Checkline TI-44N - Manual (Page 10)

6.2 Setup Of Gauge When Acoustic Velocity Is Unknown
In applications where the type of material is not known or the material type
is not listed in the Acoustic Velocity Selection Table the following steps can
be performed to set the gauge to measure accurately.
1. Measure a sample of the material using a micrometer, caliper or similar
measuring device.
2. Turn the power on by pressing the POW key.
3. Place a small amount of couplant fluid on the sample and place the probe
on the sample.
4. After a thickness value is shown on the LCD display along with the Good
Coupling Indicator, remove the probe from the sample.
5. Use the ▲ and ▼ keys to increase or decrease the displayed value until
it equals the known thickness of the sample as measured in Step 1. When
the
▲ key is pressed the “UP” indicator will be show on the LCD display.
The “LOW” indicator will be shown for the ▼ key.
6. The acoustic velocity setting will be automatically adjusted to the correct
value for this material after Step 5 is completed.
7 . Change modes to either Mode C or Mode A to display the current acoustic
velocity, as described in section 6.4. Write this value down so it can be
re-entered without having to repeat the above procedures should you need
to change the acoustic velocity to another setting.
6.3 Changing Acoustic Velocity Settings
After determining the required acoustic velocity for the material to be
measured, the acoustic velocity must be adjusted by using either of the
following methods:
• Selecting one of the ten (10) preset values [Mode C, Coarse Adjustment]
• Adjusting the velocity to the desired setting [Mode A, Fine Adjusment]
METHODS FOR CHANGING ACOUSTIC VELOCITY SETTINGS
MODE Select one from Use ▲ or ▼ Last Setting ➔1900 ➔2700 ➔
C a list of 10 keys to index ➔ 4170 ➔ 4700 ➔ 5570 ➔ 5790
Preset Values thru selections ➔ 5930 ➔ 6260 ➔7390 ➔10000
MODE Fine Adjustment Use ▲ or ▼ Any acoustic value can be set
A to desired value keys to increase from 1000 to 12000 m/sec
or decrease value
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6.4 Thickness Measurement Methods
(a) Standard mode vs. aluminum mode
The instrument is shipped with the standard sensitivity settings suitable
mainly for steel measurement. In addition to this, it provides an aluminum
measurement mode with lower sensitivity (approx. 10 dB less than the
standard mode).
High-sensitivity equipment will often pick up too much noise when
measuring materials with small ultrasonic attenuation (e.g. aluminum),
resulting in erroneous thickness values.
(b) S to B 1 method
Thickness (D) is determined using the
time difference between the upper surface
reflection (S-echo) and the first bottom
surface reflection (B-echo). This method
is mainly used for steel measurement.
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