Signal waveforms extracted from data
( Module 0 , test beam 1999 )

Each signal is sampled at a frequency of 40 MHz (i.e. one sample every 25 ns).
In order to know the signal waveform with a precision of 1 ns a time phase must be introduced between the start of the signal and the DAQ clock.

Calibration Signal Waveform

To reconstruct the calibration signal waveform, DELAY runs are used, in which a current pulse of known amplitude is sent at different times w.r.t. the DAQ clock.

Physics Signal Waveform

To reconstruct the physics signal waveform, asynchronous runs are used, in which data are collected independently of the time when the particle strikes the detector. (On the opposite, in synchronous runs data are collected only if the particle arrives in a specific time window, determined by a scintillator coincidence connected to a TDC).
In this case, the signal is originated by the e.m. shower, therefore its amplitude is not fixed as in Delay runs, but has larger statistical fluctuations. The waveform is obtained by averaging over many events.