Gentec-EO QUAD-4Track - Manual (Page 25)

QUAD-4Track User’s Manual Revision 2.1 25
correction coefficients. The results of the correction will be displayed to show the
accuracy of the corrections.
Note that each measurement taken is the average of 16 pulses. This means that the time to
finish the calibration is pulse rep rate dependent.
The measured data from the instrument is nonlinear in response and is also dependent on
the beam shape. The quadrants are symmetric about the center and have excellent spatial
uniformity and matching responsivity, so calibration can be performed in one axis only.
The system calibrates the sensor in the X axis by measuring the data at 9 positions. These
positions are found using the sensor radius. A 9mm sensor has a radius of 4.5mm. The
software will use the closed even value, which is 4mm, then divide it into 8 intervals, or 9
steps or -2.00, -1.50, -1.0, -0.5, 0, +0.5, +1.0, +1.5, and +2.0. .It then uses the known
positions and the measured data to calculate the correction coefficients.
The beam must be at the 0,0 position before performing the calibration, and the Beam
Position must not be Set to Zero by using the Zero Beam control.
Save Coefficients
Saves the Displayed Calibration Coefficients to a user specified file.
Recall Coefficients
Recalls the Calibration Coefficients from a user specified file. These values will then be
used for beam position correction.
Indicators
The indicators are:
Set Position
Measured Position
Coefficient
Calibrated Position
Set Positions
The requested Set Position for each measurement during the calibration.
The Set Positions are determined by computing the closest even integer radius of the
Sensor and then dividing that value by 8. The positive X axis 4 steps plus zero are used to
fit a 7th order polynomial.