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”
Many Dwyer Instruments, Inc. switch products have standard snap-action switches. Snap-action switches have a mechanical movement that snaps the contacts together and apart to make or break an electrical circuit.
Silver contact snap switches are very versatile and offer high contact ratings commonly up to 10 or 15 amps when used with 120 volts AC. These switches are often used for control circuits with heavier load requirements such as pumps, motors, fans, and incandescent light bulbs. Continue reading “Use of Gold Contact Snap-Action Switches”
The primary goal of HVAC technology is to determine the most effective approach to heat/cool the interior of commercial sized buildings. One of the most effective ways of achieving this goal is through the use of chilled beam systems. Continue reading “Chilled Beam Systems”
Vane or paddle flow switches are used to initiate high or low flow alarms. A common application is as a low flow alarm for shut-down of a system for protection of the components from damage. Often these are used in cooling lines, oil lines, or monitoring other fluid flows that are critical for the system to operate. Continue reading “Custom Vanes for the V4 Vane Operated Flow Switch”
Dwyer Instruments, Inc. offers a wide variety of temperature sensors that use RTDs as the sensing element.
RTDs are based on the principal that the electrical resistance of the wire is a function of the temperature, with the resistance increasing as temperature increases. The resistance varies nearly linearly with temperature per the Callendar Van-Dusen equation. The wire used in RTDs as the sensing element is usually constructed of platinum, copper, or nickel. Platinum is the best material for this element, as it has the widest useful temperature range of these materials. It also has a very repeatable and linear temperature to resistance correlation. Continue reading “RTD Temperature Sensors”