July 20, 2021 | Posted By: Degree Controls Inc.
The air velocity measured through a side-wall sensor is a function of the cabinet’s negative pressure, which is created by the airflow exhaust system. The negative pressure changes when a sash is opened, or the overhead exhaust system adjusts its speed, and this will manifest itself as a pressure change, which is measured by the side-wall sensor as a velocity change. The side-wall sensor’s measured velocity exhibits excellent correlation to these changes in pressure, and their corresponding effect on face velocity. In sidewall sensing for laboratory cabinets, the sidewall sensor acts as a flow-through velocity device, using room air, not contaminated exhaust air.