The Johnson Controls DP140005U21D Differential Pressure Transmitter is a low-pressure sensing device designed to measure pressure differences in HVAC and building automation systems. It monitors pressure across air filters, ducts, fans, and other components, converting the measured differential pressure into a 4–20 mA signal for system controllers. With a 0 to 5 in. W.C. unidirectiona... https://www.partshnc.com/dp140005u21d-johnson-controls-pressure-transmitter-0-5-wc-4-20ma-0-5