TSI Incorporated Alnor LoFlo Balometer Mode D'emploi page 14

Correction Factors for Standard Flow Rate to Actual Flow Rate
The LoFlo Balometer measures standard volumetric
flow rate. Standard flow is defined as the flow rate at
standard conditions, 70°F (21.1°C) and 14.7 psia
(29.92 inHg, 760 mmHg). Actual flow rate is the true
volumetric rate of air at the local temperature and
barometric pressure. If you desire standard flow rate,
use the displayed reading. However, if the actual flow
rate is desired, use the information below.
To correct the standard flow rate to actual flow rate use
the equation below.
V act = V std x CF
V act = Actual flow rate
V std = Standard flow rate (this is displayed by
the instrument)
T act = Actual Temperature
ρ act = Actual barometric pressure
ρ std = Standard density 0.075 lb/ft
(at 70°F and 14.7 psia)
ρ a
= Actual density in lb/ft
12
APPENDIX A
3
3
CF = ρ
/ρ (Correction Factor)
std a
Using the equations or chart below, you can bypass the
full density calculation.
Calculations in imperial units
CF = (14.7/ ρ act )*(460+ T act )/530
Where ρ act is in psia and T act is in °F
Calculations in imperial units
CF = (29.92/ ρ act )*(460+ T act )/530
Where ρ act is in inHg and T act is in °F
Calculations in metric units
CF = (760/ ρ act )*(273.15+ T act )/294.25
Where ρ act is in mmHg and T act is in °C
For your convenience, we have made a chart for
determining the correction factor given temperature and
pressure.
! NOTE: The atmospheric pressure as reported by
the National Weather Service is corrected to sea
level and cannot be used if measurements are not at
sea level.