[Nicola]

Hello I would like to submit a question: test 30 meters.
I have a cronopics, software cronojump, a platform-conductance, a button homebuilt, a photocell.
  The subject starts off from rest with one foot on the platform.
I would note the following times:
1) reaction time that elapses from the start signal (I press the button) to when the foot leaves the ground (take off);
2) total time from when a signal arrives at the finish line of 30 meters when the photocells are positioned.

Problem: I press the start button, however, not part of the time because the subject has his foot on the platform then the circuit is closed. How can I resolve this issue?