BSA Flow Software Installation and User's Guide - CSI

Traverse coordinates of a datum point
Figure 5-35 The traverse range and the laboratory coordinate system, (only
two coordinates shown for clarity)
The traverse axes are assumed parallel with the laboratory coordinates, but
they may have opposite sign conventions on one or more axes. This is dealt
with by the Direction property as explained under the traverse properties.
Initially, the software only knows the traverse coordinate system. Therefore,
some known position in the laboratory coordinate system, a datum point,
must be used to relate the laboratory coordinates to the traverse coordinates.
The datum point must be within the traverse range, and it must be possible to
accurately position the LDA measuring volume at this point.
If the datum point is the laboratory origin, initialisation is simply done by
moving the LDA measuring volume to the datum point, and resetting the
traverse coordinates by clicking the Reset button in the Traverse Dialog.
However, in practise the datum point may be different from the laboratory
origin. The software therefore operates with two properties: Reference
position and Offset position.
Reference position is the laboratory origin’s coordinates in the traverse
coordinate system. It can be outside or within the traverse range.
Offset position is the datum point’s coordinates in the traverse coordinate
system. It must be within the traverse range.
Both of these must be known to initialise the traverse coordinates. If they
coincide it suffices to input the traverse coordinates of the position in the
Reference position value field.
The laboratory coordinate system usually refers to symmetry planes or
boundaries of a flow rig, e.g. center line, wall, center of turntable, or to a
well defined part of an object around which the flow is investigated, e.g. the
corner of an object, the center of a circular, cylindrical or spherical object,
etc.
To establish the traverse coordinates of a datum point , use the Traverse
Dialog (right-click on the traverse icon in the BSA Application):
1. Move the traverse to its home position, click Reset if the position
display does not show (0,0,0)
2. Move the traverse to the datum point using the X, Y and Z position fields
and up/down arrows. See below for recommended methods to determine
whether the measuring volume is in position.
3. When the measuring volume is at the datum point, read the current
traverse position from the Traverse Dialog position display, and type
these coordinates into the Offset position in mm field of the traverse
properties (one traverse axis at a time).
4. Knowing the Offset position’s laboratory coordinates, the Reference
position in mm’s traverse coordinates can be calculated. Type these into
the Reference position in mm field of the traverse properties.
5. Click Reset. The position display should now display the laboratory
coordinates of the datum point, and the initialisation procedure is
complete.
BSA Flow Software: Project explorer objects 5-41