In today’s industry, the number of device output signals continues to grow. Each signal is different; so how do you figure out which one is right for your application? The easiest way to hone-in on the correct signals for your application is to decide whether you want a digital communication signal or an analog signal. Continue reading “Analog vs. Digital Device Signals”
It is the first day on the job for a new contractor. Their project is to balance the HVAC system of a commercial office space. The contractor measures the total pressure and static pressure in the office duct work, using an air velocity manometer, and then calculates the velocity. The velocity measurement seems high, so the contractor is led to believe that either the measuring instrument isn’t precise enough, or the calculations are off. Therefore, the contractor turns to a duct traverse to check the velocity measurement. Continue reading “Duct Traverse Process with Modern Technology”
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.
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”
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”
The velocity of an air stream in a duct is not uniform over the cross section of the duct. This is because friction against duct walls causes the air velocity to be lower near the sides than the velocity in the center, creating a parabolic velocity profile. Continue reading “Duct Traversing for Average Air Velocity and Air Volume”