Abstract: A mass analyzer system uses a simultaneous mode electron multiplier detector which outputs both a pulse count and an analog signal. Depending on the ion flux intensity, the signals define a pulse count only region in which the pulse count only signal is valid, an overlap region in which both the pulse count and analog signals are valid, an analog signal only region in which only the analog signal is valid, and a neither analog nor pulse region in which neither signal is valid. The system produces a separate flag for each region. When a mass spectrum is scanned, for each dwell the pulse count and analog data are recorded together with their associated flag and are placed in memory. The signals, with the flags, can then be used to produce a mass spectrum using the pulse count only signal, the analog only signal, or both.