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”

Understanding Sensor Output Signals

Have you ever wondered why there are a multitude of sensor output signals that can be configured on pressure, temperature, humidity, or gas sensing instrumentation used in process or HVAC applications? Most of these offerings were originally setup to allow sensor manufacturers to better align with the inputs offered by manufacturers of programmable logic controllers (PLCs) and direct digital controllers (DDCs), which are used for controlling processes for both automation and HVAC control.

I’d like to focus on two of the most commonly used output signals and zero in on the advantages and/ or disadvantages these output signals offer. Two of the most commonly used output signals include analog current, typically 4 to 20mA, and analog voltage, typically 0-10V. Continue reading “Understanding Sensor Output Signals”