sensor activated time measurement

I am trying to measure the time for an object to reach the bottome of glass container. The objective is to see how the shape of the object affects the drop time. The drop time will be about 200-300ms.
What kind of sensors can I use?
Where can I get the time measuement circuit?
Thanks
Ravi

I would use light beam sensors for the start and stop signal input to a digital stopwatch. Small distance light beam sensors are very common and cheap but for bigger ( more than a few mm) distances you might have to dig through a parts catalogue for suitable components to make one.

You might be able to adapt a cheap digital stopwatch if you can get at the start / stop button contacts.
Or you could get a digital panel mounting timer and use that, just make sure it has a millisecond setting.

Of course, you could also build a timer/ stopwatch but it almost certainly would be more expensive than the ready made ones :wink: