The A20DP-K-15 Differential Pressure Swichgage is a 2" dual-scale dial, diaphragm-actuated differential pressure-indicating gage, with a built in electrical switch. This switch is used for tripping alarms and/or shutting down equipment. It also includes an adjustable ("K") knob, which allows you to make field adjustments without needing a 1/16" hex key. The A20DP-K-15, with a pressure range of 0-15 psi, is intended to monitor and indicate oil, fuel or water filter restriction and can reduce the risk of dangerously high pressure which may rupture the filter, resulting in contaminants entering the system. This filter restriction Swichgage will let you know when to change your filter and maintain peak efficiency. The gage mechanism is enclosed in a polycarbonate, break-resistant case and lens. A polished stainless steel bezel and O-ring seals help protect this rugged instrument from the external environment. Accuracy and protection from moderate overpressure is assured by a unique, unitized diaphragm chamber. A built-in pulsation dampener helps eliminate pointer flutter and is removable for cleaning. Inside the A20DP-K-15, the tempered nickel silver gage pointer acts as a pressure indicator and as one switch pole which completes a circuit when it touches the adjustable limit contact. Contacts have a self-cleaning motion to ensure electrical continuity. The A20DP-K-15 features a beryllium copper diaphragm sensing element and a 1/8-27 NPTM brass process connection. The adjustable limit contact is an SPST contact; pilot-duty only, 2A @ 30 VAC/DC; closed when the low limit is met, and open when the pointer is in normal operating range.