Correct pressure switch operation is integral to the safety of a furnace environment. The Fieldpiece SDMN6 is a dual-port manometer that also accurately tests pressure switches by simulating a draft with an internal pump. The Fieldpiece SDMN6 allows you to test pressure switches the right way. Adjust the pump s speed to create a negative pressure (vacuum). The red LED indicates when the switch closes. View the closing and opening pressures directly on the LCD. The Fieldpiece SDMN6 dual-port manometer measures ±60 inches of water column high enough for gas manifold pressures. Check building pressurization with a static pressure resolution of 0.01 WC. View P1-P2 in the bottom line of the display to check the performance of a blower.