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Airflow Sensor Differential Pressure Transmitter Airflow Signal Conditioner Card
Amplified Differential Pressure Across Flow Diamond
Flow Exhaust Meter Details
Special Solutions
Problem: Fume Hood Not equipped with flow metering device
Solution: Simple fume hood exhaust flow meter
Product Parts Description
Air flows over the airflow-sensing device, and a differential pressure signal is produced. With no air flow, this differential pressure signal is zero. The diameter of the tube and the flow obstruction with the air flow sensor is sized to produce a differential pressure of about 1.0 W.C. when the velocity in the tube is approximately 2900 fpm. The cross-sectional area through the tube (pd2/4 = area) times this maximum velocity determines the size of the box needed for each application.
A common 1.0 W.C differential pressure transducer is normally used on all devices, and the diameter of the tube is varied to match maximum flow for the application required by each device.
The signal from the differential pressure transducer produces a 10 vdc signal when the differential pressure transducer sees a 1.0 W.C. drop across the flow sensor. This signal varies in a non-linear way as the velocity and the induced differential pressure signal across the flow sensor are reduced. This relationship is a second order or square root relationship. Thus, an airflow signal conditioner essentially produces a 0 - 10 vdc output signal linear with net flow and producing with input of a 0 10 vdc input signal from the differential pressure device.
