910-269-EN, Rev. B, June 2011
Calibrating the EPOCH 1000 Series (Phased Array Mode) 277
17.2.2
Wedge Delay
The
Wedge Delay
calibration type allows you to properly correct for the delay
between the electronic firing of the transducer and the point in time when the sound
beam enters the test piece. This parameter is known as
CAL Zero
in the conventional
UT mode.
In phased array mode, this is a more complex parameter to evaluate than in the
conventional UT mode. In most phased array inspections, each focal law has a specific
wedge delay. This is because each focal law typically has a specific angle of inspection
with a different beam index point (BIP) on the wedge, and therefore, a different length
of wedge material to travel through before reaching the surface of the inspection
material. In phased array mode, the instrument calculates a wedge delay for each
focal law. When the currently selected focal law changes, the instrument dynamically
applies the corresponding wedge delay to the measurement readings.
The EPOCH 1000 Series allows you to use a single calibration step to calculate the
wedge delay for all focal laws. This allows accurate measurement readings of sound
path, depth, and/or surface distances for all angles of inspection through a single
calibration.
17.2.3
Sensitivity (Gain)
The
Sensitivity (Gain)
calibration type allows you to properly correct variations in
system sensitivity to a particular reflector across all focal laws. This calibration is
related to the fourth step of a conventional angle beam calibration, where the system
sensitivity is calibrated to a known reflector and the reference gain is established. The
sensitivity (gain) calibration essentially establishes a reference gain for every focal law
in the angular coverage area (sweep).
The instrument’s sensitivity to a particular reflector varies based on sound path and
wedge delay. Compared to low angles, high angles sound beam must travel a longer
material path to reach a given reflector. This increase in material path means an
increase in beam spread and beam attenuation, resulting in the reflector producing a
lower-amplitude indication on the screen.
The EPOCH 1000 Series allows you to use a single calibration step to track the
amplitude response of a single reflector across all focal laws within the angular
coverage area, and then apply individual gain adjustments for each focal law to
normalize the amplitude response of the given reflector.
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Summary of Contents for EPOCH 1000 Series
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