Dakota Ultrasonics UMX-2 - Manual (Page 43)

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CHAPTER TEN
PULSE-ECHO COATING & COATING TECHNIQUES
10.1 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 UMX-2 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 UMX-2 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, this can be changed to another known coating velocity,
using DakView3 utility software to set a ‘custom’ velocity that can be uploaded to the
UMX-2.
10.2 Enabling Pulse-Echo Coating Mode (PECT)
The special PECT mode is only available for use with ‘dual element’ transducers.
When the UMX-2 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
UMX-2 doesn’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 transducers available from Dakota. Please contact us with your
application requirements for additional information on frequencies and diameters
currently offered.
Note: When PECT mode is used, the coating value cannot be viewed on the UMX-2.
Only the base material thickness is displayed. However, if the measurements are
stored to a file and downloaded to a PC, the coating measurements can be viewed
as they are saved within the file. The actual A-Scan waveform is also stored in the
file. This can prove very valuable, as it provides the inspector additional confidence
that the measurement was successful overall. Finally, all UMX-2 settings are also