Checkline TI-25M - Manual (Page 12)

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5 .0 QU I CK START I N ST RU CT I ON S — ST EEL T H I CK N ESS
These Quick Start procedures are intended for those applications where the thick-
ness of steel is to be measured. If a material other than steel will be measured,
the gauge must be calibrated for use on this particular material. Refer to Sections
6.0 through 8.0 for additional details.
Quick Start Instructions
1. Turn on the power by pressing the key.
2. Plug the probe cable into the receptacle at the top of the gauge.
3. Place a drop of coupling fluid on the built-in Probe Zero Plate.
4. Grasp the probe and place it on top of the Probe Zero Plate.
Apply moderate pressure to the top surface of the probe with
your index finger or thumb to stabilize the probe and to keep
the wearface seated flat against the measurement surface.
5. The display will show some thickness value and the Stability Indicator
will have most of its bars illuminated.
6. While keeping the probe on the Probe Zero Plate, press the key.
The display will show a value that can be recorded for future use.
7. Remove the probe from the Probe Zero Plate. The gauge is now ready to
perform thickness readings on steel samples.
8. Place a small amount of coupling fluid on the steel surface to be
measured and proceed as explained in step #4 above.
9. The gauge will display the thickness of the steel wall along with the
Stability Indicator showing the relative stability of the reading. If fewer
than five (5) bars are illuminated, the thickness reading displayed is most
likely inaccurate.
Notes
a. When the probe is removed from the sample after a measurement, the
last reading will be retained on the display.
b. Occasionally, a small film of couplant will be drawn out between the
probe and the surface as the probe is removed. When this happens, the
TI-25M may perform a measurement that is larger or smaller than it
should be. This phenomenon is obvious when one thickness value is
observed while the probe is in contact with the material, and another
value after the probe is removed.
c. The gauge will automatically power off after 5 minutes of non-use.
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6 .0 CALI BRAT I ON FOR M EASU RI N G T H I CK N ESS OF
M AT ERI ALS OT H ER T H AN ST EEL
Ultrasonic Thickness Gauges use sound waves to measure wall thickness.
Different types of materials have different inherent acoustic velocities. For
instance, the acoustic velocity of steel is 0.2330 IN/µs (inches-per-microsecond),
versus that of aluminum, which is about 0.2500 IN/µs. It is critical that the
TI-25M be set for the correct acoustic velocity depending upon the material to be
measured.
The TI-25M is shipped from the factory calibrated for steel with an acoustic
velocity of 0.2330 IN/µs (5920 M/s). To measure the thickness of any other mate-
rial, the calibration will have to be changed by adjusting the acoustic
velocity to the appropriate value for the specific material being measured.
When checking the thickness of the built-in Test Plate, the gauge should display
the “Equivalent Value” (inches or mm) listed in the Acoustic Velocity Table in
section 6.1.
To determine the proper acoustic velocity for the non-steel material, refer to the
Acoustic Velocity Table, section 6.1. After determining the proper acoustic
velocity, the gauge must be re-calibrated for this new value as described in
section 6.2 Changing Calibration - Acoustic Velocity Is Known.
If you do not know the type of material to be measured or if the material type is
not listed in the Acoustic Velocity Table, refer to section 6.3, Changing
Calibration - Acoustic Velocity Is Not Known.