The amplitude is not important to me, however the time when the peak occurs is extremely important. So my microcontroller will have an algorithm like capture the digital values, and when 'n' digital values are same (this means the peak has arrived), store the time corresponding to the first time that digital value occured. Hence obviously, it is important that rising part is accurately digitised. This is where I am sort of confused. Following is the FFT of the signal:
As you can see, it has dominant frequency components upto 15MHz. So should my sampling frequency be greater than 30MHz?
Or should it be calculated as follows: rise time ~ 2 microseconds. Therefore, frequency ~ 0.5MHz. Hence sampling frequency > 1MHz.
Please help me out with this! Thanks!