CS205174B1 - Circuit connexion of ionization fire detector - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to a circuit of an ionization fire detector in which protection of a transistor is addressed.

The prior art ionization fire detectors use two ionisation chambers, a measurement and compensation chamber, or one ionization chamber and an auxiliary compensation electrode, possibly one ionization chamber and a high resistance resistor. In the above-mentioned detectors, changes in the ionization current of the measuring chamber are evaluated by a sensing transistor and a high input resistance, most often of the MOS-FET type. Due to its design, this transistor has a high sensitivity to electrostatic charges, this charge can break through the base emitter transition and destroy the transistor animation. Therefore, special measures are used when assembling and repairing said detectors. The sensing transistor has short-circuited base transition, emitter and collector. When assembling and repairing the DC, it uses a glove with an antistatic finish and electrostatic discharge to Zen.

Some ionization fire detectors are equipped with a special short-circuit switch that short-circuits the sensor transistor base and emitter during assembly, repair and cleaning.

Zd6b6 solutions of circuits of ionization fire detectors have the disadvantage that

205 174

215 17 «that they require increased manufacturing costs for manufacturing, repair and cleaning by occasionally destroying the animaoist transistor by an electrostatic field, or that they disproportionately increase the cost of mounting special short-circuit switches which, during assembly, repair and cleaning by base switching from emitters ·· animation transistor before destruction ·

These disadvantages are overcome by the connection of the ionization fire detector according to the invention. SUMMARY OF THE INVENTION The sensing transistor emlter is coupled to a common switch transducer, the switch transducer satimum is coupled to the transistor base, and the switch terminal is coupled to an external ionization camera electrode that reliably protects the transistor base from electrostatic charges. The circuitry of the ionisation detector of the fire detector according to the invention makes it possible to increase the reliability and reduce the manufacturing costs of said detectors. The wiring eliminates the possibility of destroying the sensing transistor by electrostatic charge. The switch according to the invention essentially replaces two switches.

External ionization camera electrode switch and short-circuit switch to protect the transistor.

Ha ej. 1 is an example of the connection of a single-chamber ionization detector, and FIG. 2 is an example of the connection of a two-chamber ionization fire detector according to the invention. Both figures are shown in the operating mode of the detector.

Fig. 1 shows the connection of an ionisation fire detector comprising the following main parts, an external electrode of the ionization camera 6, an internal electrode with a radioactive emitter 4, an auxiliary compensation electrode of the sensing transistor 10, the support 11, the flip-flop. The sensor of the transistor is coupled to the terminal of the switch 12, while the expensive terminal of the switch is connected to the sensor terminal 10 and the first terminal of the switch is connected to the electrode of the specific ionization chamber.

A similar embodiment is shown in Fig. 2e in that the auxiliary compensation electrode p is replaced by a compensation chamber and the radioactive emitter 2 is designed to emit into both the measurement and co-chamber. The switch 10 is arranged to expose the electronics by removing the specific ionization chamber 6 to switch it from the operating position to the short-circuiting position of the bass from the omitorom transistor 10. Shorting the base e omitorom of the transistor 10 provides protection against electrostatic charge during assembly, repair and cleaning the ionisation fire detector. The connection of the emitter of the transistor 10 and the internal electrode of the specific ionization chamber 6 ensures the function of the ionisation fire detector in operation. The common terminal 2 of the sensor transistor 10 is connected to a resistor zapoj which biases the control of the flip-flop 2, depending on the voltage variations at the base of the transistor 10.

Claims (1)

A circuit of an ionisation fire detector, which consists of a circuit detecting changes in the electrical quantities of the detector detector caused by the physical phenomena of combustion and a flip-flop, characterized in that the emitter of the transistor (10) is connected to a common terminal (5) of the switch (12). whereas the second terminal (2) of the switches (12) is the epoxy of the transistor base (10) and the first terminal (1) of the switch (12) is the epoxy 8 of the external electrode of the ionization chamber (6).