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10 GAIN - ADJUSTING
The gain (the amplitude of the return echo) can be adjusted to suit a variety of applications. To
obtain valid readings the gain must be set to the correct level to give reliable return echoes:
•
Too much gain may result in erroneous measurements by detecting noise rather than the
material back wall itself.
•
Not enough gain may result in intermittent detection. It may also result in lack of detection on
internal flaws, pits, or porosity.
The gain setting on your gauge can be compared to the volume control of a home stereo system.
If you turn it up too much you cannot hear the music clearly. If it is turned down too much, you cannot
hear it at all.
Your gauge has three gain settings (LOW, MED, HIGH).
Note: When the echo-echo ThruPaint™ measurement mode is selected, the manual gain feature is
disabled and greyed out in the menu items. In this mode, your gauge switches to an automatic gain
mode (AGC) that optimises the gain setting automatically.
Your gauge has been optimised for the MED gain setting and for the majority of applications it can
be used at this setting. Some applications however may require the low or high gain settings:
10.1 Low setting
The low setting might be necessary for noisy or granular cast materials. If the reading becomes
sporadic and will not settle down or resolve on a thickness value, it is reasonable to assume that
the material is either very noisy aluminium, or granular cast iron. In this instance, reduce the gain
LOW to see if the reading settles down and becomes stable.
10.2 High setting
The high setting may be necessary when trying to measure a material that is hard to penetrate (due
to the material type, or the overall thickness of the material) and when locating fine pits or flaws. In
these instances, increase the gain to HI to see if the reading settles down and becomes stable.
10.3 To Select the gain Setting
1. Press
, scroll to the PROBE menu and then highlight the GAIN function.
2. Use the
and
3. Press
to return to the measurement screen.
Alternatively, adjust the GAIN function in the hot menu.
11 THRUPAINT™ MEASUREMENT TECHNIQUE
11.1 Introduction
The principle behind ThruPaint™ measurement is to measure the time between two backwall
echoes returning from the test material. Since both of these backwall echoes travel the same path
through the paint or coating, the thickness of the coating is subtracted out of the measurement so
17
arrows to select the gain setting required.
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