Abstract: A sensor device (8, 15, 20) for monitoring the volume of granular food or candy contained in a pick-and-mix container (2), wherein the sensor device (8, 15, 20) comprises at least one pair of electrodes (10, 11), a capacitance meter (12) and a controller (13). The capacitance meter (12) is connected to the at least one pair (9, 16) of electrodes (10, 11, 17, 18) and operable to measure the capacitance over the at least one pair (9, 16) of electrodes (10, 11, 17, 18) to produce an output indicative of the capacitance through the container (2).