A mass spectrometer is disclosed comprising a Time of Flight mass analyser comprising an ion detector comprising an Analogue to Digital Converter. Signals from the Analogue to Digital Converter are digitised and the arrival time and intensity of ions are determined. The arrival time T0 and intensity S0 of each ion arrival event is converted into two separate intensities S(n),S(n+i) which are stored in neighbouring time bins T(n), T(n+1).