Material Calibration - DAKOTA ULTRASONICS MMX-7 Operation Manual

Dakota Ultrasonics
6) Press the OK key to perform the zero, or ESC key to cancel the probe zero
process.
7) Proceed to the calibration section.
Note: The value that is displayed will change depending on the current velocity
setting in the MMX-7. Disregard the number that is displayed. It is not
important. What is important is accurately performing the steps outlined above
to insure reliability of the probe zero calculation.

6.3 Material Calibration

In order for the MMX-7 to make accurate measurements, it must be set to the correct
sound velocity of the material being measured. Sound will travel at different speeds
in different material types. For example, the velocity of sound through steel is about
0.233 inches per microsecond, versus that of aluminum, which is about 0.248 inches
per microsecond. If the gauge is not set to the correct sound velocity, all of the
measurements the gauge makes will be erroneous by some fixed percentage.
The One Point calibration is the simplest and most commonly used calibration
method - optimizing linearity over large ranges. The Two Point calibration allows for
greater accuracy over small ranges by calculating the probe zero and velocity. The
MMX-7 provides four simple methods for setting the sound-velocity outlined below:
Known Velocity
If the material velocity is known, the user may wish to simply enter the velocity
number into the MMX-7, rather than have the MMX-7 calculate the velocity value
using a known thickness on a material sample. The steps for entering the velocity
are outlined below:
Using a Known Material Velocity
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