SE-RDA User Instructions 100507-03 B
Copyright © 2021 The S.E.A. Group
27
Vertical offset correction
Before using and interpreting the data, the vertical (pressure or flow) offset must be
checked and, if necessary, corrected. This is ESSENTIAL because any offset will result in
significant errors in flow rates and volumes. Offset is usually caused by drift in the
pressure sensor.
Offset correction may be applied either automatically, using the “AutoOffs” button, or
manually.
To check if offset correction is required
1.
Move the selection cursors to select a range just before the onset of breathing
(yellow arrow, Figure A). The selection is displayed in the detail graph area (after
refreshing by toggling the Press/Flow switch). The selected period is at the end of
the “warm-up” period (indicated on the SE-RDA unit by a steady red LED).
2.
In the example, the steady trace at the left of the graph area sits slightly above
zero pressure. Toggle the Press/Flow switch to Flow (Figure B). The offset is now
much more marked: in the example, the trace sits at about +60 l/min.
3.
If there is a visible offset, correction is necessary.
A. Pressure
B. Flow
C. Flow corrected
Sequence showing vertical offset correction process
Automatic offset correction
1.
Select the Press/Flow toggle to Flow.
2.
Check that the 40 – 50 second period on the plot is a steady horizontal trace (it
should be if the unit was undisturbed during the warming up period).
3.
Click the “AutoOffs” button. An offset value will appear in the field “P Offs Corr,
mbar” above the button, and the horizontal trace should now be aligned with zero
flow. If this is not the case, the offset may be corrected manually.
Manual offset correction
The process is the same as automatic offset correction except that, instead of clicking
the “AutoOffs” button:
1.
Manually enter a value in the “P Offs Corr, mbar” field.
