The 0 to ± 20 In. H²O Integral Sensor with built in Silicon Diaphragm and 1/8 inch NPT male fitting includes: Pure silicon diaphragm sensor built into the unit. A linear output signal suitable for computer, PLC, or security systems. Operates on a 9 VDC battery. Momentary display switch for reading of approx. 100 seconds or can be switched to continuous display.