SU378915A1 - METHOD FOR MONITORING THE CONDITION OF SENSORS - Google Patents

Description

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The invention relates to fire automatics.

A known method of monitoring the state of sensors, for example, an alarm, is based on sending polling pulses to a sensor and then shifting it by a predetermined time interval of the response pulse of the sensor and measuring it.

According to the proposed control method, each measurement result of the temporal shift of the response pulse of the sensor is remembered, compared with the previous one, and the comparison results are summed up over a specified time interval, and the comparison result is judged by the presence or absence of an emergency situation, and in the absence of an alarm situation, the comparison result shed.

This makes it possible to increase the reliability of monitoring the state of the sensors.

On fng. 1 shows a block diagram of a device operating but the proposed method; in fig. 2 - graphs of voltages and currents as a function of time, explaining the operation of the device; in fig. 3 - sensor, one of the options.

The smoke sensor / is connected to the receiving station 2 by a two-wire communication line 3. The receiving station 2 consists of a generator of 4 polling pulses, a selector 5 of response pulses, a differential analyzer 6, a device 7 for storing and summing the comparison results and a software device 8.

The smoke sensor / consists of a smoke detector 9, a phase shifting element 10 and a response pulse generator 11.

The shaper 4 periodically sends polling pulses through line 3 to the sensor L which sends a response pulse along the same line to the receiving station. The selector 5 selects the response pulse of the sensor and feeds it to the differential analyzer 6, which determines the time shift of the leading edge of the response pulse relative to the leading edge of the polling pulse, converts it into a digital sample, compares the result of each subsequent measurement with the previous one and outputs the comparison result to the device 7 memorizing and summarizing the results of the comparison. The summation result of the device 7 is reset by the software device 8.

When a response pulse of a sensor pulse is received during a single response pulse, the selector 5 allows the driver 4 to be allowed to send the next poll pulse.

FIG. 2 accept the following notation:

Un is the interrogation pulse voltage sent by receiving station 2 to line 3;

/ o is the current of the response pulses of the sensors;

from - the level of the response pulse of the sensor, chosen above the level of noise in the line;

The / 1-predetermined time interval by which the response pulse of the sensor shifts relative to the leading edge of the polling pulse in the absence of smoke.

During the first two polling pulses, the sensor is not affected by smoke and interference, since its response pulses are shifted by a predetermined time interval. The response pulse of the sensor to the third polling pulse arrives later than the specified time interval through the fourth polling pulse, through the + interval. The increments Ati and are determined by the differential analyzer 6. If the magnitude of each increment or their sum exceeds the level during the time interval LH G1-TQ TZ-TI, an alarm signal appears. If, however, the temporal shift of the response pulse of the sensor is continuously increasing, for example, due to an increase in the ignition voltage of the thyratron, a false fire signal does not appear, despite the fact that the time shift When smoke appears and the time shift tz increases rapidly by There is a fire alarm, i.e. the system functions normally in this case.

FIG. 3 shows one of the options for performing a smoke sensor, which consists of a radioactive isotope ionization chamber 12, a phase-shifting element — a capacitor 13, and a response pulse generator — an electrometric glow discharge thyratron 14.

When a polling pulse U arrives at the sensor through the ionization chamber 12, capacitor 13 begins to charge. When the voltage on capacitor 13 reaches the ignition voltage of the thyratron 14 on the control grid, the capacitor 13 is discharged, the thyratron turns on and abruptly increases the current in line 5. This the surge current corresponds to the instant of the appearance of the response pulse of the sensor. The time interval between the leading edges of the interrogation pulse and the response pulse of the sensor depends on the charging time of the capacitor 13 before the ignition voltage of the thyratron 14. In the absence of smoke and interference, the time constant of the chain, consisting of the resistance of the ionization chamber 12 and the capacitor 13, is chosen wherein the response pulse is shifted by a predetermined time interval from the interrogation pulse.

After the arrival of the response pulse of the sensor to the selector 5, the latter gives a signal to the shaper 4 about the termination of the interrogation impulse, a pause occurs, the sensor thyratron 14

0 is turned off and prepared for the next polling pulse.

With the appearance of smoke, the resistance of the ionization chamber 12 increases and the time shift accordingly increases.

5 between the leading edges of the polling and response pulses.

The subject matter of the invention

0 A method of monitoring the state of sensors, for example, an alarm, based on polling sensors and then shifting the sensor response pulse by a specified time interval and measuring it, characterized in that, in order to increase the reliability of the sensor status monitoring, each measurement result of the sensor response pulse remember, compare with the previous one, and the comparison results are summarized for

0 of a given time interval and the magnitude of the sum of the results of comparisons are judged on the presence or absence of a dangerous situation, and in the absence of an alarm situation the result of the comparison is discarded.

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