Zero Adjustment; Sound Velocity - sauter TU 80-0.01US Instruction Manual

5.3 Zero adjustment

key is used to „zero" the instrument. It is just the same way as a mechanical
The
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 meas-
urements.
The instrument is "zeroed" as follows:
1) The instrument has to be powered on and the Two-point calibration function is OFF.
The Zero adjustment is disabled in Two-point calibration mode.
2) The transducer had to be plugged in and it has to be made sure that the connectors
are fully engaged. The surface of the transducer has to be checked: it has to be clean
and free of any debris.
3) The model of the transducer set in the instrument has to be changed to the model
currently used.
4) A single droplet of ultrasonic couplant is to be applied to the metallic control plate.
5) The transducer has to be pressed flat against the surface of the control plate.
6) While the transducer is firmly coupled to the control plate, the key has to be
pressed. The instrument will display "ZER" on the operating hint area while it is calcu-
lating its Zero point.
7) After "ZER" disappears, the transducer has 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 veloc-
ity 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 per-
form 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 cor-
rectly.
The key has to be pressed and the Zero adjustment is terminated. The instrument
returns to the measurement mode.

5.4 Sound velocity

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 proce-
dure, optimizing linearity over large ranges.
The Two-point calibration has got higher accuracy over small ranges by calculating
the Zero adjustment and sound velocity.
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