Model AFS-303 is a general purpose proving switch with gold contacts suitable for HVAC, Energy Management and DDC (Direct Digital Control) applications. It can be used to sense positive, negative, or differential air pressure. The plated housing contains a diaphragm, a calibration spring and a snap-acting SPDT switch. The AFS-303 has a field adjustable set point range of 0.05″ wc to 12.0″ wc. . It is equipped with three ¼”, 90º, quick-connect spade terminals. Two compression ferrule and nut sample line connectors accept ¼” OD rigid tubing.