Acquisition rate is half of trig rate, why?

[TiTou]

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@Christian  wrote:

Unfortunately I don't have access to the SR.

Christian

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How comes?? I can include you in the email list if you want/have time. I mean... if you have the hardware and can try to reproduce the issue that's great!

[Christian Mergl]

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@TiTou wrote:

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@Christian  wrote:

Unfortunately I don't have access to the SR.

Christian

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How comes??

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Other country, different database.

I'll send you a PN.

Christian

[TiTou]

We might have a solution (pointed to me by NI Support), I will be testing it next week (when I have access to the system).

The default ICD file (I believe all ICD files are installed by VAS) for the Basler A504k limits the exposure time range to [250us ; 16500000us] when the camera is in ExSync mode (external trigger).

[TiTou]

No luck... This is being very weird. Here's what happens :

On Windows 7 64bit :

- in free run mode, no particular issue, acquisition works fine for any frequency and exposure time.

- in triggered mode, it will work up to ~2000Hz for any exposure time and then start to be weird about that frequency.

(that's already discribed in the earlier posts)

- in triggered mode, it will work for any frequency if the exposure time is set to the minimum (1 microsecond), the issue is that with such an exposure time you'd need a lighting source comparable to the sun to get a workable image! In theory (an according to the camera's datasheet) for 3900Hz the max exposure time is 220us.

When I was on Windows XP 32bit, the same code was working and my exposure time has always been 160us.

I'm blaming the OS+Software+driver combination.

[GuenterMueller]

Nice work, Titou.
Staring at your image indicator and watching your video several times I was wondering if there is a change in exposure time when you change the trigger rate: I expected all images stable illuminated regardless of the trigger rate. What I see is that there a changes in the shades of gray from acquisition to acquisition although the exposure time seems to be at 160us all the time in your video. Can we be sure that all the acquisitions were done at 160us?

[TiTou]

Well observed!

In triggered mode, you can set the exposure time you want but if the trig rate is too high for the camera to shoot with that exposure time, it shoots with the highest expossure time it can. For some reason in my case I need to trig at 7.8kHz for the acquired frame rate to hit 3.9kHz so god knows how the camera does to set its exposure time...

[TiTou]

I'm going nuts... The only mode I need to use (ExSync Programmable, in which I can set the exposure time) is the only mode in which it doesn't work... And of course on my time base (trig source) the duty cycle can't be changed!

Oh and if anyone want the code it is available on GitHub : https://github.com/AntoineChalons/AcqTest_Win7-64bit.git

[Christian Mergl]

I am just wondering about what the value is if you use "IMAQ Get Camera Attribute" with "Exposure" (as it is named in the icd file) after "IMAQ Start".

Thanks,

Christian

[TiTou]

It says "50000.000000".

Then if I use the Set Camera Attribute to set it to 160, and then read it again it say "160.000000" but it doesn't change the behaviour at all 😞

Thanks for the idea!