Dakota Ultrasonics MMX-6 User Manual

Page 17

MMX-6 Ultrasonic Thickness Gauge

6) While the transducer is firmly coupled to the probe-disc, press the

PRB-0 key on the keypad. The MMX-6 will display "Prb0" while it

is calculating its zero point.

7) Remove the transducer from the probe-disc.

At this point, the MMX-6 has successfully calculated it's internal error

factor, and will compensate for this value in any subsequent

measurements. When performing a "probe-zero", the MMX-6 will always

use the sound-velocity value of the built-in probe-disc, even if some other

velocity value has been entered for making actual measurements. Though

the MMX-6 will remember the last "probe-zero" performed, it is generally a

good idea to perform a "probe-zero" whenever the gauge is turned on, as

well as any time a different transducer is used. This will ensure that the

instrument is always correctly zeroed.

Calibration

In order for the MMX-6 to make accurate measurements, it must be set

to the correct sound-velocity for the material being measured. Different

types of material have different inherent sound-velocities. 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