EP0418409B1 - Method and device to avoid prevailing weather effects on automatic fire alarms - Google Patents

Abstract

In addition to the fire characteristics (BKG), e.g. smoke density (RD), heat or warmth (temperature T) and flame, environmental characteristics (UKG) such as temperature (T), atmospheric humidity (F) and atmospheric pressure (L) are continuously measured and used to determine the respective compensation values with which the alarm measured values are compensated, the compensated alarm measured values being further processed to form alarm criteria. In this case, the compensation can take place in the respective fire alarm itself, or be carried out in the control centre of the fire alarm system, it being the case that in addition to the analog alarm measured value the analog measured values of the environmental characteristics are regularly transmitted to the control centre. The environmental characteristics (UKG) are measured in the region of the fire alarm. A microcomputer is used to calculate the respective compensation values therefrom with the aid of algorithms or conversion tables. <IMAGE>

Description

The invention relates to a method for taking climatic environmental influences on automatic fire detectors of a fire alarm system according to the preamble of claim 1.

In today's automatic fire alarm systems, the desirable early detection of damage fires is often bought through a high false alarm rate. This means that quick recognition is often uncertain recognition.

This problem became particularly disturbing in fire alarm systems that were equipped with many threshold detectors. In the case of them, the threshold value detector was able to tip over from the idle state to the alarm state due to a short-term malfunction or a delusion caused, for example, by a swath of smoke. This led to the triggering of a false alarm via the connected fire alarm control panel.

The disadvantages of this known system were overcome in that analog fire sensors with periodic transmission of their analog measured value were used in a microprocessor-based fire alarm center which is equipped with suitable, powerful fire detection methods. These measures have led to a noticeable reduction in false alarms. Such a fire detection system is known from DE-OS 25 33 382 and in an article in TELCOM REPORT, Volume 6, Issue 2, April 1983, pages 82-87 Passau, DE, described: J.Tussing: "Pulse detection technology sets new standards in fire protection".

In the known fire detection system, analog detector measured values corresponding to the fire parameter are transmitted to the control center and processed and evaluated there, as is done in the known pulse detection technology with the principle of chain synchronization.

Furthermore, a high false alarm rate is particularly due to the fact that the response threshold of the fire detectors is changed by long-term influences such as component aging and sensor contamination. Long-term drifts in detector sensitivity were therefore compensated for by adjusting the detector idle value, so that an almost constant detector sensitivity is guaranteed. Such a rest value tracking is described for example in DE-OS 31 27 324. When tracking the detector idle value, however, no consideration is given to the type of detector used, nor are the environmental influences acting on it taken into account.

In particular, the sensitivity of today's automatic fire detectors is changed by climatic factors, such as changes in the ambient temperature, relative humidity and absolute air pressure, which represent environmental parameters. The problem of the climatic influence on the detector sensitivity has hitherto been solved only incompletely, for example by means of temperature compensation measures in the electronic part of the detectors, ie a temperature drift of electronic components is compensated for. Influences of environmental factors, such as air humidity and air pressure, have so far only been taken into account for ionization detectors. For example, US-A-4,282,520 describes an ionization smoke detector which has two ionization chambers, a measuring chamber for the detection of smoke and a reference chamber which communicates with the atmosphere via an "air tube" (breathertube) is connected, but into which no smoke can enter. This connection rapidly compensates for the air humidity and the air pressure between the interior of the reference chamber and the surrounding atmosphere. The measured value of the ionization reference chamber is used to take into account the environmental variable, ie the measured value of the measuring chamber is compensated with the measured value of the reference chamber. In the known ionization detector, climatic environmental influences are taken into account, but no environmental parameters (air pressure, humidity, temperature) are measured and compensation values are determined from them.

A reduced detection sensitivity leads to a delayed response in case of damage fires or to the failure of the detector, e.g. in smoldering fires. An increased detector sensitivity leads to an increased response to faults and deceptive variables and thus to an increased false alarm.

It is therefore an object of the invention to provide a method and a device for fire alarm systems for this, which allows damage fires to be detected early and reliably and still reduce the false alarm rate.

This object is achieved in the method mentioned at the outset with the characterizing features of claim 1 and with respect to the device with the features of claim 8.

The method according to the invention has the advantage that the detector measured values, which are used to form alarm criteria, are cleaned of the disturbing environmental influences, the ambient temperature, the relative atmospheric humidity and the absolute air pressure in the area of the fire detector being measured and using a microcomputer with the aid of Algorithms or conversion tables the respective compensation values are calculated. It is expedient to convert the conversion tables for a respective fire detector type, for example an ionization detector or an optical smoke detector, in a climate chamber to be determined under the influence of temperature, humidity and air pressure and to be written into the designated read-only memory.

The compensation can either be carried out in the respective fire detector itself, or the compensation can be carried out in the fire alarm control panel. For this purpose, in addition to the analog detector measured values, the respective analog measured values of the environmental parameters are regularly transmitted to the control center. The compensation of the environmental parameters in the fire detector has the advantage that a rest value adjustment carried out in the control center, as mentioned at the beginning, only has to take into account the long-term influences such as aging and contamination, but not those for the individual detector types and different locations different environmental influences.

In a special embodiment of the method according to the invention, the environmental parameter temperature can be recorded with a temperature sensor, the relative air humidity with a humidity sensor and the absolute air pressure with an air pressure meter, the respective individual signals being converted into a frequency-analog signal by means of an oscillator circuit, ie into one Frequency signal, the frequency of which corresponds to the value of the sensor signal in an analog manner. The value of the respective environmental parameter and thus the compensation value are then determined from each of these frequency signals using a quartz-controlled time base counter and by means of the conversion or linearization tables.

In an expedient embodiment of the invention, the fire parameter and smoke density can be compensated with the ambient parameters temperature, humidity and air pressure in a smoke detector. In the case of a heat detector, the fire parameter heat can be compensated with the ambient parameter air pressure and / or the relative air humidity, expediently the fire parameter heat is derived from the temperature measurement for the ambient temperature.

In the method according to the invention, the compensated analog measured value or the analog measured values of the fire parameter and the environmental parameters are advantageously transmitted to the control center according to the pulse reporting method with the principle of chain synchronization, in order to be processed there accordingly.

The object of the invention is achieved with respect to a device in that a fire detector with its sensor for the fire parameter together with the sensors for detecting the ambient parameters, temperature, air humidity and air pressure forms a multi-sensor that the temperature sensor of a temperature-dependent resistor with a subsequent oscillator circuit is formed that the moisture sensor is formed by a variable capacitance with a downstream oscillator circuit, that the air pressure sensor is formed by a silicon pressure measuring bridge with a downstream amplifier and voltage-frequency converter, that the environmental characteristic sensors have a measurement data acquisition device and this a measurement variable linearization device, which is associated with at least one read-only memory, is connected downstream that the multi-sensor detector has a compensation circuit which contains the measurement signals of the fire parameter and the linearized environment parameter sizes (the compensation values for temperature, humidity and air pressure) are supplied, and that the compensation circuit is followed by a line connection which is connected to the signal line via an input / output circuit. The measurement data acquisition device, the measurement variable linearization device, the read-only memory, the compensation circuit and the line connection can be formed by a microcomputer.

• Fig. 1 eine bekannte Pulsmeldelinie mit n Meldern,
• Fig. 2 eine Pulsmeldelinie für das erfindungsgemäße Verfahren mit Multisensormeldern,
• Fig. 3 einen an das Pulsmeldesystem angepaßten Feuchtemelder und
• Fig. 4 eine Meldelinie mit Multisensormeldern mit Kompensationseinrichtung

The method according to the invention and an apparatus therefor are described in more detail below. Show

• 1 shows a known pulse detection line with n detectors,
• 2 shows a pulse detection line for the method according to the invention with multi-sensor detectors,
• Fig. 3 is a moisture detector adapted to the pulse detection system and
• Fig. 4 shows an alarm line with multi-sensor detectors with compensation device

In Fig. 1, a fire alarm system that works according to the pulse alarm principle is shown in principle. It has a central station Z to which the individual detectors M1 to Mn are connected in a chain-like manner via a two-wire (a, b) primary signal line ML. The detectors on the line are e.g. polled once a second by the control panel for its respective detector measured value by the control panel briefly reducing the line voltage to zero and then increasing it to a query voltage. The fire detectors respond in sequence with a current pulse and simultaneously switch the b-wire through to the next detector. Due to the chain synchronization principle used, the detectors of the line can be individually addressed from the control center. After each complete round, i.e. In this example, every second, the control panel compares the number of current pulses received with a target number stored in a read-only memory, which corresponds to the number of detectors connected to the detector line. A line fault can be signaled in the event of inequality.

The analog measured values to be transmitted influence the response time of the detector with the help of a timer, i.e. the duration of the current pulse. The analog measured variable is fed to the control center, which records the measured values, as a pulse modulated signal. The response times for a detector are in the range of a few milliseconds. The respective analog measured variables, which correspond to the pulse duration, are measured in the control center, for example with a counter with a quartz-stable time base, and converted into digital measured values for further processing. Thus, at the end of each transmission or polling cycle, the digital measured values of all connected detectors on a line are available in the control center. They are then sent to a further processing unit as a serial data telegram.

According to FIG. 2, a multiplicity of multisensor detectors MSM are connected to a detection line M, for example MSM1 to MSM8. This multi-sensor detector is modified so that it works like a normal fire detector can be queried for the respective measured values according to the principle of pulse signaling technology. For example, with a multi-sensor detector MSM, first the smoke density R, then the temperature T, then the air humidity F and the air pressure L are measured. In principle, this means that in a multisensor detector MSM1, a smoke detector RM, a temperature detector TM, a moisture detector FM and an air pressure detector LM are connected in a chain-like manner and emit their respective analog detector measurement values when they are queried.

FIG. 3 shows an example of a moisture detector FM which has a moisture sensor FS with a downstream oscillator circuit OSZ. The frequency-analog signal obtained in this way is measured with a measured value detection device ERF. For example, this frequency signal is switched to the input of a counter. During a quartz-stable gate time, this determines the number of positive edges of the frequency that corresponds to the relative humidity. The counter reading is cached. The measured variables are linearized in a measured variable linearization device LIN. The determined meter readings serve as addresses for linearization tables, which were stored individually for each detector for environmental parameters in a read-only memory ROM during the calibration. For the humidity detector there is a linearization table for the humidity sensor which describes the non-linear behavior between the relative humidity and the frequency. Since the detectors for the environmental parameters are individually calibrated, the linearization tables also contain information about the tolerance of the frequency-determining components in addition to the characteristic data of the specific sensor. This measure ensures that the moisture detector secondarily transmits the measured relative air humidity linearly as a pulse-phase-modulated current pulse via the line connection LA and the detection line ML to the control center Z. In this way it is achieved that in a multi-sensor detector MSM1 as it is shown schematically in Fig. 2, first the measured value for the smoke density MWR, then the measured value for the temperature MWT, then the measured value for the relative humidity MWF and then the measured value for the (absolute) air pressure MWL is transmitted to the control center Z.

In Fig. 4 it is shown using the example of a multi-sensor detector MSM1 that the compensation takes place in the detector itself. It is shown schematically there that a number of multisensor detectors MSM1 to MSMn are connected to the center Z via the two-wire (a, b) primary signal line ML. The first multi-sensor detector MSM1 is shown in more detail as a block diagram. The fire parameter smoke density RD is recorded with the smoke sensor RS. The environmental parameters are recorded with the temperature sensor TS, the humidity sensor FS and the air pressure sensor LS. A respective frequency-analog signal is generated with the help of oscillator circuits for the respective environmental parameter, which signal is measured with the detection device ERF with a quartz-controlled time base counter. The respective linearized measured values for the ambient temperature T, the relative humidity F and the absolute atmospheric pressure L are determined via a downstream linearization table LIN, to which a read-only memory ROM is assigned, and are fed as a respective compensation value to the compensation device KOM, in which the analog measurement value for the smoke density MWD is compensated. The compensated measured value for the smoke density KMWR, i.e. the measured value, which has been cleaned of the environmental influences, is transmitted to the control center Z when queried via the line interface LA. As already mentioned, it is expedient to implement the individual assemblies ERF, LIN, ROM, KOM and LA using a microcomputer µR. In the central station Z, the undistorted measured values for the smoke density KMWR detected at the reporting location are processed in a known manner for alarm generation. The invention therefore largely eliminates interferences resulting from environmental conditions, so that false alarms which arise due to environmental conditions are largely avoided.

Claims (9)

1. Method for taking into account climatic ambient influences on automatic fire detectors (M1,M2,...) of a fire alarm system, in which the analog detector measured values of the fire characteristic values (BKG), for example smoke density (RD), heat or warmth (temperature T), flame, are processed and evaluated for forming alarm conditions, ambient characteristic values (UKG), such as temperature (T), air humidity (F), air pressure (L), being used for compensating the detector measured values (BKG), characterized in that, in addition to the fire characteristic values (BKG), the ambient temperature (T), the relative air humidity (F) and the absolute air pressure (L) in the region of the fire detector are measured continuously and from these, using a microcomputer, with the aid of algorithms or conversion tables, the respective compensation values are calculated, with which the detector measured values (BKG) are compensated, and in that the compensated detector measured values are further processed for forming alarm criteria.
2. Method according to Claim 1, characterized in that the compensation takes place in the respective fire detector itself or is carried out in the central control means of the fire alarm system, the analog measured values of the ambient characteristic values regularly being transmitted, in addition to the analog detector measured value, to the central control means.
3. Method according to Claim 1 or 2, characterized in that the conversion tables for one respective fire detector type (for example ionization detector or optical smoke detector) are determined in a climatic chamber under the defined influence of temperature, humidity and air pressure and are written to read-only memories (ROM) provided for this.
4. Method according to one of the preceding claims, characterized in that the ambient characteristic value of temperature (T) is acquired using a temperature sensor (TS), the ambient characteristic value of relative air humidity (F) is acquired using a humidity sensor (FS) and the ambient characteristic value of absolute air pressure (L) is acquired using an air pressure sensor (LS), in that the respective sensor signal is converted by means of an oscillator circuit (OSZ) into a frequency signal of which the frequency corresponds to the value of the sensor signal, and in that the value of the respective ambient characteristic value and hence the compensation value is determined from each of these frequency signals using a quartz-controlled time base counter (ERF) and by means of the linearization tables (LIN).
5. Method according to one of Claims 1 to 4, characterized in that, in the case of a smoke detector, the fire characteristic value of smoke density (MWR) is compensated using the ambient characteristic values of temperature (T), relative air humidity (F) and absolute air pressure (L).
6. Method according to one of Claims 1 to 4, characterized in that, in the case of a heat detector, the fire characteristic value of heat (T) is compensated using the ambient characteristic value of absolute air pressure (L) and/or relative air humidity (F), the fire characteristic value of heat being derived from the temperature measurement (T) of the temperature sensor (TS).
7. Method according to one of the preceding claims, characterized in that the compensated analog measured values or the analog measured values of the fire characteristic values and the ambient characteristic values are transmitted to the central control means in accordance with the pulsed alarm method using the principle of chain synchronization.
8. Device for carrying out the method according to one of Claims 1 to 7, characterized in that a fire detector with its sensor for the fire characteristic value, together with the sensors for acquiring the ambient characteristic values of temperature (T), air humidity (F) and air pressure (L), forms a multisensor detector (MSM), in that the temperature sensor (TS) is formed by a thermistor with an oscillator circuit (OSZ) connected downstream, in that the humidity sensor (FS) is formed by a variable capacitance having an oscillator circuit (OSZ) connected downstream, in that the air pressure sensor (S) is formed by a silicon pressure measuring bridge with an amplifier and voltage/frequency converter (VCO) connected downstream, in that the ambient characteristic value sensors (TS, FS; LS) have connected downstream of them a measurement data acquisition unit (ERF) and, downstream of the latter, a measured value linearization unit (LIN), to which is allocated at least one read-only memory (ROM), in that the multisensor detector (MSM1) has a compensation circuit (KOM) to which the measured signals of the fire characteristic value (MWR) and the linearized ambient characteristic values (T, F, L) are fed, in that the compensation circuit (KOM) has connected downstream of it a line connector (LA) which is connected to the primary alarm line (ML) via an input/output loop.
9. Device according to Claim 8, characterized in that the individual subassemblies (ERF, LIN, ROM, KOM and LA) are formed by a microcomputer (µR).

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