Method for identifying interference object in scatter volume of optical fire detector and optical fire detector
View Patent ↗An interference object is identified in a scatter volume of an optical fire detector, which operates according to the scattered light principle. To achieve a higher level of interference protection using a simple structure in a compact fire detector, a common scatter volume is used instead of separate scatter volumes.
1. A method for identifying an interference object in a scatter volume of an open optical fire detector which operates using at least two scattered light arrangements, comprising:
converting measured radiation to scatter signals from a common scatter volume;
evaluating the scatter signals, by comparison with one another, to identify a position of an interference object by determining a quotient of the scatter signals and comparing the quotient with lower and upper limit values,
wherein each scattered light arrangement includes a transmitter and a receiver and in each scattered light arrangement at least one of a transmit characteristic of the transmitter and a receive characteristic of the receiver is essentially of the Lambert type and a main transmit direction of each transmitter and a main receive direction of each receiver are parallel.
2. The method as claimed in claim 1 , wherein the scattered light arrangements differ from one another at least in arrangement of at least one optical component.
3. The method as claimed in claim 2 , wherein a first transmitter and a receiver form a first scattered light arrangement and a second transmitter and the receiver form a second scattered light arrangement.
4. The method as claimed in claim 2 , wherein a transmitter and a first receiver form a first scattered light arrangement and the transmitter and a second receiver form a second scattered light arrangement.
5. The method as claimed in claim 2 , wherein a plurality of transmitters and a plurality of receivers are used.
6. The method as claimed in claim 5 , wherein the transmitters emit radiation at different wavelengths.
7. The method as claimed in claim 6 , wherein said evaluating of the scatter signals comprises:
recording a pattern of the quotient over time; and
comparing the pattern that has been recorded with known patterns.
8. The method as claimed in claim 1 , wherein a first transmitter and a receiver form a first scattered light arrangement and a second transmitter and the receiver form a second scattered light arrangement.
9. The method as claimed in claim 1 , wherein a transmitter and a first receiver form a first scattered light arrangement and the transmitter and a second receiver form a second scattered light arrangement.
10. The method as claimed in claim 1 , wherein a plurality of transmitters and a plurality of receivers are used.
11. The method as claimed in claim 10 , wherein transmitters emit radiation at different wavelengths.
12. The method as claimed in claim 11 , wherein said evaluating of the scatter signals comprises:
determining a quotient of the scatter signals; and
comparing the quotient with lower and upper limit values.
13. The method as claimed in claim 12 , wherein said evaluating of the scatter signals comprises:
recording a pattern of the quotient over time; and
comparing the pattern that has been recorded with known patterns.
14. An optical open fire detector, comprising:
a detection unit, operating according to scattered light principles by converting measured radiation to scatter signals from a common scatter volume, having at least three optical components including at least one transmitter, having a transmit characteristic essentially of the Lambert type, and at least one receiver having a receive characteristic essentially of the Lambert type and a main transmit direction of each transmitter and a main receive direction of each receiver in parallel; and
an electronic evaluation unit including a programmed processor, connected to the detection unit, evaluating the scatter signals, by comparison with one another, to identify a position of an interference object by determining a quotient of the scatter signals and comparing the quotient with lower and upper limit values.
15. The optical open fire detector as claimed in claim 14 , wherein a first transmitter and a receiver form a first scattered light arrangement and a second transmitter and the receiver form a second scattered light arrangement.
16. The optical open fire detector as claimed in claim 14 , wherein a transmitter and a first receiver form a first scattered light arrangement and the transmitter and a second receiver form a second scattered light arrangement.
17. The optical open fire detector as claimed in claim 14 , wherein detection unit includes a plurality of transmitters and a plurality of receivers.
18. The optical open fire detector as claimed in claim 17 , wherein the transmitters emit radiation at different wavelengths.
19. The optical open fire detector as claimed in claim 18 , wherein said electronic evaluation unit further includes a storage storing a pattern of the quotient over time and the processor compares the pattern stored in the storage with known patterns.