Checkline TI-25DL - Manual (Page 15)

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6.0 CALIBRATION FOR MEASURING THICKNESS OF
MATERIALS OTHER THAN STEEL
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-microsec-
ond), versus that of aluminum, which is about 0.2500 IN/µs. It is critical that
the TI-25DL be set for the correct acoustic velocity depending upon the
material to be measured.
The TI-25DL is shipped from the factory calibrated for Common Steel with
an acoustic velocity of 0.2330 IN/µs (5920 M/s). To measure the thickness
of any other material, the calibration will have to be changed by adjusting
the acoustic velocity to the appropriate value for the specific material being
measured.
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.
Note: When possible, it is advised to calibrate the gauge using the 2-Point
Calibration Method described in Section 6.4.
8.0 ALARM & BEEPER MODE
The TI-25DL incorporates a powerful Alarm mode that provides the user
with audible and visual cues whether the measured value is above (GO) or
below (NO-GO) a user set nominal (alarm limit) value. The Beeper mode is
used in conjunction with the Alarm mode to provide an audible warning
(“beep”) when the measured value falls below the nominal value.
When the Alarm mode is set to “On” and a nominal value (alarm limit) is
entered, the “green” LED located above the MODE key will be illuminated.
If a measured value falls below the nominal value, the green LED will turn
off and the red LED will turn on. A series of “beeps” will also be heard
(assuming the Beeper mode is turned on).
The Alarm and Beeper modes can also be used together with the Scan
mode. While the probe is being scrubbed (dragged) along the measuring
surface, the audible and visual alarms will immediately activate if the gauge
encounters any readings during the scan that are below the user set nominal
value. Refer to Scan mode, Section 7.0 for additional details.
The following procedures outline the steps necessary to set the Alarm &
Beeper modes.
Setup For Beeper mode:
1. Turn on the TI-25DL power by pressing the key.
2. Press the key to activate the features and settings menu.
3. Press the or key until “bEEP.” is shown on the display.
4. Press the key to change the Beeper mode from “OFF” to “ON.”
Each time the SEND key is pressed the beeper mode will change.
5. Press the key to select the new Beeper mode and return to the
previous measurement mode.
Setup For Alarm mode:
1. Turn on the TI-25DL power by pressing the key.
2. Press the key to activate the features and settings menu.
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