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QDF70B Air Differential Pressure Transmitter
QDF70B is designed for micro differential-pressure measurement in dry-air systems, ventilation ducts and HVAC equipment. Small pressure changes across a filter, fan or airflow path can indicate operating condition, blockage or insufficient ventilation, but these changes are often too small for ordinary pressure transmitters. The dedicated low-pressure structure converts the air-pressure difference into a standard signal for the control system. This gives operators clearer airflow information, supports continuous duct monitoring and makes it easier to detect gradual changes before they develop into larger ventilation problems.
The H and L ports of QDF70B support differential, positive and negative pressure measurement. By connecting the high-pressure and low-pressure sides to the correct test points, the transmitter can compare two locations or reference one side to ambient pressure. This flexibility allows the same product type to be used for filter differential pressure, duct positive pressure or negative-pressure room monitoring. Clear H/L connections simplify tubing layout, reduce selection complexity and give technicians a practical way to adapt the installation to different air-pressure measurement tasks.
QDF70B uses barbed pressure ports that connect directly to flexible hoses. The hose can be pushed onto the port without adding separate threaded adapters, reducing the number of small fittings required at the installation point. This is particularly convenient in HVAC ducts, air lines and ventilation equipment where pressure taps are commonly linked by tubing. Direct hose connection shortens installation time, makes later disconnection easier and helps keep the pressure lines compact and organized during commissioning or maintenance.
Working Principle Diagram
