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Genika Trigger application note
Time stamping strategies
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Mail : [email protected]
SARL au capital de 55 000€ RCS Draguignan : 521 683 193
2
By default Genika Trigger uses Windows internal clock to generate time stamp with 100ns
granularity. But some applications may require a more stringent time stamping than Windows
internal clock. Windows clock may drift unpredictably and may hinder time stamps pertinence over
time. There are two approaches to solve this issue: either to correct Windows clock or to rely on an
external clock.
Case 1: Windows clock drift control.
In that case an external device synchronize Windows clock to avoid drift. Time stamps are generated
by Genika Trigger.
Note: Sync’ing through Internet NTP doesn’t provide high precision clocking. Usual clocking devices
are Stratum clocks, E1/T1 carrier’s line or specific GPS appliance.
Case 2: External trigger generator.
In this second case an external generator with a reliable clock can both trig the camera shutter and
save a time stamp or let Genika Trigger handle the time stamp. In that second case the frame
sequencing is key information to find back the real time stamping information.
AiryLab SARL,12 Impasse de la Cour, 83560 Vinon sur Verdon. Tel : +33 4 92 76 50 89
Mail : [email protected]
SARL au capital de 55 000€ RCS Draguignan : 521 683 193
3
Case 3: External time stamping appliance
Another solution is to intercept the trigger out line of the camera that set off when starting exposure
and shut down when exposure is over.
AiryLab SARL,12 Impasse de la Cour, 83560 Vinon sur Verdon. Tel : +33 4 92 76 50 89
Mail : [email protected]
SARL au capital de 55 000€ RCS Draguignan : 521 683 193
4
Typical Genika Trigger jitter
Below is the typical time stamping jitter graph in a GNK file using an external signal generator set at
37ms (graph show the jitter : inter frame delay, scale is ms/frame number) :
camera 2
39
38,5
38
37,5
37
36,5
36
35,5
35
0
5
10
15
20
25
30
35
40
45
50
Expected time stamp jitter is about 1ms. If the precision required is better, then it is advisable to use
an external time stamping device.
AiryLab SARL,12 Impasse de la Cour, 83560 Vinon sur Verdon. Tel : +33 4 92 76 50 89
Mail : [email protected]
SARL au capital de 55 000€ RCS Draguignan : 521 683 193