PocketMIKE Operating Manual
Page iii
velocity of the material being tested. Actual sound velocities in materi-
als often vary significantly from the values found in published tables.
In all cases, best results are obtained if the instrument is calibrated on a
velocity reference block made from the same material as the test piece;
this block should be flat and smooth and as thick as the maximum
thickness of the test piece.
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 evaluating the accuracy of the thickness provided by this instru-
ment. Instruments should always be calibrated before testing, and the
calibration should be checked after testing, to minimize testing errors.
2. Probe Zero Procedure
Probe zeroing is the process of measuring the time of flight of sound
through the transducer. The transducer time of flight is then automati-
cally removed from each measurement so that only the test piece time
of flight is used to calculate and display the thickness value. The probe
zeroing process is performed automatically while the probe is coupled.
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 trans-
ducer 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.
PocketMIKE Operating Manual
Page iii
velocity of the material being tested. Actual sound velocities in materi-
als often vary significantly from the values found in published tables.
In all cases, best results are obtained if the instrument is calibrated on a
velocity reference block made from the same material as the test piece;
this block should be flat and smooth and as thick as the maximum
thickness of the test piece.
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 evaluating the accuracy of the thickness provided by this instru-
ment. Instruments should always be calibrated before testing, and the
calibration should be checked after testing, to minimize testing errors.
2. Probe Zero Procedure
Probe zeroing is the process of measuring the time of flight of sound
through the transducer. The transducer time of flight is then automati-
cally removed from each measurement so that only the test piece time
of flight is used to calculate and display the thickness value. The probe
zeroing process is performed automatically while the probe is coupled.
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 trans-
ducer 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.
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