Olympus EPOCH 6LT, User Interface Manual

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DMTA-10084-01EN, Rev. 2, November 2018
Chapter 11 190
ultrasonic setup. The EPOCH 6LT also automatically adjusts measurement thresholds
and gain to allow immediate thickness measurements with minimal operator
intervention.
11.7.1 Key Features
Several key features included in the EPOCH 6LT corrosion module vary from
standard flaw detector operation.
• Automatic Do-Zero
Automatic do-zero corrects for internal electronic delays, cabling delays and
transducer delays to the end of the delay line. Automatic do-zero calculates the
zero offset of the system by measuring the time-of-flight of sound through the
end of the delay line material of the connected dual probe. The EPOCH 6LT uses
two pulsing channels to calculate the zero offset for each transducer element and
delay line. While this measurement does not correct for couplant variation or
surface conditions of the test piece, it calculates the majority of the zero offset
value required for accurate material measurements before you couple the
transducer to the test piece.
• Thickness Gage Measurement Algorithm
The corrosion module uses the measurement algorithm developed for the 38DL
Plus ultrasonic thickness gage. This measurement mode, unlike peak, edge, or
first peak mode, uses positive and negative minimum measurement thresholds to
make the measurement. In this way, the measurement is less affected by
variations in amplitude—a major source of inaccuracy in traditional flaw
detection corrosion applications. To ensure prominent echoes are correctly
measured, automatic gain control (AGC) is used to maintain dynamically
optimized amplification of the A-scan.
• Automatic Gain Control
Automatic gain control (AGC) enables the EPOCH 6LT to acquire consistent
measurements. AGC continuously optimizes the first detected echo to maintain a
consistent echo height and shape by adjusting the gain level of the system to a
predetermined screen height based on the selected probe.
• V-Path Correction
The EPOCH 6LT corrosion module includes V-path correction for all dual probes
in its standard probe library. Dual transducers are typically constructed with a
small angle of incidence in both the transmit and receive elements, known as the
“roof angle.” Because of the roof angle, sound is introduced to a test piece at a
small refracted angle. Therefore, the actual depth of a given reflector is slightly