Checkline TI-CMXDL - Manual (Page 20)

Normal temperature range
Most standard transducers will operate from 0 ∞F to 180∞F.
High temperature measurements
Special transducers and couplants are available for temperatures above 180 ∞F up to 650∞F
with intermittent contact. It is necessary to cool the transducer, by submerging the trans-
ducer in water between readings, when measuring high temperatures.
Modes and temperature errors
In addition to errors caused by velocity changing with temperature, some modes
(measurement techniques) are affected more than others. For example, dual element mode
has larger errors due to changes in temperature of the delay line. However, in multi-echo
techniques, auto temperature helps to minimize these errors.
4.6 Measurement Modes
In this section we will discuss the different measurements modes the TI-CMXDL is
capable of operating in, the transducers required, and the reasons for using specific modes:
Pulse-Echo Mode (Flaw & Pit detection) – Coating Off (P-E)
Pulse-echo mode measures from the initial pulse (sometimes referred to as an artificial
zero) to the first echo (reflection). In this mode, either an automatic or manual zero can be
performed depending on the zero probe function setting. If the manual mode has been
selected, the transducer is placed on a reference disk, located on top of the TI-CMXDL,
and a key is pressed to establish a zero point for the particular transducer. If the Auto Zero
feature is enabled, a simple key press will perform an electronic zero to establish the same
zero point.
In this mode errors result from surface coatings and temperature variations.
Since pulse-echo only requires one reflection, it is the most sensitive mode for measuring
weak reflections (flaws) typically found when measuring heavily corroded metals.
V-Path Correction
Dual element delay line transducers have two piezoelectric elements
mounted at an angle on one end of the delay line. One element is used
for transmitting sound, while the other element only receives sound.
The two elements and their delay lines are packaged in a single housing
but acoustically isolated from each other with a sound barrier. This
allows the transducer the ability to achieve very high sensitivity for
detecting small defects. Also, the surface of the test material does not
have to be as flat in order to obtain good measurements.
Dual element transducers are normally used in pulse-echo mode for
finding defects, and in echo-echo mode for through coating measurements.
Dual element delay line transducers are usable over a range of 0.025 inches to 20 inches
depending on the material, frequency, and diameter.
A limitation of dual element delay-line transducers is the V shaped sound path. Because the
sound travels from one element to another, the time versus thickness relationship is non-
linear. Therefore, a correction table in the instruments software is used to compensate for
this error.
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Dual Element
Transducer
showing
V-path of signal
Important Note: For the duration of this chapter, all references to GRIDS and SEQ
LOGS should be considered synonymous with references to FILES.
11.2 Creating a new Grid or Sequential Log (File)
Important Note: This entire section is a step by step guide to successfully create a grid
sequential log. The instructions must be used in the sequential order specified, as follow
Creating a Name
Grid/Seq Log Name: Can contain a combination of up to 20 numeric, alpha, or special
characters listed in the first section of this chapter.
1. Press the MENU key once to activate the menu items tab. Press the MENU key multi
times to tab right, and the ESC key multiple times to tab left, until the DATA menu i
highlighted and displaying the submenu items.
2. Use the UP and DOWN arrow keys to scroll through the sub menu items until NEW
highlighted.
3. Press the LEFT & RIGHT arrow keys to toggle the data formats – GRIG LOG &
SEQ LOG.
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Sequential Log Formats
Grid Log Sequential Log