Anemometers will provide fast accurate air velocity readings in easy to access areas. When using the hold function or max/average features you will simulate wind turbulence problems that normally occur. For more restricted areas refer to hot wire anemometers.

Velocity and volume applications are sometimes very clean or very dirty. Hot wire anemometers are used in clean HVAC environments; where as static pressure tips are better suited for dirty and highly flammable environments. Both have higher m/s ranges and are suitable when access to ducts is limited to small openings.

Differential pressure and hot wire anemometers are the alternative measuring devices used when air contains particles, and only small openings are available to insert a probe.
 

The total flow rate of flow volume in cubic feet per minute (cfm) is easily computed using the formula:

To determine the average velocity, divide the opening into a number of equal areas. Take a velocity reading at the centre of each area and numerically average the results. If the velocity profile is relatively flat, only a few areas are needed. If the profile is not uniform, several equal areas should be used.

Generally, it is a good idea to make a rapid traverse across the duct in two dimensions to determine the uniformity of air velocity. If the velocity is not constant at one measuring point, use the mean velocity between the upper and lower readings.

With the newest microprocessor-based anemometers, up to a thousand data points can be stored in the meter's memory for mean velocity calculation. Some units can even multiply the mean velocity by the cross sectional area to give a readout in cfm. These capabilities provide tremendous new convenience for the HVAC professional.