GE CL 5

0-6 Issue 01, 04/05 CL 5
Important Notice
Operators should also be aware that the sound velocity
may not be constant in the material being tested; heat
treating, for example, can cause significant changes in
sound velocity. This must be considered when eval-
uating the accuracy of the thickness provided by this
instrument. Instruments should always be calibrated
before testing, and the calibration should be checked
after testing, to minimize testing errors.
2. Probe Zero Procedure
When performing a one-point calibration with a contact
probe, the probe zero procedure must be performed as
described in this manual. The probe zero block should
be clean, in good condition, and without noticeable
wear. Failure to properly perform the probe zero
procedure will cause inaccurate thickness readings.
3. Effects of Temperature on Calibration
Temperature variations change the sound velocity of
materials and transducer delay lines and, therefore,
calibrations. All calibrations should be performed on-
site, and with test blocks at the same temperature as
the test piece, to minimize errors due to temperature
variations.
4. Transducer Selection
The transducer used in testing must be in good
condition without noticeable wear of the front surface.
Badly worn transducers will have a reduced effective
measuring range. The specified range of the transducer
must include the complete range of thicknesses to be
tested. The temperature of the material to be tested
must be within the transducers temperature range.
5. Use of Couplants
Operators must be familiar with the use of ultrasonic
couplants. Testing skills must be developed so that
couplant is used and applied in a consistent manner to
minimize variations in couplant layer thickness and
errors in test results. Calibration and actual testing
should be performed under similar coupling conditions,
using a minimum amount of couplant and applying
consistent pressure on the transducer.
6. Doubling
Ultrasonic thickness gauges will, under certain
conditions, display readings which are twice (or, in
some cases, three times) the actual material thickness
0-6 Issue 01, 04/05 CL 5
Important Notice
Operators should also be aware that the sound velocity
may not be constant in the material being tested; heat
treating, for example, can cause significant changes in
sound velocity. This must be considered when eval-
uating the accuracy of the thickness provided by this
instrument. Instruments should always be calibrated
before testing, and the calibration should be checked
after testing, to minimize testing errors.
2. Probe Zero Procedure
When performing a one-point calibration with a contact
probe, the probe zero procedure must be performed as
described in this manual. The probe zero block should
be clean, in good condition, and without noticeable
wear. Failure to properly perform the probe zero
procedure will cause inaccurate thickness readings.
3. Effects of Temperature on Calibration
Temperature variations change the sound velocity of
materials and transducer delay lines and, therefore,
calibrations. All calibrations should be performed on-
site, and with test blocks at the same temperature as
the test piece, to minimize errors due to temperature
variations.
4. Transducer Selection
The transducer used in testing must be in good
condition without noticeable wear of the front surface.
Badly worn transducers will have a reduced effective
measuring range. The specified range of the transducer
must include the complete range of thicknesses to be
tested. The temperature of the material to be tested
must be within the transducers temperature range.
5. Use of Couplants
Operators must be familiar with the use of ultrasonic
couplants. Testing skills must be developed so that
couplant is used and applied in a consistent manner to
minimize variations in couplant layer thickness and
errors in test results. Calibration and actual testing
should be performed under similar coupling conditions,
using a minimum amount of couplant and applying
consistent pressure on the transducer.
6. Doubling
Ultrasonic thickness gauges will, under certain
conditions, display readings which are twice (or, in
some cases, three times) the actual material thickness