Abstract: A printer includes a container, a detecting unit and a management unit. The container is used for accommodating an imaging material, where the imaging material is a liquid material or a powdery material. The detecting unit is disposed on a surface of the container. The management unit is coupled to the detecting unit. The detecting unit detects a capacitance value to determine a remaining capacity of the container. When the remaining capacity is higher or lower than a threshold, the detecting unit transmits a trigger signal to the management unit. When the management unit receives the trigger signal, the management unit generates a notification.