MTS Series LX Laser Extensometer - Manual (Page 52)

LX Laser Extensometer
Calibration
Operation 52
Calibration
Important The calibration procedure alters the output readings of the
instrument and must be performed by qualified personnel only.
Note Calibration is performed under software control from the outside of the
unit. It is NOT necessary to access any internal components of the
instrument.
This following procedure sets the slope and offset calibration constants used by
the laser extensometer in calculating the elongation readings. Within the laser
extensometer, the raw internal readings are applied to a linear function of the
form
Y=Mx
where: x is the raw data to be calibrated,
M is the slope correction factor, and
Y is calibrated output.
If desired, the calibration constants can be defeated by following the procedure
described later.
Note Entry into Calibration mode is permitted only when the laser
extensometer is in the (T
2
- T
1
) measurement mode.
Important
Considerations
Before commencing the calibration procedure, be certain to set all operating
parameters properly and allow the laser extensometer to run for at least one hour
to ensure it is thoroughly warmed up. You must perform the calibration for the
measurement type T
2
-T
l
at the exact target distances where you are operating the
laser extensometer. It is recommended that the calibration procedure be
performed in situ with the laser extensometer installed on the test machine and
the calibration fixture installed in place of the specimen.
Handle the calibration fixtures carefully. Keep them clean. It is especially
important to keep the retro-reflective surfaces of the calibration targets clean and
free of any dirt, film, fingerprints, etc.