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©Retrotec Inc. 2012

The @ Pressure function provides unique advantages over un-extrapolated results:

 There's no need to achieve an exact test pressure.

 The results on the screen will be very stable since results are extrapolated to a specific pressure.

 Results can be obtained, even if the test pressure cannot be reached.

In Set Speed mode

1. Press [@ Pressure] to view the results at a particular pressure, as set in the Setup Menu.

The units will change to indicate that @ Pressure is on (e.g. [email protected]).

2. Press [@ Pressure] again to view the current (non-extrapolated) results. The units will

change to indicate that @ Pressure is off (e.g. CFM).

In Set Pressure mode

1. Press [@ Pressure] once to view the results at the current Set Pressure value. The units will

change to indicate that @ Pressure is on (e.g. [email protected]).

2. Press [@ Pressure] again to view the results at the @ Pressure, as set in the Setup Menu.

The @ Pressure value will change (e.g. [email protected]).

3. Press [@ Pressure] again to view the current (non-extrapolated) results. The units will

change to indicate that @ Pressure is off (e.g. CFM).

It is important to understand how to use this feature properly, as inaccurate results are likely if it is

used incorrectly. The extrapolation feature works by estimating a typical leakage constant, and using it

to calculate the results at the desired pressure. In general, if the desired test pressure is within +/- 10%

of the actual measured pressure, the @ Pressure will be accurate enough to record. This function

should only be turned on and made active when in the appropriate situation – do not leave it on for all

tests as this may lead to inaccuracies. See below for examples.

Example #1 - Inaccuracy

A 50 Pa building pressure is desired, but only 20 Pa can be reached (due to severe leakiness). In this

instance, the extrapolated results for flow '@ 50 Pa' do not represent the reality of the testing

conditions and might be highly inaccurate.

In the same situation, a 45 Pa building pressure is achieved. The extrapolated '@ 50 Pa' pressure is now

much more accurate, and provides an acceptable result.

Example #2 - Set Speed

With the fan set at 100% speed, a building pressure of 46 Pa is reached. The gauge is setup to calculate

flow in CFM, and the @ Pressure setting is @50 Pa.

Press [@ Pressure] once. Each time the key is pressed, the results alternate between displaying “CFM”

and “CFM @50Pa”.

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Retrotec DM-2A Manual de usuario Pagina 22