Abstract: An example system includes an ion detector and a signal processing apparatus in communication with the ion detector. The ion detector is arranged to detect ions during operation of the system and to generate a signal pulse in response to the detection of an ion. The signal pulse has a peak amplitude related to at least one operational parameter of the system. The signal processing apparatus is configured to analyze signal pulses from the ion detector and determine information about the detected ions during operation of the system based on the signal pulses. The signal processing apparatus includes a discriminator circuit. The signal processing apparatus is programmed to vary a threshold of the discriminator circuit based on the at least one operational parameter of the system during operation of the system.