Dakota Ultrasonics CMX - Manual (Page 70)

66
CHAPTER NINE
PULSE-ECHO COATING & COATING TECHNIQUES
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 thickness 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 CMX has been designed to provide the user with the
ability to measure 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 CMX is preset to a coating velocity of 0.0850 in/µsec (2159 m/sec) from the
factory. This velocity is a very close approximation of the common coating velocities
found in the field. However, the 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 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 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 CMX
doesn’t recognize tha t a special coating enabled transducer is plugged into the
gauge, the coating feature will be disabled entirely. There are a number of coating
enabled transducers 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.