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position, etc.).
The so-called DGS diagram forms the basis for this com-
parison of the reflecting power. This diagram consists of a
set of curves showing the connection of three influencing
variables:
•
Distance D between the probe and circular disk-
shaped equivalent reflector
•
Difference in gain G between various large circular
disk-shaped equivalent reflectors and an infinitely
large backwall
•
Size S of the circular disk-shaped equivalent re-
flector. The influencing variable S always remains
constant for one curve of the set of curves
The advantage of the DGS method lies in the fact that you
can carry out reproducible evaluations of small discon-
tinuities. The reproducibility is most of all important, for
example, whenever you aim to carry out an acceptance
test.
Apart from the influencing variables already mentioned,
there are other factors determining the curve shape:
•
sound attenuation
•
transfer losses
•
amplitude correction value
•
probe
The following probe parameters affect the curve shape:
•
element or crystal diameter
•
frequency
•
delay length
•
delay velocity
You can adjust these parameters on the instrument in
such a way that you can use the DGS method with many
different probes and on different materials.
When the DGS function is in use, echoes from equally
sized reflectors located at varying depths appear to lie
along the DGS Reference Curve. When operating in
DGS mode, the DGS Reference Curve appears on the
display screen. Before using the DGS function, do the
following:
•
Calibrate the instrument/probe combination
•
Make all required instrument settings related to the
pulser, receiver, and material-velocity settings.
The instrument will prevent changes to certain settings
after the DGS Reference Echo has been recorded and
PHASOR XS Operating Manual
5. Making Conventional Measurements
DGS is turned ON.
5.14.1 Specifying a Probe and Preparing
to Record the Reference Echo
Before using the DGS feature to evaluate reflectors in test
pieces, the characteristics of the attached probe must be
specified, certain characteristics of the reference standard
must be input, and a reference echo must be stored. To
specify the probe characteristics:
Step 1: Press
below the DGS Menu on the HOME
menu bar.
Step 2: Select the SETUP Submenu, then the PROBE
# function. Once activated, this function allows you to
choose from the list of probe types in
are probes for which probe characteristics are already
input in the instrument, with the exception of the user-
defined probe (PROBE # 0):
Step 3: If the user-defined probe type (PROBE #0) is
selected, you can then select the PROBE NAME func-
tion. Then use the Gain and Function knobs (the Gain
knob changes location within the name, the Function
knob changes the character value) to input a new name.
Note that selecting any PROBE # value other than 0 will
DGS PROBE-NUMBER ASSIGNMENTS
Instrument
Probe
Setting
Type
PROBE #0
User defined PROBE #17
PROBE #1
B1S
PROBE #2
B2S
PROBE #3
B4S
PROBE #4
MB2S
PROBE #5
MB4S
PROBE #6
MB5S
PROBE #7
MWB45-2
PROBE #8
MWB60-2
PROBE #9
MWB70-2
PROBE #10
MWB45-4
PROBE #11
MWB60-4
PROBE #12
MWB70-4
PROBE #13
SWB45-2
PROBE #14
SWB60-2
PROBE #15
SWB70-2
PROBE #16
SWB45-5
Table
5-1. These
Table 5-1
Instrument
Probe
Setting
Type
SWB60-5
PROBE #18
SWB70-6
PROBE #19
WB45-1
PROBE #20
WB60-1
PROBE #21
WB70-1
PROBE #22
WB45-2
PROBE #23
WB60-2
PROBE #24
WB70-2
PROBE #25
MSEB-2
PROBE #26
MSEB-4
PROBE #27
MSEB-4
(roof angle)
PROBE #28
MSEB-5
PROBE #29
SEB-1
PROBE #30
SEB-2 KF5
PROBE #31
SEB-4 KF8
PROBE #32
SEB-2
PROBE #33
SEB-4
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