Calibration of flow meters

[nagarajh]

I calibrate a venturi flow meter at non-standard conditions. I know the calibration is not good at a different location where the barometric pressure and temperature are different. How do I convert the displayed flow rate to actual flow rate? What is the best way around having to convert everytime I use the flow meter.

 

[CWIC]

Not sure if this is the right standard:
ASTM D 3195 "Rotameter Calibration".

 

[quark]

What are you measuring? It's not a problem with liquids(density variation is marginal), for a venturimeter calculates flow by taking pressure difference.

Regards,

 

[nagarajh]

I am measuring air flow rate. The flow rate is a function of the pressure difference and the density of air. Hence, I think we have to make the conversion everytime we use the flow meter in conditions other than what it was calibrated? Correct me if I am wrong. Thank you for your responses. I will also look up ASTM D 3195 "Rotameter Calibration"

 

[quark]

You are absolutely right with compressed air.

The link below explains you this in detail.

http://www.cleandryair.com/scfm_vs__icfm_vs__acfm.htm

You can use gas law to do density correction.

Regards,

 

[Heula]

Dear nagrajh
You must first get the venturi meter Head Vs Flow curve for different temp. Then only it will be possible for you to caliberate. Hence, this shall be obtained from the flow meter supplier only . Otherwise , no one can help it as the flow meter contant varies from supplier to supplier.
You must specify the medium , location etc. in which flow meter is placed.Then we can provide you specific solutions.

 

[jsummerfield]

As you have gained some insight, consider posting a more detailed question with all data in the Measurement and Control Instrumentation forum.

John