Velocity Measurement and Environmental Effects

Differential pressure measurement can be beneficial in a wide variety of building automation system (BAS) applications.

One of these applications involves determining if a filter in your system needs to be cleaned or replaced. Filter health can be established by monitoring the pressure on the primary and secondary sides of a filter. A clean filter will typically have a baseline differential pressure generated as air flows through it. As the filter becomes dirty, this differential pressure increases.

When using a mechanical flow sensor, such as a pitot tube, differential pressure can also be used to determine flow velocity and volumetric flow. Continue reading “Velocity Measurement and Environmental Effects”

Air Velocity and Flow Measurement with Pitot Tubes

Pitot Tubes Series 160, 166T, and 160S

Dwyer offers many styles of Pitot tubes. Pitot tubes are commonly used sensors for monitoring air velocity and flow rate in heating, ventilation, and air conditioning. Some examples include the: Stainless Steel Pitot Tube Series 160, Telescoping Stainless Steel Pitot Tube Series 166T, and “S” Type Stainless Steel Pitot Tube Series 160S.

Henri Pitot

Pitot tubes are based on Bernoulli’s equation, which states that an increase in the speed of a fluid occurs simultaneously with an increase in dynamic pressure and a decrease in static pressure. Pitot tubes sense the dynamic pressure of the fluid flow at a particular point and were invented by French Engineer Henri Pitot in the early 18th century. Continue reading “Air Velocity and Flow Measurement with Pitot Tubes”

Understanding Air Velocity Sensors

Stainless Steel Pitot Tube, Series 160

Dwyer Instruments, Inc. offers a multitude of sensors for monitoring air velocity in HVAC systems. Some of this instrumentation has a simple construction (Pitot tubes, for example) while others are more complex, such as hot-wire anemometers.

The initial term and first “hot-wire anemometer” was developed back in 1914 by Louie Vesso King. He is also accredited for King’s Law, which mathematically describes heat transfer in air flows using a heated wire. As the air moves over the wire, it causes a loss of temperature in the wire and removes some of the wire’s heat energy. Continue reading “Understanding Air Velocity Sensors”