Sound Velocity Calibration; Calibration To A Known Thickness - sauter TN-US Instruction Manual

5) The transducer is to be pressed flat against the surface of the control plate. Now
you can see the value 4mm, because the thickness of the control plate is 4mm and
the instrument is calibrated of 4mm.
6) Now the transducer is to be removed from the control plate.
At this point, the instrument has successfully calculated its internal error factor and
will compensate for this value in all following measurements.
When performing a "Zero adjustment", the instrument will always use the sound ve-
locity value of the in-built control plate, even if any other velocity value has been en-
tered for making actual measurements.
Though the last "Zero adjustment" will be stored it is generally recommended to per-
form a "Zero adjustment" whenever the instrument is turned on as well as, if a differ-
ent transducer is used. This way it is ensured that the instrument has been zeroed
correctly.
The key has to be pressed and the Zero adjustment is terminated. The instrument
returns to the measurement mode.

4.3 Sound velocity calibration

In order to performing accurate measurements, the instrument must be set to the cor-
rect sound velocity of the material being measured. Different types of material have
got different inherent sound velocities. If the instrument isn't set to the correct sound
velocity, all the measurements will be deficient by some fixed percentage.
The One-point calibration is the simplest and most commonly used calibration pro-
cedure, optimizing linearity over large ranges.
The Two-point calibration has got higher accuracy over small ranges by calculating
the Zero adjustment and sound velocity.
Note: One- and Two-point calibrations should only be performed on material where
the paint or the coating is removed; if not, it will result in a multi material velocity cal-
culation which is surely deviating from the actual velocity of the material intended to
be measured.

4.3.1 Calibration to a known thickness

1) A Zero adjustment has to be performed.
2) A couplant has to be applied to the sample piece.
3) The transducer has to be pressed against the sample piece, making sure that the
transducer is placed flat on it.
The display now shows any thickness value and the coupling status indicator should
appear steadily.
4) As soon as a stable reading is achieved, the transducer has to be removed. If the
displayed thickness now distinguishes from the value shown while the transducer
was coupled, step 3 has to be repeated.
5) The key has to be pressed to activate the calibration mode. The MM (or IN)
symbol should start flashing.
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