Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing, UT

4.1: Calibration Methods
Calibration refers to the act of evaluating and adjusting the precision and
accuracy of measurement equipment. In ultrasonic testing, several forms of
calibration must occur. First, the electronics of the equipment must be
calibrated to ensure that they are performing as designed. This operation is
usually performed by the equipment manufacturer and will not be discussed
further in this material. It is also usually necessary for the operator to perform
a "user calibration" of the equipment. This user calibration is necessary
because most ultrasonic equipment can be reconfigured for use in a large
variety of applications. The user must "calibrate" the system, which includes
the equipment settings, the transducer, and the test setup, to validate that the
desired level of (1) precision and (2) accuracy are achieved. The term
calibration standard is usually only used when an absolute value is measured
and in many cases, the standards are traceable back to standards at the
National Institute for Standards and Technology.