Retrotec Residential Pressure & Air Leakage - Manual (Page 11)

Page 11 of 75
1.7 Reduce uncertainty in results by taking lots of readings
Table 1 shows tests with approximate uncertainties that can result from applying various number of Baseline
points, Baseline times, and Time Averaging when taking induced pressures. As the number of Baseline points,
the Baseline time, and Time Averaging used for induced pressure readings increase, the uncertainties decrease.
For example, repeating the test using the same fan reduces the uncertainty by 5% in each case. Typical
uncertainties would be less than half of the values shown, however the table exaggerates the uncertainty trend
assuming there are errors while testing with different fans, gauges, and test conditions.
Table 1: Test result uncertainties vary by changing the number of baseline points, the baseline time, and Time Averaging for induced
pressures.
Gauge
error
Fan
error
Baseline
points
Baseline
time
Baseline
variation
Time Averaging for
induced pressure
Uncertainty
1%
5% 1 5 s 1.5 Pa 5 s 22%
1%
5% 30 5 s 1.5 Pa 10 s 8.6%
1%
5% 30 10 s 1.5 Pa 10 s 7.9%
1%
5% 30 10 s 1.5 Pa 100 s 6.5%
1%
5% 30 20 s 0.5 Pa 100 s 5.9%