KERN & SOHN TN 300-0.01US - Manual (Page 4)

Sauter GmbH
Tieringerstr. 11-15
D-72336 Balingen
E-Mail: [email protected] Tel: +49-[0]7433- 9976-174
Fax: +49-[0]7433-9976-285
Internet: www. sauter.eu
Instruction Manual
TN_US
TN_US-BA-e-1112 4
this is the area directly beneath the centre of the measured
surface.
The below figure is a top view of a typical transducer.
It is pressed against the top with the thumb or the index
finger to hold the transducer in place. Only moderate
pressure is sufficient to keep it stationary. Its surface must
be placed flat against the surface of the material.
Table 3-1 Transducer selection
Model Freq
MHZ
Dia
metr
mm Measurement
range Lower
limit Description
ATU-
US 01 2,5 14 3.0mm 300.0
mm(in steel
40mm(grey
Cast
iron
HT200)
20 For thick,high-
ly attenuating
or
highly
scattering
materials
ATU-
US 09 5 10 1.2mm 230.0
mm (in steel)
Φ20mm×
3.0mm normal
measurement
ATU-
US 10 5 10 1.2mm 230.0
mm(Stahl
Φ20mm×
3.0mm Normal mea-
surement/ 90°
ATU-
US 02 7 6 0.75mm 80.0
mm
(in steel Φ15mm×
2.0mm For thin pipe
wall or small
curvative pipe
wall
ATB-
US 02 5 12 3 200mm
(Stahl)
30 For high tem-
perature (lower
than 300°C)
measurement
3.2 Conditions and preparation of surfaces
At any kind of ultrasonic measurement, the shape and
roughness of the surface being tested are of paramount
importance. Rough and uneven surfaces may limit the
penetration of the ultrasound through the material resulted
by an unstable and therefore unreliable measurement.
The surface being measured should be clean and free of
any small particulate matter, rust or scale. The transducer
must be placed on a flat and even surface. To get it clean
it might be helpful to use a wire brush or a scraper. In more
extreme cases, rotary sanders or grinding wheels may be
used. Care must be taken to prevent surface gouging
which inhibits a proper transducer coupling.
Extremely rough surfaces such as the pebble-like finish of
cast iron will be measured quite complicated. These kinds
of surfaces comport to the sound beam like frosted glass
on light: the beam becomes diffused and scattered in all
directions.
In addition to this, rough surfaces account for an excessive
wear of the transducer, especially when it is “scrubbed”
along the surface. Transducers should be inspected time
by time if there are any signs of abrasion.
If the transducer is worn off on one side more than on the
other, the sound beam penetrating the test material may
no longer be perpendicular to the surface of the material.
In this case, it is difficult to exactly locate tiny irregularities
in the material, as the focus of the sound beam no longer
lies directly beneath the transducer.
4. Operation
4.1 Power on/ off
The instrument is turned on by pressing the key.
The instrument has got a special memory where all
settings are stored even if it was powered off.
4.2 Zero adjustment
The key is used to „zero“ the instrument. It is just the
same way as a mechanical micrometer is zeroed. If the
instrument isn’t zeroed correctly, all the measurements
taken may be in error by an initially incorrect value. When
the instrument is zeroed, this fixed error value is measured
and
automatically corrected for all subsequent
measurements.
The instrument is “zeroed” as follows:
1) The transducer is to be plugged into the instrument in
the way that all connectors are fully engaged.
It has to be checked that the surface of the transducer is
clean and free of any debris.
2) The key has to be pressed.
3) The key and the key has to be used to scroll on
the sensor model currently used. The right choice of the
sensor is of high importance.
4) A single droplet of ultrasonic couplant is to be applied
to the metallic control plate.
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 velocity value of the in-built control
plate, even if any other velocity value has been entered for
making actual measurements.
Though the last “Zero adjustment” will be stored it is
generally recommended to perform a “Zero adjustment”
whenever the instrument is turned on as well as, if a
different 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 correct sound velocity of the