Olympus 27MG, User Manual, Page: 43 / 98

DMTA-10043-01EN, Rev. C, July 2016
Standard Calibration Measurement 35
5. Standard Calibration Measurement
Before accurate measurements can be made on a particular material, using a
particular transducer at a particular temperature, the 27MG Ultrasonic Thickness
Gage must be properly calibrated.
5.1 Introduction
The 27MG calibration procedure adjusts the gage so that it measures accurately on a
particular material, using a particular transducer at a particular temperature.
Calibration procedures include:
• Transducer zero compensation— Calibrates for the sound transit time in each of
the dual transducer delay lines, which varies from unit to unit and with
temperature. This simple off-block procedure must be done when the gage is
turned on, when the transducer is changed, and whenever the transducer
temperature changes significantly.
• Material velocity calibration or CAL VEL— Done using a thick test block of the
measured material with known thickness or by entering the previously
determined material velocity manually. It must be performed for each new type of
material.
• Zero calibration or CAL ZERO— Done using a thin test block of the measured
material with known thickness. Unlike the first two calibrations, this procedure is
not required unless the best absolute accuracy is demanded (better than ±0.10 mm
[±0.004 in.]). If required, it needs to be done only once for each new transducer
and material combination. It does not have to be repeated when the transducer
temperature changes. Transducer zero compensation will adjust for temperature
changes in the transducer.