KERN & SOHN TN 60-0.01EE - Manual (Page 9)

TN_EE-BA-e-1410 9
3) Use the key and the key to scroll to the probe model currently being used.
Be sure to set the right probe model to the instrument. Otherwise, there will be er-
rors or deviations.
4) Apply a single droplet of ultrasonic couplant to the face of the metal probe disc.
5) Press the transducer against the probe disc, making sure that the transducer sits
flat against the surface.
6) Remove the transducer from the probe disc.
At this point, the instrument has successfully calculated its internal error factor, and
will compensate for this value in any subsequent measurements. When performing
an “instrument zero”, the instrument 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 instrument will remember the last “probe zero”
performed, it is generally a good idea to perform an “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.
Press while in probe zero mode will stop current probe zero operation
and return to the measurement mode.
4.4 Sound Velocity Calibration
In order for the gauge to make accurate measurements, it must be set to the correct
sound velocity for the material being measured. Different types of material have dif-
ferent inherent sound velocities. If the gauge is not set to the correct sound velocity,
all of the measurements the gauge makes will be erroneous by some fixed percent-
age. The One-Point calibration is the simplest and most commonly used calibration
procedure optimizing linearity over large ranges. The Two-point calibration allows for
greater accuracy over small ranges by calculating the probe zero and velocity.
Note: One and Two point calibrations must be performed on material with the paint
or coating removed. Failure to remove the paint or coating prior to calibration will re-
sult in a multi material velocity calculation that may be different from the actual mate-
rial velocity intended to be measured.
4.4.1 Calibration to a known thickness
Note: This procedure requires a sample piece of the specific material to be meas-
ured, the exact thickness of which is known, e.g. from having been measured by
some other means.
1) Perform a Probe-Zero.
2) Apply couplant to the sample piece.
3) Press the transducer against the sample piece, making sure that the transducer
sits flat against the surface of the sample. The display should show some thick-
ness value, and the coupling status indicator should appear steadily.
4) Having achieved a stable reading, remove the transducer. If the displayed thick-
ness changes from the value shown while the transducer was coupled, repeat
step 3.
5) Press the key to activate the calibration mode. The MM (or IN) symbol should
begin flashing.
6) Use the key and the key to adjust the displayed thickness up or down, until
it matches the thickness of the sample piece.