Correction Factors - Omega Engineering WTM-1000 User Manual

2
Operation
For Vane Type Anemometers:
1- Remove the chamber door. Open the clamp in the adjustable mounting block by
turning the wheel.
2- Place the vane propeller inside the chamber. Make sure it is in the center
of the chamber.
3- Place the vane window door.
4- Secure the vane propeller in place by tightening the clamp using the wheel.
5- Slide the Vane Clamp sleeve over the vane window door and up against the vane
probe to minimize any air leaks.
Once the air probe is in place (either Hot wire or Vane type), turn the air speed
selector switch from 2.5 m/s (492 FPM) up to 15 m/s (2953 FPM). Check the air
probe reading vs. the switch setting on the wind tunnel.

2.3 Correction Factors

For Hot Wire Anemometers:
If the environmental conditions are other than the standard conditions (70 ºF and
29.92 inches of Hg), you need to correct for them. Here is the correction factor
equation:
K1 = (29.92 / P) x (460 + T) / 530 where,
P is the Barometric pressure in inches of Hg
T is the ambient temperature in Degree F
There is a second correction factor which is a function of the air probe geometry (K2).
Table 1 lists K2 for different air probes. So, the actual air velocity is as follows:
Actual Value = Measured Value (Average value over one minute time) x K1 x K2
For Vane type anemometers:
You only need to correct for the air probe geometry (K2). The actual air velocity
is as follows:
Actual Value = Measured Value (Average value over one minute time) x K2
Model No. Description
FMA-904 Hot Wire 0-2000 FPM
FMA-905 Hot Wire 0-5000 FPM
HHF42 Hot Wire 40-3940 FPM
HHF801 Vane Type 160-2358 FPM
HHF802 Vane Type 80-4930 FPM
HHF803 Vane Type 160-4930 FPM
HHF91 Vane Type 125-4900 FPM
HHF92A Vane Type 80-6900 FPM
HHF81 Vane Type 80-5910 FPM
HHF82 Vane Type 80-5910 FPM
HHF11 Vane Type 80-6900 FPM
6
Correction Factor - K2
@ 2.5 m/s @5 m/s
1.04 1.00
1.00 1.00
1.04 1.00
1.08 1.12
0.90 0.96
0.94 1.00
0.86 0.92
0.92 0.97
1.03 1.06
1.14 1.18
0.88 0.90
@10 m/s @15 m/s
1.01 N/A
1.01 1.04
1.06 1.07
1.17 N/A
1.04 1.07
1.09 1.06
1.00 1.03
1.05 1.04
1.13 1.12
1.24 1.22
0.99 1.01