3 Operating Instructions
© 2019 Thorlabs
27
3.5.4 Externally Triggered Counter
In this mode, the counter is not timed, but controlled (started and stopped) only by an external
trigger signal. The sensitive
trigger edge
(rising or falling) can be selected.
The APD is biased beyond breakdown voltage at any time. After pushing the Start button, the
trigger is armed and waits for the first pulse slope. When the selected trigger edge is detected,
the counter starts photon count until the next trigger pulse arrives. As for this reason, the trigger
period
T
p
defines the
bin length
as well as the time between subsequent bins. This counting
process continues until the Stop button is pressed. The results are displayed graphically and
numerically, see
.
After starting the measurement (Start button), the Alignment display shows the Trigger State
"enabled" and in the status bar appears "Trigger armed".
In externally triggered timed counter mode, an array measurement is possible as well. It allows
high measurement speed by limiting the number of bins; after completing the count is stopped
(
Single Array
) or restarted (
Continuously
) by the GUI. The max. array size depends on the
measurement speed, see section
. The time diagram below illustrates the extern-
ally triggered timed counter mode for a repeated array count of 3 bins each:
13
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Summary of Contents for SPCM A Series
Page 1: ...Single Photon Counting Module SPCMxxA Operation Manual 2019 ...
Page 2: ...Version Date 1 2 27 May 2019 ...
Page 42: ...40 SPCMxxA 2019 Thorlabs ...
Page 43: ...5 Maintenance and Service 2019 Thorlabs 41 ...
Page 54: ...52 SPCMxxA 2019 Thorlabs 6 5 Dimensions Dimensions of the SPCMxxA imperial version ...
Page 55: ...6 Appendix 2019 Thorlabs 53 Dimensions of the SPCMxxA M metric version ...
Page 61: ...www thorlabs com ...
