Gentec-EO MACH 6 - Manual (Page 43)

Mach 6 User’s Manual Revision 2.1 43
Missing Pulses
The Mach 6 Applications software is capable of detecting missing pulses in two ways.
Missing pulses below a user set threshold.
When the Search Data for Missing Pulses button is pressed, the current data set is
examined. Any pulses with energy less than the threshold are flagged as missing, and
there time stamps are recorded and displayed. This can be used with internal and external
triggering, but it is most effective when used with external triggering.
Missing pulses due to missing time stamps.
With internal triggering, if the pulse is below the trigger level, no trigger will occur, but
the period timer will still be running. This means that the period will be longer by at least
2x ± the frequency stability of the laser between the pulses adjacent to the missing pulses.
The applications software examines the pulse data for this condition and records the time
stamps where the period is discontinuous. From the continuous period data, the true
period can be found and used to count how many pulses were missing in the
discontinuities.
The % Frequency Stability Threshold setting determines how much time stamp mismatch
is allowed when measuring the true frequency.
Other data analysis may be performed by importing the saved data files into a software
package such as MathCad.
Data Correction
The Mach 6 system is capable of correcting data for wavelength and temperature
variation from the calibration values. Both of these corrections can be disabled if so
desired.
Wavelength Correction
Wavelength correction is done in the Mach 6 instrument. When a wavelength different
from the calibration value is selected, the internal gains of the instrument are changed to
normalize the response of the probe to the calibration wavelength. Since the sensor
responsivity can vary significantly with wavelength, turning Wavelength Compensation
on may cause a rescale of the available ranges. If this occurs, the instrument will set itself
to the currently set range if it is still available. If it is not, the instrument will set itself to
the next available range.