THORLABS SPCM A Series, Operation Manual

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3 Operating Instructions
© 2019 Thorlabs
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3.5.2 Free Running Timed Counter
In this operating mode, the APD is biased beyond breakdown voltage at any time. The counter
is started / stopped by the internal timer. The timer is programmed via software, this way defin-
ing the
bin length and the waiting time between bins . After pushing the Start button, the timer
begins to control the counter and incident photons are counted into bins until the Stop button is
pressed. The results are displayed graphically and numerically, see
Graphic User Interface .
The Array Mode allows high measurement speed by limiting the number of bins; after complet-
ing the count is stopped (
Single Array ) or restarted ( Continuously ) by the GUI. The max. ar-
ray size depends on the measurement speed, see section Definitions . The time diagram be-
low illustrates the free running timed counter mode for a repeated array count of 5 bins each:
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