Adjusting The Extended Blank With Dual Element Transducers - Olympus 38DL PLUS User Manual

— Reduce the gain value when noise peaks are above 20 % of the waveform
display height.
This prevents the gage from detecting a noise peak rather than the correct
back-wall echo.
3. Press [GAIN] again to restore the last previously set gain.
4. Press [GAIN] again to return to the automatically adjusted echo height mode.
The default automatic gain mode is indicated by a blank Gain field.

10.2 Adjusting the Extended Blank with Dual Element Transducers

Olympus recommends using the extended blank parameter only when you are an
experienced operator who thoroughly understands the acoustic properties of the
material being measured. Incorrect use of the extended blank can cause the gage to
misread areas of thin material.
Normally, the 38DL PLUS searches for echoes down to nearly zero thickness.
However, some special circumstances such as a high degree of near surface corrosion,
aluminum material, enclosed flaws, or laminations can generate echoes that the
instrument may falsely detect as the low thickness. When these echoes are larger than
the sought after back-wall echo, the manual gain adjustment (see "Adjusting the Gain
with Dual Element and E110 EMAT Transducers" on page 135) cannot prevent this
false detection. However, the extended blank parameter allows you to define an early
period in which the 38DL PLUS will not perform echo detection, and therefore,
prevent erroneous measurements.
To use the extended blank
1. Press [WAVE ADJ].
The waveform adjustment parameter and its value appear on the measurement
screen (see Figure 10-2 on page 138).
2. If needed, use the [] and [] keys to select EXT BLANK.
The extended blank becomes active, but initially, its value is zero. The gage
remains in the measurement screen.
CAUTION
DMTA-10004-01EN, Rev. D, November 2016
Using Advanced Gaging Features 137