Olympus EPOCH 6LT, User Interface Manual

Page: 103 / 232

DMTA-10084-01EN, Rev. 2, November 2018
Calibration 93
thin material thickness allows for zero offset calibration, and the thick material
thickness allows for velocity calibration.
• Echo-to-echo
This calibration mode allows you to use any echo-to-echo measurement to
calibrate for material velocity only. In echo-to-echo calibration, the effects that
cause zero offset are eliminated by gating a particular indication that represents
the start point of the measurement. A second gate is set to track that gated
indication to acquire a measurement.This means that you must only calibrate for
the material velocity of the sample to acquire accurate echo-to-echo
measurements. You can perform echo-to-echo measurements between gate 2 and
gate 1 (
G2–G1 ), and this calibration mode will only be available if gate 2 tracking
is turned on (see “Gate Tracking and Echo-to-Echo Measurements” on page 79).
8.2.2 Angle Beam Modes
Angle beam calibrations can be performed using one of two modes:
• Sound path
This standard angle beam calibration mode uses the sound path measurement of
two different known material thicknesses to properly calibrate the instrument.
Typically, these sound path measurements are made from the radius of a
calibration test block. The smaller (thin) sound path measurement allows for zero
offset calibration, and the larger (thick) sound path measurement allows for
velocity calibration.
• Depth
This angle beam calibration mode uses the known depth of two different
reflectors to properly calibrate the instrument. Typically, these depth
measurements are made from side-drilled holes of equal size. For accurate
measurements, you must first verify the refracted angle of the transducer, since
the EPOCH 6LT calculates depth values based on sound path and known
refracted angle. The shallow reflector depth allows for zero offset calibration, and
the deep reflector depth allows for velocity calibration.
8.3 Calibration Procedure
The calibration described in this section is for a straight beam thickness calibration.
The calibration requires a test block with two known thicknesses, made from the
material to be measured. Ideally, the two thicknesses should represent thicknesses