If more convenient,
approximate correction factors may be determined using the
following formulas.
A. Pressure:
where
Q1 = Observed flowmeter reading
Q2 = Actual flow corrected for pressure
P1 = Standard atmospheric pressure, 14.7 PSI
P2 = Actual pressure, 14.7 PSI + pressure in PSI inside
flowmeter. Measured at outlet on all but TMV units, Inlet
pressure on TMV models.
B. Specific Gravity:
where
Q1 = Observed flowmeter reading
Q2 = Actual flow corrected for specific gravity
1 = Specific gravity of air
S.G. = Specific gravity of gas being used in flow meter
originally calibrated for air.
NOTE:
The corrections shown in the curves and in the formulas
are for variations in specific gravity and internal pressure*
only. Further correction may be necessary for variations
in viscosity and changes in type of flow from laminar to
turbulent or vice versa. This is particularly true in the
case of extremely low flows of the lighter gases. Nevertheless
these charts and correction factors can be quite useful
when dealing with small changes in pressure* and specific
gravity.
*Measured at discharge on all but TMV
units. Inlet pressure on TMV models.
