TSI DP-Calc micro manometer 5815 allows you to easily make HVAC pressure measurements. This robust instruments can be used with pitot probes to measure duct velocity. The DP-Calc 5815 is a simple to operate, hand held digital micro manometer for fast, accurate differential and static pressure measurements. Measure differential and static pressure from -15 to +15 in. H2O (-3735 to +3735 Pa). Calculate and display velocity when using a pitot tube. HVAC commissioning and troubleshooting. Testing and balancing. Pitot tube duct traverses. Static pressure measurements. Pressure drop across filters, coils, fans, and diffusers. Environmental air flow testing. DP-Calc micro manometer includes instrument, hard carrying case, 4 alkaline batteries, operation and service manual, calibration certificate. Measures 3.3-inches width by 7-inches height by 1.8-inches thick.