Gentec-EO MACH 6 - Manual (Page 42)

Mach 6 User’s Manual Revision 2.1 42
minutes of data. Pressing the ARM button again stops data acquisition and the pulses are
now stored in the Mach 6 memory and are ready to be retrieved and analyzed. If an event
occurs during pulse measurement that could potentially corrupt the measurement, then
that pulse will be discarded. The significance of this is that the first pulse of a batch taken
after an arm is always discarded. Since the arm command is sent asynchronous to the
laser pulses, and then the first trigger event after the arm could occur on the tail of the
pulse, resulting in a lower measurement than expected. To avoid this case, the Mach 6
will discard this first measurement. In most cases this is not an issue, but if a set number
of pulses are being sent by the laser, as in a burst mode, then Mach 6 must be set to a
batch size of one less pulse.
Retrieving Data
Press the Read Pulse Memory Button. This control calls a user prompt that asks for the
pulse offset and the number of pulses to retrieve from pulse storage memory. Once that
information is acquired, the pulse memory is read. The destination of the pulse memory is
dependant on the state of the Read to File and Read to Display the check boxes. Note that
both boxes can be checked.
Alternatively, the Auto Read Batch box on the Instrument Controls Tab can be checked.
This will cause the entire measured batch to be automatically read into the selected data
target, files, displays, or both as soon as the batch is taken.
The pulse memory is capable of storing up to 4,194,303 pulses. This is a large volume of
data and it can be time consuming to retrieve all of it at once. The pulse offset and
number of pulses to retrieve controls make this manageable. As an example, suppose
there are 2 million pulses in the memory. The user can ask for this data in batches of
500,000 pulses at a time in 4 batches:
Read 1, pulse offset = 1, number of pulses to retrieve = 500,000
Read 2, pulse offset = 500,001, number of pulses to retrieve = 500,000
Read 3, pulse offset = 1,000,001, number of pulses to retrieve = 500,000
Read 4, pulse offset = 1,500,001, number of pulses to retrieve = 500,000
The response of the application to large pulse batches will depend on the host PC. A test
machine with a 2.66GHz dual core processor and 3GB of memory retrieved 500,000
pulses to a data file in 7.9 seconds. The retrieval to the display took 20.9 seconds. The
extra time is due to the processing of the large data arrays in the application.
Analyzing Data
The Mach 6 Applications Software has 4 data analysis displays. There is a strip chart for
a visual representation of laser stability. There is a Histogram for a visual representation
of the pulse distribution. There is an FFT display that allows the use to look for
interference signals in the data. Last, there is a statistics display that computes commonly
used statistical measurements.