Method and apparatus for detecting elevator safety chain

A device for detecting a status of an elevator safety chain, the device comprising:

• an interface unit coupled with the elevator safety chain and configured to output an operating signal having a first level when the elevator safety chain is in an ON state and an operating signal having a second level when the elevator safety chain is in an OFF state;
• and
• a processing unit, including:
• memory;
• a microcontroller coupled with the interface unit;
• and
• a computer program stored on the memory and running on the microcontroller, the running of the computer program causes:
• evaluating reliability of the elevator safety chain based on a time domain characteristic of the operating signal output by the interface unit;
• wherein evaluating reliability of the elevator safety chain comprises:
• determining a number of times the amplitude of the operating signal output by the interface unit changes within a time window, wherein the time window starts at the time when the amplitude of the operating signal jumps from the first level to the second level or from the second level to the first level;
• in response to the number of changes within the time window being greater than a predetermined first threshold, determining that at least one landing door switch in the elevator safety chain has possibility of failure.