Dakota Ultrasonics DFX-8 plus MANUAL1 - Manual (Page 37)

DFX-8 Series Ultrasonic Flaw Detectors
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2) Use the UP and DOWN arrow keys on the left button wheel to scroll
through the sub menu items until GAIN is highlighted.
3) Press the LEFT and RIGHT arrow keys on the right button wheel to
scroll the value. When the correct Gain is displayed, proceed to step 8.
4) Alternatively, press the ENTER key to display the Digits Edit Box.
5) Press the LEFT and RIGHT arrow keys multiple times using the left
button wheel to scroll the highlighted value.
6) Press the UP and DOWN arrow keys multiple times on the left button
wheel to scroll the digit locations.
7) Repeat steps 5 & 6 until the Gain value is correctly displayed.
8) Press the OK key to set the Gain and return to the menu screen, or ESC to
cancel entering the Gain.
9) Finally, press the MEAS key to return to the measurement screen.
4.4 Gates
The gates are an important part of any ultrasonic device, in this case a flaw detector.
The primary purpose of using a flaw detector is to “detect” and estimate the “size” of
of flaws according to calibrated reference standards or simulated defects. The gates
play an important role in this process, as without them a detection/measurement isn’t
possible. The height of a gate is also a threshold, or controls the level of sensitivity.
They can be adjusted to a specific reference height, based a predetermined reflector,
and set to act as an alarm during the inspection process.
The more flexible a gate is, the better the possibilities for the user to setup an
application. For example, a test block with a target size and depth is optimized on
the A-Scan display with a signal amplitude at 70% full screen height. The inspector
wants to know of any defects during the inspection that are greater than or equal in
size to the calibrated test specimen. A gate is then enabled and set to a reference
height of 70%. The width and range are adjusted to cover the range tested, and the
inspection is underway.
The DFX-8 is equipped with 2 fully independent gates. Each gate has a start and
stop or width, a threshold, a polarity switch, and a detect option. A gate can only