Chapter 2. Instrument Setup
DMS Go Operator’s Manual
63
2.5.1a Setting the Probe Zero (PROBE & CAL - ZERO)
TOF values that are started from an artificial point relative to the pulser firing (the initial pulse, IP, or “T0”), must be compensated by a
probe zero offset value to remove the transit time due to the artificial starting position and probe delay lines. This value also allows
adjustment for uneven probe wear and variations in delay lines.
Note:
ZERO is not available when the DETECT MODE parameter specifies a gate-to-gate and multi-echo type measurement, or when the
THICKNESS CAL parameter is set to 2-point mode.
1.
In the
MAIN
menu, scroll to the
PROBE & CAL
submenu using the joystick (
).
2.
Use the joystick (
) to select the function titled
ZERO,
and then to select the zero method. Six options are available:
•
Manual
— This zero method uses the instrument reference block of known thickness and sound velocity to determine the probe zero
offset value for the connected transducer. It is applicable to both single and dual-element contact type transducers, and works with
critical coupling conditions or rough surfaces.
•
Auto
— This zero method automatically determines the probe zero offset value while the transducer is actively coupled to the
material being tested. Zero is taken from the interface echo after the probe was coupled, and then takes the backwall echo. It requires
good coupling conditions, and multiple data acquisitions to determine the TOF to the material interface (the point at which sound
enters the material) and the TOF to material backwall (the point at which sound reflects from the backside of the material). Since it
performs zeroing every time a measurement is taken, it continuously adjusts for temperature changes and delay wear.
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