A method and associated product for wear level determination. The axis direction seal member and the side seal member make contact with one another such that there is no gap between the axis direction seal member and the side seal member in a rotation axis direction of the developing roller. The temperature difference between the saltwater and the water running through the water coil create a temperature gradient causing salt-free water to distill from the saltwater. When the external force disappears, the second stopping portion slides toward the first stopping portion by a resilient force of the elastic member until the first stopping portion and the second stopping portion are engaged. The secondary circuit may have less complex harmonics, but may generate values only within the desired range.