Elcometer 205 Operating Instructions Manual page 23

6.3 KNOWN VELOCITY CALIBRATION
This procedure requires that the operator knows the sound-velocity of the material to be measured. A table
of common materials and their sound-velocities can be found in "Sound velocities of common materials" on
page 47.
1. Press ON/OFF key to switch on the gauge.
2. Press the CAL key to enter calibration mode. If the MM (or IN) symbol is flashing, press the CAL key
again, so that the M/s (or IN/µs) symbols are flashing.
3. Use the UP and DOWN arrow keys to adjust the displayed velocity up or down, until it matches the
sound-velocity of the material to be measured.
4. Press the CAL key once more to exit the calibration mode.
The gauge is now ready to perform measurements.
Note: At any time during the gauge calibration procedure (IN, MM, IN/µs, or M/s flashing in the display),
pressing the PRB-0 key will restore the gauge to the factory default sound-velocity for steel, 5918 m/s
(0.233 in/µs).
To achieve the most accurate measurements possible, it is generally advisable to calibrate the gauge to a
sample piece of known thickness. Material composition (and thus, its sound-velocity) sometimes varies from
lot to lot and from manufacturer to manufacturer. Calibration to a sample of known thickness will ensure that
the gauge is set as closely as possible to the sound-velocity of the material to be measured.
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