TE-5170DV TSP VFC 22 Operations Manual
Po/Pa = 1 - Pf/Pa
where: Pa = ambient barometric pressure during calibration, mm Hg.
Using Po/Pa and the ambient temperature during the calibration, consult the Look Up Table to find the
actual flow rate. Record these flows in the column titled Look Up.
Calculate the percent difference between the calibrator flow rates and the sampler flow rates using the
following equation:
% Diff. = (Look Up Flow - Qa)/Qa * 100
where: Look Up Flow = Flow found in Look Up Table, m3/min
Qa = orifice flow during calibration, m3/min.
The EPA guidelines state that the percent difference should be within + or - 3 or 4%. If they are greater
than this a leak may have been present during calibration and the sampler should be recalibrated.
Example Calculations
The following example problems use data from the attached VFC sampler calibration worksheet.
After all the sampling site information, calibrator information, and meteorological information have
been recorded on the worksheet, actual air flows need to be determined from the orifice manometer
readings taken during the calibration using the following equation:
1. Qa = 1/m[Sqrt((H2O)(Ta/Pa))-b]
2. Qa = actual flow rate as indicated by the calibrator orifice, m3/min
3. H2O = orifice manometer reading during calibration, in. H2O
4. Ta = ambient temperature during calibration, K ( K = 273 + oC)
5. Pa = ambient barometric pressure during calibration, mm Hg
6. m = slope of Q actual orifice calibration relationship
7. b = intercept of Q actual orifice calibration relationship.
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