I have a Signal of 3 seconds. At different times I start sampling(extract samples) . I need a word that refers to the beginning of each sampling in the signal. I thought of starting point but I am looking for a more accurate term, that sounds more scientific.
I would suggest:
You can see the phrase being used in the context you've mentioned in a discussion on apple.com, they are talking about music, but whatever you are sampling, I am sure the terminology applies equally as well:
The loop needs to start somewhere after the sample start, and the loop needs to end before the sample end.
or to be less idiomatic, you might use:
Sample start point
As used in this video, on lynda.com:
...sample start and end points...
Consider the term epoch.
Epoch specifically refers to time points or "windows" and is a term commonly used in brain imaging studies. For example, here is how epoch is used to describe the design of one study:
Each exercise run consisted of a 30-s pre-exercise epoch, ten 20-s stimulation epochs separated by ten 20-s control epochs, and a 50-s after-exercise epoch.
For your situation I wouldn't be able to comment without knowing more about what it is you are intending to do, but epoch could be used like so:
The signal was of 3 seconds duration, and sampled into epochs, each 500 ms in length.