Olympus 38DL PLUS, User Manual

Page: 148 / 318

DMTA-10004-01EN, Rev. D, November 2016
Chapter 10 136
Figure 10 ‑ 1 Manually adjusting the gain
When activated, the manual gain adjustment also modifies the way in which echoes
are shown on the waveform display. With the default automatic gain, the measured
echo peak is visible on the display so that you can readily observe the measured echo
position, independently of its strength or of the gain. When you manually adjust the
gain, the displayed echo height changes to be proportional to the actual echo
amplitude at the receiver output, allowing you to readily observe gain changes.
The peak detection threshold for thickness calculation is at 20 % of the waveform
display height, the first graticule line above the baseline in Figure 10-1 on page 136.
The peak amplitude of measured echoes must be at or above the threshold to be
processed for thickness calculation.
To view, restore, or change the gain value
1. Press [GAIN] to view the current automatic gain value.
The gain value appears near the lower-right corner of the display. The waveform
display changes to the amplitude proportional to gain mode.
2. Press [

] or [

] to adjust the gain in steps of ±1 dB.
The gain value and the height of the echoes change accordingly.
— Increase the gain value when the peak amplitude of the echo that should be
detected is below 20 % of the waveform display height.
This prevents the gage from reading a too high value when skipping one
back-wall echo, measuring twice the correct thickness (doubling).
Echo detection
threshold at 20 % of
waveform display
height
Manually adjusted gain
value