Question: What setpoint should I set my differential pressure switch to for indicating when my filter is dirty?
Ask the Expert – Filter Status Switch
Control Valve Trim Styles and Flow Characteristics
Hi-Flow™ Control Valves vary the flow in a system by throttling the valve plug in and out of the valve seat. The corresponding flow rate through the valve is based on the valve plug and seat type, which is part of the valve trim. Dwyer Instruments, Inc. offers several flow characteristics, needle plugs, and restricted trim options for the Hi-Flow™ Control Valve series.
There are two types of inherent flow characteristic trim styles available in the Hi-Flow™ product line: Linear and Equal percentage. Continue reading “Control Valve Trim Styles and Flow Characteristics”
Ask the Expert – Issues with Referencing Outside Air Pressure
Question: I am trying to measure building pressure relative to outside air pressure. However, in doing so, I am seeing fluctuations in the differential pressure readings. Is there any way to minimize or eliminate these fluctuations? Continue reading “Ask the Expert – Issues with Referencing Outside Air Pressure”
What are Thermo-Anemometers or Hot Wire Air Velocity Sensors?
Dwyer Instruments, Inc. offers many air velocity measuring products that use thermal or hot-wire sensors as the sensing element. There are fixed duct mount styles for continuous monitoring, such as the Air Velocity Transmitters, Series 641, and portable insertion styles for testing, such as the Thermo-Anemometer Test Instrument, Model 471B and the Thermo-Anemometer Probe, Series AP2.
Continue reading “What are Thermo-Anemometers or Hot Wire Air Velocity Sensors?”
Flow Measurement with Orifice Plates
Dwyer Instruments, Inc. offers many types of flow measuring products including orifice plates, which are used as a flow sensing element with a differential pressure monitor.
Orifice plates are a primary flow element, detecting the flow of a fluid passing through the plate by sensing the pressure drop across the plate. When a fluid flows through a restriction in a pipe, it creates a pressure difference between upstream and downstream of the restriction. This pressure difference is proportional to flow rate according to Bernoulli’s principal, similar to a Pitot tube. Orifice plates are commonly used as they are simple to use, low cost, work with gases or liquids, and require low maintenance. Adversely, they do have large pressure losses with about 50% of the pressure drop not recoverable. Continue reading “Flow Measurement with Orifice Plates”