Title:
METHOD AND DEVICE FOR MONITORING STATE OF DETECTOR
Document Type and Number:
Japanese Patent JPS60133318
Kind Code:
A
Abstract:
A fire detecting arrangement has a longitudinal fire detector having conductors separated by a substance whose resistance decreases with temperature and whose charge acceptance capability increases with temperature. The detector is supplied with a rectangular waveform swinging between +5 and -5 volts through resistors, one of which is high compared with the other. High temperature will therefore cause a greater volt drop across the detector during positive waveform portions than during negative waveform portion, the potential division effect of the unequal resistors being enhanced by the increased charging current. Contamination or damage merely decreases the resistance of the detector and the lack of charging current means that the inequality of the voltage drops during positive and negative portions of the drive waveform is not so marked. A comparator compares the voltage across the detector with different reference levels at predetermined time instants synchronised with the drive waveform to produce digital signals which are fed to shift registers to cause a "fire" or "fault" warning to be produced.
Inventors:
ARUFURETSUDO ROBAATO BURAUN
RICHIYAADO ANSONII UETON
RICHIYAADO ANSONII UETON
Application Number:
JP23144484A
Publication Date:
July 16, 1985
Filing Date:
November 05, 1984
Export Citation:
Assignee:
GRAVINER LTD
International Classes:
G01D21/00; G01K7/24; G01K15/00; G08B17/06; (IPC1-7): G01D21/00; G01K15/00
Domestic Patent References:
| JPS586139A | 1983-01-13 |
Foreign References:
| US3540041A | 1970-11-10 |
Attorney, Agent or Firm:
Toshio Yano