Converting CFM on an Anemometer help? 4.5 inch orifice on vacuum

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SUMMARY

The discussion focuses on converting airflow measurements to cubic feet per minute (CFM) using a CPS AVM 03 anemometer with a 4.5-inch orifice. The calculation involves determining the area of the orifice using the formula πr² divided by 144 to convert square inches to square feet. For example, with a velocity of 4 feet per second, the CFM can be calculated as 0.11 square feet multiplied by the velocity and then multiplied by 60. If the anemometer measures velocity in feet per minute, a simple division by 10 may suffice for CFM conversion.

PREREQUISITES
  • Understanding of basic geometry for area calculation
  • Familiarity with airflow measurement concepts
  • Knowledge of units conversion (square inches to square feet)
  • Experience with anemometers and their operation
NEXT STEPS
  • Research the CPS AVM 03 anemometer specifications and capabilities
  • Learn about airflow measurement techniques and best practices
  • Explore advanced airflow calculation methods for different orifice sizes
  • Investigate the impact of anemometer design on airflow accuracy
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This discussion is beneficial for HVAC technicians, engineers, and anyone involved in airflow measurement and analysis, particularly those using anemometers for precise airflow calculations.

Bonedrycarpet
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I have an anemometer that I bought that does not have the ability to put in the ID of the orifice I am trying to measure. In this case it is a 4.5 inch orifice-stays the same for me 95 percent of the time. Does anyone know how I convert the reading manually so that I can get an accurate reading on my anemometer?

Below is the link to the meter I bought on ebay-it is a cps avm 03.

http://rover.ebay.com/rover/0/e11051.m43.l1123/7?euid=88c820308fc348969bfbebe2f4e7378a&loc=http%3A%2F%2Fcgi.ebay.com%2Fws%2FeBayISAPI.dll%3FViewItem%26item%3D110905158318%26ssPageName%3DADME%3AX%3ARTQ%3AUS%3A1123

Thank you!:smile:
 
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I think you are asking how to calculate the volume per min given the diameter and velocity?

= area * velocity.

If you want it in cubic feet per min then the area needs to be in square feet and the velocity in feet per min.

The area is..

= ∏r2/144
= 3.14 * (4.5/2)2/144
= 0.11 square feet

So if the velocity is say 4 feet per second then the cfm is

= 0.11 * 4 * 60

If the anemometer reads in feet per min then you don't need to multiply by 60.

(Edit: I don't know how accurate you need the result but if the annemometer reads velocity in feet per min then it might be sufficient to just divide that by 10 and call it cfm)

All this assumes the anemometer doesn't block and reduce the airflow significantly.