EP 0087308 A2 19830831 - Temperature monitoring systems.
Title (en)
Temperature monitoring systems.
Title (de)
Temperaturüberwachungssysteme.
Title (fr)
Systèmes de surveillance de température.
Publication
Application
Priority
GB 8205338 A 19820223
Abstract (en)
A temperature monitoring system, useful for example for detecting fires, comprises a cable (10) having at least two conductors (14, 16) separated by elongate temperature-sensitive means having reactance (Cs) and resistance (Rs), at least the resistance (Rs) varying with temperature. A voltage source (+V) sends a d.c. current through a resistor (R) and said resistance (Rs), thereby to generate on a line (28) a d.c. signal that is representative of the value of the resistance (Rs). Switch means (22) is operative periodically to reverse the direction of current flow through the resistance (Rs), the frequency of operation being sufficiently low that, after the change in the signal that will take place upon each reversal due to the cable reactance (Cs) the signal will revert to a steady value before the next reversal. The steady state of the signal is sampled and held (30) and compared (32) with a reference value (fixed or variable). If the steady state value exceeds the reference value, an alarm or the like can be generated.
IPC 1-7
IPC 8 full level
G08B 17/06 (2006.01)
CPC (source: EP)
G08B 17/06 (2013.01)
Designated contracting state (EPC)
CH DE FR GB IT LI NL
DOCDB simple family (publication)
DOCDB simple family (application)
EP 83300895 A 19830221