DMTA-10022-01EN, Rev. C, January 2015Chapter 554d) Press [MEAS] to automatically recall the setup parameters for the chosensetup and return to the measurement screen.5.2 CalibrationCalibration is the process of adjusting the instrument to perform accuratemeasurements on a particular material at a given temperature using a knowntransducer. Calibration of the instrument is always necessary prior to inspection of aspecific material. The measurement accuracy is only as accurate as the calibrationperformed.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 ofthe dual transducer delay lines. This compensation varies in each transducer unit,and with the temperature. The transducer zero-compensation procedure must beperformed whenever the unit is powered on, the transducer is changed, or thetransducer temperature changes significantly (see “Setting Up the Transducer” onpage 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 determinedmaterial sound velocity. You must perform this procedure for each new measuredmaterial (see “Calibrating the Instrument” on page 55 and “Material SoundVelocity 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 ofknown thickness. Unlike the transducer zero compensation and the materialsound velocity calibration, this procedure is not required unless you need the bestabsolute accuracy (better than ±0.10 mm or ±0.004 in.). The procedure only needsto be performed once for each new transducer and material combination. It is notnecessary to repeat the zero calibration when the transducer temperaturechanges; transducer zero compensation is responsible for that task (see“Calibrating the Instrument” on page 55 and “Material Sound Velocity and theZero Calibrations” on page 59).
