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”
Dwyer Instruments, Inc. is proud to announce the release of two new Multi-Jet Water Meter series. Continue reading “Dwyer Releases Two New Multi-Jet Water Meter Series”
Many Dwyer Instruments, Inc. products sense and measure pressure. This includes: gages, manometers, transmitters and switches.
Pressure is the amount of force acting on a specific area and is equal to the force divided by the area.
There are many types of pressure that are used and measured, including: atmospheric, absolute, gage, vacuum, differential and hydrostatic. Continue reading “What is Pressure and How is it Referenced?”
While summer is vacation time for most, it was the busiest time of year for the Dwyer marketing staff as we prepared for the launch of the 2018 Dwyer™ Catalog.
Many of your favorite products have been updated with new features, such as the addition of a High Accuracy version of our Magnehelic® Differential Pressure Gage; new lower ranges and an NPT process connection for our 616KD family of pressure transmitters; and new manifold valves for our Series 490A Hydronic Manometer. In addition to these updates, several new products have been released, including the Series AVUL Air Velocity Transmitter, that help make Dwyer a one-stop-shop for all of your instrumentation needs.
In order to help you select the proper products, the Dwyer team has added additional selection guides and product applications throughout the catalog. The selection guides help to compare products by differentiating the features and benefits. The application guides assist customers by mapping out items that are frequently purchased together for ease in ordering.
Be sure to request your FREE printed copy of the 2018 Dwyer™ Catalog today!
Dwyer Instruments, Inc. offers many flow measuring products including our very popular variable area flowmeters, often called rotameters. Dwyer manufactures variable area flowmeters in polycarbonate, the Series RM and LFM; in acrylic, the Series VF; and in glass, the Series VA and DR.
Variable area flowmeters have scales calibrated for specific media at specific conditions. Most commonly, the flowmeters are calibrated for air for gas use, and water for liquid use, at standard atmospheric conditions of 70 degrees Fahrenheit and 14.7 PSIA, which is 0 PSIG. When using the flowmeter in conditions other than these standards, the flow reading will not be accurate and corrections will need to be made.
Gases can have large differences in density based on pressure and temperature. The observed reading of the flowmeter is the actual flow rate. The flow rate corrected for pressure and temperature is the standard flow rate. Often for air use the pressure in the flowmeter is not atmospheric and a correction must be made to get the standard flow rate.
For correcting the flow rate to standard use the equation shown, where actual pressure P1, actual temperature T1, and actual flow rate Q1 are used.
When using the flowmeter for gas other than air, the specific gravity must be corrected for.
For this correction use the equation shown, where actual flow rate is Q1 and gas used in the flowmeter specific gravity is SG.
If manual corrections are not desired, Dwyer offers scales calibrated for other specific media; for example, nitrogen versus air. Dwyer can even create custom scales calibrated specifically for your application media, operating pressure, and temperature. Please contact our technical sales department for already existing scales or to have your own custom scale created.