Abstract: A smart shaft position encoder apparatus is described which can be used for measuring changes in liquid levels. The apparatus employs dedicated logic and decoder circuitry for converting the raw shaft sensor data into instrumentation-compatible format. The raw shaft sensor data is generated by a shaft pulse generator which provides a pulse for each discrete change in shaft position. The sequence of pulses indicates whether shaft rotation is in a clockwise or counterclockwise direction. A preferred shaft pulse generator includes three reed switches which are operated by four permanent magnets mounted on a support disk which rotates in accordance with the position of the shaft, such shaft being coupled to a float pulley when used as a liquid level recorder. A rotation position detector is coupled to the shaft interface and produces output pulses in response to the raw shaft position data from the shaft interface.