Method for determining the time difference between two events recorded with asynchronously running timers in different devices

The method involves connecting first and second devices (1,2) such as motor controller and separate voltage measurement module together via serial communication link. A first time of occurrence of second event in second apparatus is detected and stored. A synchronization message (4) is generated in first device, if first event is detected in or from first apparatus. A second time of synchronization message arrival is stored in second device. The delay time difference between message generation and message arrival detection is determined based on time difference between events. Independent claims are included for the following: (1) system for determining time difference between events recorded in or from first device, and second event to be detected in second device; and (2) computer program for determining time difference between events recorded in or from first device, and second event to be detected in second device.