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GATE — adjusting the height of the gate.Only when the waveform is higher
than the gate, the gauge can take the echo and show the value. Attention: this
will only show when the GATE specification is highlighted. The first
intersection point between the waveform and gate is pointed by a red arrow,
which can help judging whether the thickness value is correct (the red arrow
should point the front of the first bottom echo if correctly tested).
3.11 waveform of the 0.02in sheet by PT04
3.5 Real Cases Analysis of A-Scan
1. When measuring the thickness, it's possible that that over small gains
prevent the precise results. As showed in the following figure, the thickness of
the testing object is about 5mm, but as for the very small gain, the measuring
result is 10.77mm as the first echo has not broken the gate and the gate locates
the second echo automatically. This is obviously an incorrect result, and
customer can pull up the echo by enhancing the gain setting to make the first
echo brake through the gate to achieve the correct measurement.
3.12 REAL CASE 1
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2. There are some defects in the testing object, and the gate locks the defect
echoes. As showed in the following figure, the thickness of the testing object
is about 10mm, but as there are obvious defects (the defect echoes are showed
on the display) and the gate locks the defect echoes which have broken the
gate, thus, the testing result shown is the thickness of the defect area. The right
measurement can be realized by adjusting the gate setting above the defect
echoes.
3.13 REAL CASE 2
3. If there are some surface faults in the testing object and the gate locks the
defect echoes, the measuring result will be the thickness of the defect area. In
this condition, the customer can use the BLANK function to get the correct
testing result. As showed in the following figure, the line on the bottom of the
screen, which we use to shield the defect echoes, indicates the blank confines
and makes the gate not catch the echoes within the blank confines, thus, the
right thickness value is acquired.
3.14 REAL CASE 3
18
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