The invention relates to a device for measuring and processing an input signal (To) of at least two decades, comprising: an electron multiplier (4) that has an exponential gain on the basis of the power supply voltage (Vm) thereof and which receives said input signal (To); a power supply (5) that provides the power supply voltage (Vm) of said multiplier (4); a control circuit (6) of the power supply (5), the gain (10) and shift (11) parameters of which are adjustable and define an output signal range while varying the exponential gain of said multiplier (4); a logarithmic compression amplifier (T), the output of which is received as an input of the control circuit (6) so as to vary the exponential gain of the electron multiplier (4), in a continuous manner over the dynamic range of a measurement, on the basis of the output signal (IoG) of the electron multiplier (4), and forming the output signal (Vout) of said device; a measuring and calculating means for predetermining the value of the exponent (b) for the exponential gain of the electron multiplier (4) and for calculating the gain (10) and shift (11) parameter values of said control circuit (6) on the basis of the value of said predetermined exponent (b). The invention also relates to a corresponding leak detector and measuring and processing method.