DMTA-10022-01EN, Rev. C, January 2015
Chapter 5
54
d)
Press
[MEAS]
to automatically recall the setup parameters for the chosen
setup and return to the measurement screen.
5.2
Calibration
Calibration is the process of adjusting the instrument to perform accurate
measurements on a particular material at a given temperature using a known
transducer. Calibration of the instrument is always necessary prior to inspection of a
specific material. The measurement accuracy is only as accurate as the calibration
performed.
The following three types of calibration must be performed:
Transducer zero compensation (
[Do ZERO]
)
For dual element transducers only, calibrate for the sound transit time in each of
the dual transducer delay lines. This compensation varies in each transducer unit,
and with the temperature. The transducer zero-compensation procedure must be
performed whenever the unit is powered on, the transducer is changed, or the
transducer temperature changes significantly (see “Setting Up the Transducer” on
page 51 and “Transducer Zero Compensation” on page 58).
Material sound velocity calibration (
[CAL VEL]
)
Perform a velocity calibration using a thick test block of the measured material,
and of known thickness, or by manually entering a previously determined
material sound velocity. You must perform this procedure for each new measured
material (see “Calibrating the Instrument” on page 55 and “Material Sound
Velocity and the Zero Calibrations” on page 59).
Zero Calibration (
[CAL ZERO]
)
Perform a zero calibration using a thin test block of the measured material, and of
known thickness. Unlike the transducer zero compensation and the material
sound velocity calibration, this procedure is not required unless you need the best
absolute accuracy (better than ±0.10 mm or ±0.004 in.). The procedure only needs
to be performed once for each new transducer and material combination. It is not
necessary to repeat the zero calibration when the transducer temperature
changes; transducer zero compensation is responsible for that task (see
“Calibrating the Instrument” on page 55 and “Material Sound Velocity and the
Zero Calibrations” on page 59).
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Страница 157: ...DMTA 10022 01EN Rev C January 2015 Configuring the Instrument 147 Figure 8 3 The COMM screen...
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