Filter soil detecting device

摘要

A filter soil detecting device includes a chamber provided in communication with an air channel at an air inflow side or outflow side of a filter provided in a pneumatic device. The chamber has a lens and a diaphragm to move toward or away from the lens by pneumatic pressure. The diaphragm has a mark on the surface opposite to the lens. The diaphragm moves toward or away from the lens by pressure variation at the air inflow side or outflow side of the filter, so that the image of the mark seen from the outside of the lens is varied to allow the determination of degree of soiling of the filter.