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Fire alarms should be reliable and, even under adverse environmental conditions, they should not give false alarm or deteriorate insensitivity as a result of fouling or other influences. In addition, many materials that have to be safeguarded against fire are sensitive, and so the fire alarm has to be actuated in a very short time of just a few milliseconds. The previous way of combining various fire alarms working on different physical principles has many disadvantages. For example, fouling of optical fire alarms and the false alarm rates of systems responding to compression waves or acceleration make these types insufficiently reliable. A quick-acting and reliable fire alarm system is afforded by an acoustical device based on ultrasonic radar. An outbreak of fire heats the air in the vicinity of the fire, thus causing changes in the velocity of airborne sound. This very fast physical process causes the travel time of an ultrasonic signal passing through the heated region to be shorter than at low temperatures. Ultrasonic pulses are transmitted and the time of arrival or echo return time is measured so that any temperature rise indicating an outbreak of fire is detected.
Fire alarms should be reliable and, even under adverse environmental conditions, they should not give false alarm or deteriorate insensitivity as a result of fouling or other influences. In addition, many materials that have to be safeguarded against fire are sensitive, and so the fire alarm has to be actuated in a very short time of just a few milliseconds. The previous way of combining various fire alarms working on different physical principles has many disadvantages. For example, fouling of optical fire alarms and the false alarm rates of systems responding to compression waves or acceleration make these types insufficiently reliable. A quick-acting and reliable fire alarm system is afforded by an acoustical device based on ultrasonic radar. An outbreak of fire heats the air in the vicinity of the fire, thus causing changes in the velocity of airborne sound. This very fast physical process causes the travel time of an ultrasonic signal passing through the heated region to be shorter than at low temperatures. Ultrasonic pulses are transmitted and the time of arrival or echo return time is measured so that any temperature rise indicating an outbreak of fire is detected.
Ultrasonic fire alarms
Akustischer Feuermelder
Mantel, J. (author)
1983
8 Seiten, 3 Bilder
Conference paper
English
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Engineering Index Backfile | 1929
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