What is the best instrument for measuring airflow from a supply air grill or diffuser?

The best instrument for measuring airflow from a supply air grill or diffuser is the hood type instrument. This device is specifically designed to capture and measure the total volume of air flowing out of a supply duct or diffuser. It works by using an air-collecting hood that covers the grill, allowing the airflow to enter the hood where it can be measured accurately.

Hood type instruments are particularly effective in applications where airflow measurement is crucial for maintaining proper ventilation and air distribution in HVAC systems. They provide an average airflow measurement across the entire area of the diffuser or grill, which is especially important in situations where flow can be uneven due to design or installation characteristics.

In contrast, while a vane anemometer can measure airflow, it typically measures point velocities, which may not provide an accurate representation of the total airflow from a grill or diffuser. A digital flow meter is generally more suited for ducted applications with straight runs and is not optimized for supply air grills. A thermocouple, on the other hand, is used primarily for measuring temperature, not airflow.

Therefore, the hood type instrument is most appropriate for this application because of its design and functionality in accurately measuring airflow from diffusers and grills in heating, ventilation, and air conditioning settings.