Checkline TI-CMXDLP - Manual (Page 45)

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D. Baseline - The horizontal trace across the A-scan presentation for a no signal
condition. It represents time and is generally related to material distance or
thickness.
E. Gate – An electronic feature that allows the user to monitor signals inside the
boundaries of the gate settings. The height of the gate from the baseline is known as
the threshold, and controls the sensitivity of the relections that trigger a detection
from the opposite surface of the material.
F. Measurement Scale – Represents thickness values over a deined measurement
range, and labeled at the calibrated hash marks on the display (X) axis.
G. Digital Material Thickness Value – The thickness of the base material.
H. Minimum Thickness Value – Dynamically updates the value during a scan,and
displays the minimum thickness value found.
NOTE: Only visible when high speed scan mode is enabled.
I. Units – The current measurement units being used (English, Metric)
J. Velocity – The material velocity value the TI-CMXDLP is currently using or
calibrated for. Displayed in either English or Metric units, depending on what units
the gauge is set for.
K. RECT waveform – The half cycle, either positive or negative, of the RF sine wave,
created by the relected sound, or oscillation, from the material being measured.
This view is typically considered as “law” view.
L. Coating Thickness Value – Displays the actual thickness of any coating adhered
to a metallic material surface (PECT Mode), or a coating adhered to anon-metallic
surface (CT Mode).
M. Minimum Thickness Value – Dynamically updates the value during a scan,and
displays the minimum thickness value found.
NOTE: Only visible when high speed scan mode is enabled.
N. Feature Status Bar - Indicates the features currently enabled and in use in the
following order:·
• Measurement Mode (P-E, PECT, PETP, E-E, COAT)·
• Differential Mode (ON/OFF)·
• High Speed Scan Mode (ON/OFF)·
• Alarm Mode (ON/OFF/AUDIBLE)·
• Gain Setting (VLOW, LOW, MED, HI, VHI)
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8.0 Thru Paint Measurement Technique
8.1 Introduction to Thru Paint Measurement
The principle behind thru paint measurement is by measuring the time between
twobackwall echoes returning from the test material. Since both of these backwall
echoes travel the same path through the paint or coating, the thickness of the coating
is subtracted out of the measurement so that only the actual material thickness can be
measured. This feature saves the user a great deal of time scraping and removing the
coating from tanks and pipes during the inspection process.
The TI-CMXDLP also has a special echo-echo verify option, or triple echo mode.
This measurement mode is identical to the echo-echo mode described above, with an
additional third echo measurement performed to verify the measurement between the
irst 2 echoes. By doing this, the TI-CMXDLP can conirm that a peak jump has not
occurred, and the measurement made is stable and correct. This mode is only suitable
for thin materials and coatings, as the ability to achieve 3 relections is not always
possible.
The primary purpose of thru paint measurement is to determine actual or overall
material thickness by eliminating the coating thickness. Thru paint mode cannot be
used for law or pit detection. Therefore, inspectors may need to use echo-echo thru-
paint mode in conjunction with the standard pulse-echo law detection mode for some
applications. The combination applications. The combination of using both modes is
ideal for the advanced inspectors needs.
8.2 Using Thru Paint Mode
The irst thing to note in this section, is that by selecting the transducer type from the
list of probes stored in the TI-CMXDLP, a basic echo-echo thru paint coniguration
is recalled from memory. Each of the transducers in the list contains pre-conigured
echo-echo settings. However, ine adjustments may be necessary in order to be suitable
for your speciic applications. These conigurations are general setups only. Once the
transducer has been selected, or auto detected, and the appropriate calibration procedure
completed, the TI-CMXDLP can toggle between pulse-echo (law &pits), and echo-echo
(thru-paint) modes by simply pressing the MULTI MODE key located on the keypad.
The standard transducer that will be used for common steel applications is a ¼” 5MHz
high damped transducer (1/4IN – 5.0MHZ HD). However, any of the transducers with
the HD label have been optimized for echo -echo thrupaint applications. Any of the
auto recognition coating transducers are also highdamped transducers, and will work in
echo-echo mode as well.
NOTE: When a transducer is selected for use, all of the measurement modesavailable
for use with this transducer can easily be determined by pressing the multi mode button
on the keypad. The TI-CMXDLP has been programmed to identify the modes available
to a speciic transducer.