I require the application of an electronic stopwatch. The function to be performed is as follows: A proximity switch senses a part and sends a signal to a relay. The relay activates a stop watch. Then after some .5 seconds, one more proximity switch senses the same part( it is under rotational motion). Again a signal is sent to relay and then to stopwatch to stop the count. The stopwatch should now display the stroke time of the part, that is, the time elapsed between the two proximity switch signals. When the next cycle starts, one more signal is sent to the stopwatch to reset itself. Suggest what can be used here. I am not able to come up with any device that exactly meets my requirements. Please suggest sth.