanent circuit with the comparator 10, wherein the comparator 10 with one of its terminals directly to the terminal 12 of the supply source and with the other terminal via one of the capacitor 8 and the resistor 9 composite RC circuit is connected to the first terminal.13 of the supply source. In addition, the common connection point of the electronic circuit between the comparator 10 and the RC circuit is connected to the control terminal of the bistable flip-flop 11, which is connected directly to the terminals 12 and 13 of the supply source.

The isotope smoke detector switched into a monitoring line automatically generates current pulses which are given by the electronic switch 5 during the monitoring program. A small current flows through the in-line ionization chambers 14 and 15, and through the resistor 6 recharging the capacitor 7, the capacitor 7 being discharged to some extent by short periodic pulses of the monitor program current.

Upon penetration of smoke Un the ionization chamber 14, the potential at the common for the two ionization chambers 14 and 15 electrode and the insulated gate 16 of the MOSFET 1 is changed, causing a change in the short-term voltage pulses on the source 3 of the MOSi ¹ ET 1, which appear at the current-carrying electron switch 5. After a certain value of these pulses has been exceeded, the capacitor 8 is charged in pulses, and a certain increase in the voltage at the capacitor 8 causes a change in the state of the flip-flop 11 which results from the overload.

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the monitoring status changes to the alarm status. The detector reverts to the monitoring state after the breath has disappeared in the chamber monitoring the environment, whereby a brief interruption of the supply circuit is also required.

Claims (1)

2 1 3405 - ⁶ -. - 16.10.1979 55 581/17 invention claim Isotope smoke detector, comprising at least one ionization chamber monitoring the surrounding air, the voltage of which is monitored by an insulated gate field transistor (.FET), characterized in that the drain (2) of the FET (1) is connected through a resistor (6). is connected to the first terminal (13) of the supply circuit and directly to the comparator (10) and via the capacitor (7) to the other terminal of the supply source, the source (3) of the FET (1) being connected directly to the comparator (10). 10) and also periodically via a resistor (4) and an electrical switch (5) to the second terminal (1.2) of the supply source, the comparator (10) directly to the second terminal (12) of the supply source and via a parallel connection a resistor (9) to the capacitor (8) composite RC circuit is connected to the first terminal (13) of the supply source, wherein between the comparator (10) and the RC circuit, the control terminal of a bistable en flip-flops' (11) is connected.