10 TN_EE-BA-e-2020
4.3 Zero calibration
Important! The zero calibration function is only accessible in the 'Pulse-Echo'
measuring mode.
To carry out the zero setting, press the key. This is done in almost the same way
as a mechanical micrometer is zeroed. If the instrument is not correctly zeroed, all
measurements made will be incorrectly zeroed by this incorrect base value. When the
instrument is zero-calibrated, a fixed error value is measured and automatically
corrected for all subsequent measurements. The procedure is as follows:
1. The sound generator is plugged into the measuring instrument. It must be
checked whether all plug connections are faultless. The contact surface of the
sound generator should be clean and free of any foreign matter.
2. Press the key to enter the zero mode.
3. Use the and keys to select the sound generator which is currently in use.
Please make sure that the correct sound generator is selected, otherwise
measurement errors may occur.
4. A single drop of the ultrasound contact gel is now applied to the top of the round
metal plate on the instrument.
5. The ultrasonic measuring head must be pressed onto the metal plate in such a
way that it lies flat on the surface.
6. Then the transducer is lifted off the metal plate.
At this point, the instrument has successfully calculated the internal error factor and
will compensate for it in all subsequent measurements. If a zero calibration is
performed on the instrument, it will always use the sound velocity of the zero plate
installed in the instrument, even if a different sound velocity value has been entered to
make current measurements Although the instrument retains the last zero calibration
performed, it is generally recommended to perform it again when the instrument is
turned back on. This is especially true if a different sound source is used. This is to
ensure that the instrument has always been correctly zero-calibrated.
Press the key to interrupt the current zero calibration and return to the measuring
mode.
4.4 Calibration of the sound velocity
In order to be able to make exact measurements, this must be adjusted to the speed
of sound of the corresponding material. Different materials have different sound
velocities. If this is not done, all measurements will be faulty by a certain percentage.
Single point calibration is the simplest and most common procedure for calibrations
that optimize linearity over long ranges (measuring ranges). Two-point calibration
allows higher accuracy at shorter ranges by calculating the zero setting and the speed
of sound.
Note: For one-point and two-point calibrations, paint or coating must be removed
in advance. If this is not done, the calibration result will consist of a kind of "multi-
