Assignee:
Otis Elevator Company - Farmington CT
International Classification:
G01R 1900
US Classification:
702 64, 702 65, 324600, 324650, 324713, 361 911
Abstract:
A pair of terminals across a voltage to be monitored includes, in series, a resistor for developing a low voltage proportional to the high voltage to be monitored, a resistor to develop a voltage indicative of an over-current condition, and a resistance comprising a plurality of resistors which are connectable in parallel with one another, automatically, by remotely actuated switches. When the monitoring system is turned off, the resistances are all automatically set to maximum to minimize the loading on the elevator system. When the monitoring system is first turned on, a preconfiguration routine determines the correct resistance value as that which is the lowest resistance value for which an overcurrent condition does not occur, and this preconfiguration resistance value is stored for future use. Upon subsequent turn on of the monitoring system, all of the resistance values are set at the values determined during the preconfiguration routine. During normal monitoring, an overcurrent condition (that is an output from the sensor responding to the overcurrent resistor) will increase the series resistance by one increment, store the new setting for future use and provide an alarm message which may be used in any conventional fashion by maintenance personnel.