Checkline TI-CMX - Manual (Page 20)

5.0 S ELECTING THE M EASUREMENT M ODE
5.1 The setup library
The TI-CMX contains 64 user configurable preset locations to store custom setups for
easy recall. These setups can be optimized for the user’s specific application needs and
can also be stored on a PC and transferred bi-directionally using Dakota’s PC interface
software included with the instrument.
5.2 Which mode & transducer do I use for my application?
High penetration plastics and castings
The most common mode for these types of applications is pulse-echo. The TI-CMX has
been optimized for cast materials. Cast iron applications require 1 - 5MHz frequencies,
and cast aluminum requires a 10MHz frequency. Plastics typically require lower fre-
quencies depending on the thickness and make-up of the material. Larger diameters offer
greater penetration power because of the crystal size, for difficult to measure materials.
Corrosion & Pit Detection in steel and cast materials
Use pulse-echo mode whenever attempting to locate pits and flaws. Typically a 5MHz
transducer, or higher, will be used for these types of applications. Use low frequencies
for greater penetration and use higher frequencies for better resolution.
Measuring Material & Coatings
The pulse-echo coating mode should be used when both material and coating thickness
are required, while still requiring the ability to detect flaws and pits. A special coating
style transducer is required for use in this mode. There are a variety of coating transduc-
ers in various frequencies available from Electromatic.
Thru Paint & Coatings
Often times, users will be faced with applications where the material will be coated with
paint or some other type of epoxy material. Since the velocity of the coating is approxi-
mately 2.5 times slower than that of steel, pulse-echo mode will induce error if the coat-
ing or paint is not completely removed. By using echo-echo mode, the user is able to
successfully measure through both, the coating and steel, and completely eliminate the
thickness of the paint or coating. Therefore, the steel can be measured without having to
remove the coating prior to measuring. Users will often use pulse-echo mode and echo-
echo mode in conjunction when performing inspections on coated materials.
Thru coating measurements require special high damped transducers. The most common
transducers are the 3.5, 5, and 7.5MHz hi damped transducers. These transducers are
suitable for use in both pulse-echo and echo-echo modes. This conveniently enables the
user to accurately measure overall material thickness using the thru Coating mode, and
then conveniently switch to pit detection mode without changing transducers. The _”
5MHz Hi damped transducer is the most commonly used transducer for standard thru
coating applications.
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9.0 P ULSE -E CHO C OATING & C OATING T ECHNIQUES
9.1 Introduction to Pulse-Echo Coating Measurement (PECT)
In the previous sections we’ve discussed the need for detecting pits and flaws (pulse-
echo) in materials, along with the requirement to measure through and eliminate errors
caused by coated materials (echo-echo). Until now, both modes were needed in order
accomplish both tasks. Pulse-echo mode was used for flaw detection, and echo-echo
mode was used to eliminate the coating thickness and provide a nominal material thick-
ness only. With this in mind, it often became cumbersome toggling between both modes
respectively.
In a majority of applications involving coated materials, inspectors are often interested
in monitoring both the thickness of the material, as well as the thickness of the coating.
Therefore, the TI-CMX has been designed to provide the user with the ability to meas-
ure the material and coating thicknesses simultaneously, while maintaining the ability
to detect flaws and pits all in a single mode called Pulse-Echo Coating (PECT). This
is accomplished by using a custom hybrid combination mode utilizing properties
from the basic modes along with a group of special techniques and theoretical wave
phenomena’s.
The TI-CMX is preset to a coating velocity of 0.0850 in/µsec (2159 m/sec) from the fac-
tory. This velocity is a very close approximation of the common coating velocities found
in the field. However, the TI-CMX also has a built-in one and two point calibration
options to calibrate to coating samples with a known thicknesses.
There are two coating modes built into the TI-CMX:
1. Pulse-Echo Coating (PECT) – used during inspections where both the material
and coating thicknesses are required.
2. Coating Only (CT) – used during inspections where only the coating thickness is
required.
9.2 Enabling Pulse-Echo Coating Mode (PECT) & Coating (CT)
When the TI-CMX is initially powered up, the gauge will automatically check to see if
the transducer plugged into the gauge can be recognized. All Dakota Ultrasonics coating
enabled transducers are equipped with the auto recognition feature. If the TI-CMX does-
n’t recognize that a special coating enabled transducer is plugged into the gauge, the
coating feature will be disabled entirely. There are a number of coating enabled trans-
ducers available from Dakota. Please contact us with your application requirements for
additional information on frequencies and diameters currently offered.
The coating modes can be enabled in three different ways:
1. On Power up and probe recognition.
2. By pressing MULTI MODE keypad.
3. From the tabbed menus under TUNE, MEASURE MODE.
The steps that follow will demonstrate all three methods in the order listed above.
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