GE Everest XLG3 VideoProbe Operating Manual page 96

88 Chapter 7 Measuring Features and Defects
Types of Measurement
The XLG3 system supports four types of measurement: phase, stereo, shadow, and
comparison.
Measurement
Type
Phase
Stereo
Shadow
Comparison
Related Information
• "3D Phase Measurements"
• "Stereo Measurements"
• "Shadow Measurements"
• "Comparison Measurements"
Advantages
Over stereo, shadow or comparison
measurements:
• Optical tip is used for both viewing and
measurement.
• Automatic tip to target range-finding
indicator.
• Full screen view.
• More accurate depth measurements.
• Cross-section profile measurement.
• Increased measurement distances are
possible
• The surface need not be perpendicular to
the tip.
• Cross-section profile view
• 3D point cloud view
Over comparison measurements:
• More accurate.
• No known reference is needed.
• Can measure depth.
• The surface does not need to be
perpendicular to the probe view.
Over shadow measurements:
• The surface does not need to be
perpendicular to the probe view.
Over comparison measurements:
• More accurate.
• No known reference is needed.
• Can measure depth.
• Can measure distance along a skew
surface.
Over stereo measurements:
• Height and depth contours are more
discernible.
• You can measure along smooth, straight
lines.
Over shadow and stereo measurements:
• You can use the probe headguard only.
• You can measure with probe tip farther
away.
• You can measure large objects.
• You can check the approximate size of
many items quickly.
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GE Inspection Technologies XLG3 VideoProbe System
Disadvantages
The system cannot measure moving parts.
Highly reflective surfaces should be measured at an
angle.
The system may be unable to position the matching
cursors accurately with any of these conditions in the
measurement area:
• Insufficient detail
• Repeating patterns
• Glare
• Smooth, straight lines to measure along
In some cases, you can eliminate the problem by
repositioning the probe tip and adjusting the
brightness. Otherwise, try shadow measurement.
Measurement surface must be nearly perpendicular
to the probe view for an accurate measurement
(except for "skew" measurements).
The shadow is sometimes difficult to see.
You cannot always place the shadow where you
want it.
Less accurate than shadow or stereo
measurements.
Known references may not be present and may be
difficult to deliver to the measurement site.
Measurement surface must be nearly perpendicular
to the probe view for an accurate measurement.