KronTalk

Chronos => Chronos User Discussion => Topic started by: schoenitz on September 06, 2023, 08:16:42 AM

Title: timing of external trigger
Post by: schoenitz on September 06, 2023, 08:16:42 AM

Hi,

I'm seeing an unexpected delay when triggering externally via the BNC connector. In a test I'm recording a LED that flashes at 150 Hz for 100 ms. When it stops, I supply a trigger signal. This timing is more or less exact, I checked this with an oscilloscope.

Here's the signal I'm sending (the time axis is in expected camera frames):
(https://www.dropbox.com/scl/fi/on6jqi2xmlr78ydnxpwcd/original_signal.png?rlkey=adr4wx7o6qt0hbt188nmw4snq&raw=1)

The camera is set to record 2000 frames at 8245 fps. However, it doesn't seem to trigger at the time of the trigger signal but ~44 ms (~360 frames) later. The trigger timing in the camera is set to default - all 2000 frames are pre-trigger, and there are no post-trigger frames.

Here's what the camera is actually recording:
(https://www.dropbox.com/scl/fi/xg8ngzeeoftftp4bqla1q/camera_record.png?rlkey=njb6p3o9ejmhey1vqm6nccgi3&raw=1)

Is this expected? What to do about it? What I actually want to do is record 500 frames, and there I can't really tolerate a 360 frame mismatch.

Thanks.