RU2224293C1 - Fire alarm with auto-testing means - Google Patents

Abstract

FIELD: fire alarms, particularly optic-electronic fire alarms. SUBSTANCE: fire alarm for fire detection into enclosed space with auto-testing means has transmitter and receiver. Transmitter comprises radiation source and generator of main impulse signal. Receiver has signal amplifier, decision circuit, additional channel for information signal, which may imitate change in optical medium density between transmitter and receiver by forming periodic sequence of impulse having stepwise amplitude. EFFECT: increased efficiency by prevention of failures associated with time oscillation of emitting optical signal due to outer and inner effects. 2 cl, 1 dwg

Description

 The generation of a fire warning signal is based on recording changes in the level of optical radiation between the transmitter unit and the receiver unit. The level of the optical signal in case of fire is reduced due to its scattering on smoke particles.

 When developing fire detectors, the main problem is the problem of identifying the causes of a decrease in the optical density of the medium. These can be both external factors and internal ones.

 External factors include a change in the density of the medium due to the appearance of dust in the room. To distinguish dust from smoke, temporal indicators are used, i.e., a change in optical density over time. It is believed that dust appears more slowly than smoke, therefore, a fire signal is generated if the density of the medium changes within 10-15 seconds.

Internal factors include the stability of the parameters of the signal emitted by the transmitter unit. So when the temperature in the room changes from minus 30 to +55 ^o С, the radiation intensity can change by 30-40%, and the detector threshold is 30 to 50% of the signal level change. To reduce the effect of temperature in the transmitter unit, a thermal compensation circuit is used. Many well-known detectors (for example, System Sensor 6424) are equipped with one or another thermal compensation circuit.

 However, there is another problem in the development of fire detectors. This change in the parameters of the radiating element itself is rare, but its parameters can change over time, which leads to instability of the radiation level of the transmitter signal.

 The closest solution to the proposed can be considered a device according to the patent of the Russian Federation 2173887, MPK G 08 B 17/10. This device controls the change in the radiation intensity of two sources and the sensitivity of two photodetectors, depending on the internal operating conditions of the devices. For this, the detector contains a pulse generator with antiphase outputs connected to the radiation sources of two optocouplers. The outputs of the photodetectors of the optocouplers are connected to the inputs of the measuring transducer, which is an arithmetic device, the third of the inputs of which is connected to the output of the pulse switch, and the output of the arithmetic device is connected to the output stage.

 The disadvantage of this device, as well as other known devices, is the lack of control over the parameters of the entire path of formation, transmission and reception of optical radiation, which can change with changing environmental properties (for example, temperature). So, in the above device, both sources will equally change their intensity with a change in the temperature of the medium, and the resolver will not be able to determine this. The presence of two radiation sources and two photodetectors of the signal complicates the design of the device, but does not completely solve the problem of taking into account external factors.

 The objective of the proposed solution is to increase the efficiency of the fire alarm device by eliminating errors associated with temporary fluctuations in the optical signal due to the influence of both internal and external factors.

 To solve this problem, a fire detector with automatic testing, containing a transmitter, which includes a radiation source and a pulse generator of the main signal, and a receiver, which includes a signal amplifier and a decision circuit, is equipped with an additional channel of the information signal, which is designed to simulate optical changes density of the medium between the transmitter and receiver. For this, it forms a periodic sequence of pulses with a step-changing amplitude.

 The information channel on the transmitting side contains a temperature measuring unit, a mixer, a control unit, a control unit for the level of the emitted signal and an information signal generator, and on the receiving side it includes an information signal decoder and an amplitude change determination unit.

 The introduction of new blocks allows you to control all the processes in the receiver and transmitter, including changes in the internal factors of individual blocks, and this ensures the exclusion of all factors affecting the monitored signal, except for the state of the environment.

 The drawing shows a block diagram of the proposed device.

 The fire detector comprises a transmitter unit and a receiver unit. The transmitter unit includes, in addition to the traditional main signal generator 1 and signal emitter 2, an information signal generator 3, a mixer 4, a temperature measuring unit 5, a control unit 6 and a control unit for the level of the emitted signal 7.

 The output of the temperature measuring unit 5 is connected to the input of the control unit 6, which generates a signal depending on the temperature of the transmitter unit and gives it to the input of the information signal generator 3. The control unit 6 also generates test cyclic sequences for the level control unit 7. Signals from the outputs of the information generators 3 and the main signal 1 are fed to the mixer 4 and then to the emitter 2. The output of the level control unit 7 is connected to the second input of the emitter 2.

 The receiver unit contains a radiation amplifier 8, an information signal decoder 9, an amplitude change determination determining unit 10, and a decision circuit 11.

 In this case, the outputs of the amplifier 8 are connected to the decoder 9 and the decision circuit 11, and the signals from the output of the decoder 9 are sent to the amplitude change determination unit 10 and to the decision circuit 11, which, according to the analysis of the received signals from the blocks 8, 9 and 10, gives a fire alarm .

 The device operates as follows.

 The transmitter emits the main signal, which adds information about the temperature of the transmitter unit and test cyclic sequences with variable amplitude from maximum to minimum and vice versa, characterizing the amplitude parameters of the radiating element of the transmitter unit.

 The receiver first amplifies the incoming signal from the transmitter. The amplified signal is fed to the decision circuit 11 and to the decoder 9. The decoder extracts information about the temperature of the transmitter unit and transmits it to the decision circuit 11, which stores information about a possible change in the radiation amplitude depending on the temperature, which is taken into account by the decision circuit 11. Also from the decoder information on the test cyclic changes in the amplitude of the emitted signal transmitted by the transmitter unit is supplied to the unit for determining changes in amplitude 10. The amplitude change determination unit 10 compares the incoming signal with the available data from the results of the previous test cycle of the signal amplitude change and transmits the comparison results to a decision circuit to take into account the possible change in the signal amplitude as a result of its change due to internal factors of the transmitter emitter of the transmitter unit or internal factors of the amplifier of the receiver unit .

 Since the test cycles for changing the amplitude of the emitted signal are performed more than 10 times more often than the average measurement of the parameters of the optical medium between the transmitter and the receiver, the change in the level of radiation from the transmitter or the properties of the amplifier in the receiver due to the influence of internal factors is monitored and taken into account scheme.

 In this case, there is no feedback between the receiver unit and the transmitter unit.

 Thus, continuous automatic testing is carried out, simulating a change in the optical density of the medium taking into account the possible influence of internal factors of the transmitter unit and the receiver unit, as well as the transmission of information about the temperature of the transmitter unit, which allows you to control all processes occurring both in the transmitter unit and in the receiver unit , and increases the efficiency of environmental control between the transmitter and receiver, since with this control scheme all factors affecting the formation, radiation, etc. signal eat except of the environment.

Claims (2)

1. A fire detector with automatic testing, comprising a transmitter, which includes a radiation source and a pulse generator of the main signal, and a receiver, which includes a signal amplifier and a decision circuit, characterized in that it is equipped with an additional channel of the information signal, which is on the transmitting side includes a temperature measurement unit, a mixer, a signal conditioning unit depending on the temperature of the transmitter unit and generating test cyclic sequences, a level control unit the emitted signal and the information signal generator, and on the receiving side it includes an information signal decoder and an amplitude change determination unit by comparing the amplitude of the incoming signal with the available data from the results of the previous test cycle, while the output of the temperature measuring unit is connected to the input of the signal forming unit depending on the temperature the transmitter unit and the formation of test cyclic sequences, the first and second outputs of which are connected respectively to the input of the generator An ora of the information signal and with the input of the control unit for the level of the emitted signal, the first and second inputs of the mixer are connected respectively to the output of the generator of the main signal and the output of the generator of the information signal, and two inputs of the emitter are connected respectively to the output of the mixer and the output of the control unit for the level of the emitted signal, the outputs of the signal amplifier connected to the inputs of the decoder and the decision circuit, the outputs of the decoder are respectively connected to the input of the unit for determining the change in amplitude by comparing the amplitude Udy signal supplied from the data available from the previous cycle test results and the second input of a decision circuit, the third input of which is connected to the output of detecting the temperature changes by comparing the amplitude of the input signal with available data from previous test cycle results. 2. The fire detector according to claim 1, characterized in that the information signal generator is configured to generate a signal in the form of a periodic sequence of pulses with stepwise decreasing amplitude, simulating a change in the optical density of the medium between the transmitter and the receiver.