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23 MEASUREMENT - OPTIONS
Further
information
www.elcometerndt.com.
The Polarity function is used in the same way for the flaw detector as it is for the thickness gauge.
Polarity is selectable depending on the VIEW, GT1, GT2 and DAC settings
23.1 DETECT MODE
Your gauge has three detection modes; Z-Cross, Flank, and Peak. The following diagrams illustrate
the difference between the options:
Z-Cross
In the diagrams, the current polarity is positive (as shown by the position of the gate - above the
baseline).
Z-C
: The detection occurs as the first positive half cycle crosses the baseline and goes
ROSS
negative.
F
: The detection occurs as the first half cycle left edge rises and breaks the threshold.
LANK
P
: The detection occurs at the highest peak in the gate.
EAK
To adjust the Detect Mode setting:
1. MENU/TUNE/DETECT MODE
2. Use LEFT and RIGHT to adjust the value of DETECT MODE.
3. Press MEAS to return to the measurement screen, ready to begin taking readings.
23.2 PULSE WIDTH
See "Pulse Width" on page 24.
23.3 PULSER VOLTAGE
Your gauge has a 200 V square wave pulser that can be adjusted for specific applications and
transducers. The standard pulser setting is 150 V, and the Pulser Volt function allows you to
increase or decrease this value by 50 V to give greater penetration for difficult material types, or
increased resolution on noisy materials.
To adjust the Pulser Voltage setting:
See "Pulser Voltage" on page 25.
23.4 PULSE REPETITION FREQUENCY (PRF)
Your gauge has an adjustable pulse repetition rate (8 Hz, 16 Hz, 32 Hz, 66 Hz, 125 Hz, 250 Hz and
333 Hz). This setting determines how fast the pulser fires. The repetition rate is tied into the alarm
LEDS. Therefore, when scanning at higher speeds, a higher repetition rate will make the alarm
trigger more responsive. It is important to note that since the screen has a maximum refresh rate of
120Hz, any PRF settings over this maximum will not be visible on the display (in fact, the human
eye has a response rate of less than 60 Hz).
can
be
found
on
the
Elcometer
NDT
Flank
Knowledge
Centre
Peak
on
44
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