| 摘要 |
The invention concerns a method of monitoring air flow in a fire-detection device and a fire-detection device for carrying out the method. In order to eliminate as far as possible the influence of environmental parameters, in this case in particular variations in air pressure, on the air flow monitoring system, two air flow sensors (3, 4) are provided. A differential signal, which is adjusted to bring it to zero when the fire-detection device is started, is generated from the output signals of the two air flow sensors (3, 4). The monitoring of the air flow is evaluated on the basis of the adjusted differential signal, preferably also on the basis of an adjusted summation signal which is formed from the two output signals from the air flow sensors. The fire-detection device comprises: a first detector for detecting a fire parameter in a first alarm chamber (1) to which a ventilator feeds a representative volumetric amount of the room or apparatus-cooling air via a first and second intake pipe system (25, 26); a first and a second air flow sensor (3, 4) which monitor the mass flow of fed air in the two intake pipe systems (25, 26); a differential member (5) for establishing the difference between the output signals of the air flow sensors (3, 4); a first adjusting member (8) for adjusting the differential signal to zero; an evaluation circuit (6) with a lower and an upper threshold value; and a display unit (7) which displays a malfunction in dependence on the output signal from the evaluation circuit (6). |
