GE Mentor Visual iQ Manual Del Usuario página 106

Measurement Plane EVA Warnings Measurement Plane EVA Warnings


When using a Measurement Plane with Point to Line, Area, or
When using a Measurement Plane with Point to Line, Area, or
Depth to measure near an edge, the viewing perspective can
Depth to measure near an edge, the viewing perspective can
affect accuracy, especially if the edge has a significant radius.
affect accuracy, especially if the edge has a significant radius.
To help the user maximize accuracy, the system displays an
To help the user maximize accuracy, the system displays an
Edge View Angle (EVA) value next to the MTD and an Edge Edge View Angle (EVA) value next to the MTD and an Edge
View Angle Line (EVA Line) in the point cloud views. The ideal
View Angle Line (EVA Line) in the point cloud views. The ideal
EVA of 0° occurs when the EVA Line is perpendicular to the
EVA of 0° occurs when the EVA Line is perpendicular to the
Measurement Plane. Measurement error generally increases Measurement Plane. Measurement error generally increases
as the EVA increases when measuring near a rounded edge. as the EVA increases when measuring near a rounded edge.
If the EVA exceeds an upper limit (25° for Point to Line, 35° If the EVA exceeds an upper limit (25° for Point to Line, 35°
for Area and Depth) with cursors placed near an edge, the
for Area and Depth) with cursors placed near an edge, the
system displays a warning message, flashes an orange outline system displays a warning message, flashes an orange outline
around the MTD and EVA, and shows the EVA Line in orange. around the MTD and EVA, and shows the EVA Line in orange.
To reduce the EVA, inspect the Full Image point cloud, in which
To reduce the EVA, inspect the Full Image point cloud, in which
the four dotted 3D Perspective Lines show the corners of the
the four dotted 3D Perspective Lines show the corners of the
field of view, and visualize how the relative positions of the
field of view, and visualize how the relative positions of the
tip and the object must be adjusted to make the EVA Line
tip and the object must be adjusted to make the EVA Line
more perpendicular to the Measurement Plane, shown as a
more perpendicular to the Measurement Plane, shown as a
solid blue rectangle. Capture a new image with the adjusted
solid blue rectangle. Capture a new image with the adjusted
positions, and repeat the measurement.
positions, and repeat the measurement.
14
106

Some points regarding the Edge View Angle (EVA):
Some points regarding the Edge View Angle (EVA):
• It is the angle between the Measurement Plane and an It is the angle between the Measurement Plane and an
•
Edge View Plane determined using two 3D coordinates on Edge View Plane determined using two 3D coordinates on
the edge and the origin of the field of view where the four
the edge and the origin of the field of view where the four
dotted 3D Perspective lines in the Full Image point cloud dotted 3D Perspective lines in the Full Image point cloud
converge. To help visualize this concept , open the front
converge. To help visualize this concept, open the front
cover of a hardcover book and hold the edge of the cover
cover of a hardcover book and hold the edge of the cover
up close to your eye. The cover represents the Edge View
up close to your eye. The cover represents the Edge View
Plane, the first page represents the Measurement Plane, the
Plane, the first page represents the Measurement Plane, the
joint between them represents the edge of the surface, and
joint between them represents the edge of the surface, and
the angle between them represents the EVA.
the angle between them represents the EVA.
Moving cursors along a straight edge has little impact on
• • Moving cursors along a straight edge has little impact on
the EVA because the Edge View Plane does not change.
the EVA because the Edge View Plane does not change.
The EVA depends on the position of the edge in the image.
• • The EVA depends on the position of the edge in the image.
The top left image shows a poor EVA when measuring near
The top left image shows a poor EVA when measuring near
the left side of the image with a perpendicular view at the
the left side of the image with a perpendicular view at the
center. The right image shows a much better perspective at
center. The right image shows a much better perspective at
the part edge, which is reflected in the low EVA. the part edge, which is reflected in the low EVA.
Rotating a side-view tip in a fixed position (e.g., borescope
• Rotating a side-view tip in a fixed position (e.g., borescope •
port) has little impact on the EVA. Movement of the viewed port) has little impact on the EVA. Movement of the viewed
object or translation of the tip is generally needed. object or translation of the tip is generally needed.
As shown in the lower left image, achieving a low EVA does
• As shown in the lower left image, achieving a low EVA does
•
not require a perpendicular view of the part . In the book
not require a perpendicular view of the part. In the book
analogy, you can tilt and move the book while maintaining a analogy, you can tilt and move the book while maintaining a
90° angle between the cover and the first page. 90° angle between the cover and the first page.
If the edge along which the measurement is performed has
• If the edge along which the measurement is performed has
•
a small edge radius relative to the measured dimension,
a small edge radius relative to the measured dimension,
accurate results can be achieved even with an EVA warning
accurate results can be achieved even with an EVA warning
present when the edge is coming toward the probe tip. present when the edge is coming toward the probe tip.
Avoid measuring with high EVA values on edges going away Avoid measuring with high EVA values on edges going away
from the tip.
from the tip.
See the "Measurement Plane Guide Lines" section for
• See the "Measurement Plane Guide Lines" section for •
measuring on rounded edges with high EVA values.
measuring on rounded edges with high EVA values.
Measurement Plane Guide Lines Measurement Plane Guide Lines
Guide Lines are shown in the point cloud views when using a Guide Lines are shown in the point cloud views when using a
Measurement Plane with Length, Point to Line, Multi Segment,
Measurement Plane with Length, Point to Line, Multi Segment,
or Area. They are shown as black lines that are perpendicular or Area. They are shown as black lines that are perpendicular
to the Measurement Plane and extend from the cursor to the Measurement Plane and extend from the cursor
locations on the Measurement Plane to surface points straight locations on the Measurement Plane to surface points straight
above or below the cursor locations. Spheres are shown
above or below the cursor locations. Spheres are shown
where Guide Lines intersect the surface. where Guide Lines intersect the surface.
Example Applications:
Example Applications:
Edge damage on rounded turbine blade or vane edges
•
• Edge damage on rounded turbine blade or vane edges
Turbine vane platform to shroud gaps
•
• Turbine vane platform to shroud gaps
Edge radius estimates
•
• Edge radius estimates
Gap width
• Gap width •
Any in-plane dimensions between points not on the same
• • Any in-plane dimensions between points not on the same
plane
plane
Conventional Measurement on a Diagonal
Conventional Measurement on a Diagonal
Best Practices to Improve Measurement Accuracy:
Best Practices to Improve Measurement Accuracy:
Adjust the cursor positions in the 2D image until the Guide
• • Adjust the cursor positions in the 2D image until the Guide
Lines and surface spheres appear on the surface in the
Lines and surface spheres appear on the surface in the
desired locations.
desired locations.
Use when measuring on rounded edges and an in-
•
• Use when measuring on rounded edges and an
plane measurement like that obtained using an optical
in-plane measurement like that obtained using an optical
comparator is desired. The conventional Point to Line
comparator is desired. The conventional Point to Line
measurement of a rounded leading edge indication in
measurement of a rounded leading edge indication in
the lower left image is on a diagonal and therefore gives
the lower left image is on a diagonal and therefore gives
a larger result than would be obtained using an optical
a larger result than would be obtained using an optical
comparator. The same indication is measured in the top
comparator. The same indication is measured in the top
left image using a Measurement Plane with Guide Lines to
left image using a Measurement Plane with Guide Lines to
remove the angle.
remove the angle.
Cannot be reliably used if the EVA is more than about 10°
• Cannot be reliably used if the EVA is more than about 10° •
and the rounded edge is away from the probe tip. and the rounded edge is away from the probe tip.
Cannot be used when the 3D data does not extend all the
• Cannot be used when the 3D data does not extend all the •
way to the edge of the surface.
way to the edge of the surface.
• Should be used to guide cursor positioning on rounded Should be used to guide cursor positioning on rounded
•
edges oriented toward the probe tip, especially when
edges oriented toward the probe tip, especially when
the EVA exceeds about 15°. The rounded edge is off the
the EVA exceeds about 15°. The rounded edge is off the
measurement plane, so unless the EVA is low, the cursors measurement plane, so unless the EVA is low, the cursors
cannot be placed properly using only the 2D image. This cannot be placed properly using only the 2D image. This
is especially true with higher EVA values that generate is especially true with higher EVA values that generate
warnings as shown in the above two images.
warnings as shown in the above two images.
VideoProbe 3D Measurement Handbook
VideoProbe 3D Measurement Handbook | 15
05/2018