A hub unit adapted for use in a monitoring system that monitors engine performance parameters of a gas turbine engine. The hub unit includes a housing, at least one signal conditioning circuit board within the housing and adapted to receive the analog sensor outputs from the sensors, and a control circuit board within the housing, connected to the signal conditioning circuit board, and adapted to produce digital data corresponding to analog sensor outputs. The control circuit board and the signal conditioning circuit board each comprise electrical circuit components that define an analog signal processing path and have accuracy and precision characteristics that drift in response to component aging and to changes in the temperature to which the hub unit is subjected. The hub unit performs a continuous calibration scheme to determine and remove errors in the analog signal processing path resulting from the drifts of the electrical circuit components.