Static pressure is typically measured using a manometer, or sometimes a differential pressure sensor connected to static pressure taps.
Here's a breakdown:
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Manometer: A manometer is a U-shaped tube filled with a liquid (often water or mercury). One side of the tube is connected to the point where you want to measure static pressure, while the other side is open to the atmosphere (or connected to a second pressure point for differential measurement). The difference in liquid levels between the two sides indicates the static pressure relative to atmospheric pressure (or the pressure difference between the two points). For HVAC systems, this often involves drilling small holes (static pressure taps) into the supply and return ducts.
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Differential Pressure Sensor: A differential pressure sensor is an electronic device that measures the difference in pressure between two points. Similar to using a manometer in an HVAC system, you would use static pressure taps on the supply and return ducts of an HVAC system, connecting each tap to a port on the differential pressure sensor. The sensor converts the pressure difference into an electrical signal, which can be displayed on a screen or used for control purposes.
Here's a step-by-step example for measuring static pressure in an HVAC system using a manometer:
- Prepare the Manometer: Ensure the manometer is properly calibrated and filled with the correct fluid.
- Create Static Pressure Taps: Drill small holes into the supply and return ducts of the HVAC system. These holes should be perpendicular to the airflow to minimize the influence of dynamic pressure.
- Connect the Manometer: Connect the manometer tubing to the static pressure taps. Typically, one side of the manometer is connected to the supply duct, and the other side to the return duct.
- Take the Reading: Observe the difference in fluid levels in the manometer. This difference represents the static pressure difference between the supply and return ducts. In many HVAC applications, total static pressure is calculated by adding the absolute values of the supply and return measurements.
For example, if the manometer shows a positive pressure of +0.5 inches of water column (in. w.c.) on the supply side and a negative pressure of -0.3 in. w.c. on the return side, the total static pressure would be 0.5 + 0.3 = 0.8 in. w.c.
