When doing a blower door test, do you ever use long term average? Why or why not?
Digital pressure and flow gauges have an option for time averaging, such as 1, 5 or 10 seconds, long term or a manual time average option.
Under what circumstances would you use the long term average and why?
When the wind is breezy, I use long term averaging. The more the pressure jumps around due to breezes, the longer the term that I use. Even then, I mentally average the readings. This is after I have taken steps to shield the end of the outside hose from the wind.
Wind is probably the most frequent reason for using the time averaging with our manometers, but there is another that we need to be careful with. Manometers are unique in that they ignore barometric pressures. Place your refer tube out the front door and walk your manometer (long tube) upstairs or into the basement and even though the top to bottom pressure may vary (on a cold day) by 50 pascals or more our manometers will register very little. When the temperature of our tubes and the air inside is the same as in the house, any changes in elevation are canceled out. However, if those tubes just came out of an ice cold vehicle, or a hot one, and have not fully acclimated, our readings will drift. In this case, before we start averaging we need to allow those tubes to become room temperature. The section of tube that goes outside needs to acclimate as well.
I never use any setting but "long term" average. Any other setting will always give you a less accurate average reading. Under the "long term" setting the manometer automatically calculates a mathematically continuous average. That means that you can "hold " the reading after "any" length of time and it will give the average for all of the seconds that you had the meter running.