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Topic Title: Measure Device Latency and Exposure Time Issue
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Created On: 12/18/2016 9:56 PM
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 12/18/2016 9:56 PM
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Forhereyesonly

Posts: 7
Joined: 12/18/2016

We are have been having issues with a function of Volocity for a few years and I would like to see if we could find a solution to the problem. The issue pertains to the exposure times while using the acquisition setup.

Our acquisition is only capturing a single frame with multiple channels. The exposure times for the channels are set prior to the acquisition and are saved. The issue occurs when running the acquisition, some exposure settings saved in the channels are not respected during the acquisition setup. For example in a blue fluorescent channel, the exposure time is set to 1s but when acquiring the shutter is only open for 0.001 seconds and does not capture the specific channel. This issue is usually only seen when running 3 channels but decreases in probability of occurring when dropping to less channels. In an attempt to solve this issue I have attempted to measure device latencies but I get an error when trying to do this.

In the ideal situation, I would like to set the exposure times and get the acquisition running smoothly without having to cancel it because the shutters are closing too quickly. When I notice that the acquisition is not good, I usually stop it. I do notice that the channel's disk icon appears unsaved which means I need to go back into the channel and set the correct exposure amount. Some times to take one multichannel picture I need to take at least 5 acquisition before all channels respect their appropriate exposure times. As you might suspect this gets quite annoying.

We have a Mac 5000 controller that controls the shutter speeds and a manual filters cube that is change through manual intervention pop up window that I have set to work.

Any advice on what is wrong with the device latency measurement or else this sporadic exposure time issue. Let me know if you need any additional information.

 12/19/2016 4:26 AM
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RAH

Posts: 61
Joined: 5/16/2014

What error do you see when attempting to measure device latencies?

What version of Volocity are you currently using and also which version of Dcam is installed? You can find this information by going to the 'Windows' menu > Show session log (with all hardware switched on).

Do you only ever see the problem when you are managing the shutters? i.e. if you go to the Acquisition setup window and choose the option 'don't manage shutters' and run exactly the same acquisition, do you still see the same problem i.e. are all exposure times honoured correctly when shutters aren't being managed? This will tell us whether you are dealing with a hardware latency issue or if it's just a generic problem with the camera exposure settings.

 12/20/2016 5:10 PM
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Forhereyesonly

Posts: 7
Joined: 12/18/2016

Hello RAH,

The error states the following message in the error report log. I though this would be the most important information to share with you.

..."The command could not be completed because there was an unhandled structured exception: access violation reading from virtual address 0x000000010B20278F at Ludl Hardware (x64).dll!397d() (0xC0000005)"...

..."Fault Location: Ludl Hardware (x64).dll!397d() - function address is relative to module load address"...

I am currently using Volocity 5.4.1.

Interesting that you mention about the Dcam. Opened up the session log and there seems to be an issue with the Dcam. Its states the following:

"16:51:53.708 Failed to load module "DCAM Video (x64)" because a shared library is missing"

Any clue how to resolve that issue?

I also noted these items had an error beside it, maybe it can also help you.

16:51:51.167 QuickTime for Windows has not been installed. All QuickTime features will be unavailable. QuickTime can be downloaded from: http://www.apple.com/quicktime/

Hopefully this brings us forwards,

 12/21/2016 7:58 AM
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RAH

Posts: 61
Joined: 5/16/2014

Actually it might that you don't have a Dcam camera, then that message would be normal.

What make and model of camera do you have?

The error eludes to a problem communicating with the Ludl hardware - have you experienced any problems controlling the shutters manually or through the shutter icons in Volocity? If you have, then this might contribute to the issue i.e. if the shutter is sticking or if there is a communication issue between Ludl controller/shutter and the PC/Volocity.

 12/21/2016 8:00 AM
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RAH

Posts: 61
Joined: 5/16/2014

a good test would be to chose to 'don't manage shutters' in the Acquisition setup dialog...if the timing is then honoured and the channels change correctly then we know it's a shutter issue and nothing to do with the camera communication

 12/21/2016 11:43 AM
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Forhereyesonly

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Hello RAH,

Our camera is a QImaging QICAM Fast 1394.

The shutters do not seem to have any issue with when doing it through the Volocity Icon or closing it manually on the MAC 5000 console.

I forgot to mention in my last post that selecting the don't manage shutter icon or any other such as balanced or maximum sample protection did not make much a of difference. Still exposure time is not respected.

The main difference seems to be with the number of channels I am selecting. All works well with 1 or 2 channels but when I add a third one that is when there seems to be a lagg issue.

I have found a temporary work around which involves having 6 channels open. In my case I double the desired channels and in the Timepoint tab I select continue until stop button is clicked. With this setting I have had no issues so far but it takes double the amount of pictures which gives a larger file size. The channels would go as follows if I want to take a tripple fluo images. Green Green Red Red Blue Blue, I don't think the order of color causes a problem but I think having the same channel reapeated twice solves the issue.

I agree with you that the sutter seems to be the problem, but its strange how in two channel there is no problem but when I add the third channel than the issue is present.

Any thought in mind as to what to do to troublehoot the communication error leading to the error in the device latencies error. Maybe with the proper device latencies measurement taken it will solve this issue.

 12/22/2016 4:01 AM
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RAH

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Joined: 5/16/2014

It certainly sounds like a timing issue but not being able to successfully measure the device latencies due to the error makes it difficult to confirm if it's indeed shutter related...but then if it works for 2 channels, I don't see why it wouldn't work with 3, unless the channels have different properties stored in them.

I'd be inclined to use a trial and error approach, by that I mean try to simplify the Acquisition as much as possible. Start with the light paths/channels...what's stored in each, can you simplify them down to just the exposure control and nothing else selected? Then you can add components back one at a time to see what prompts the issue to appear...that said, if it occurs with only the exposure control selected then perhaps it's not linked to the light path settings at all.

Thinking purely about a potential shutter issue, are you on Mac or Windows PC? I know the Ludl connects via serial on Windows but USB on Mac. I'd probably start by turning the entire system off and recable everything up just in case there is a connection issue. You could try plugging the Ludl controller into a different USB port or Serial port (depending on the platform it's installed on), if it's the latter you'll need to make sure you update the Volocity preferences (Edit menu > Preferences > Serial ports) to reflect the physical change in COM port, otherwise it won't be recognised. After re-cabling and moving USB/Serial ports, does the same issue appear when you attempt to measure the device latencies?

The added difficulty here is that you are running an older version of the Volocity software, I'm guessing on an older OS with older 3rd party hardware drivers e.g. for the Qimaging camera - if this were to have been a bug in any of those components it's likely to have been fixed in more recent releases.

Have you contacted the PerkinElmer support team to ask if this was/is a known issue? I believe the email address is informatics.support@perkinelmer.com

 12/22/2016 1:31 PM
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Forhereyesonly

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Joined: 12/18/2016

Hey RAH,

You have proposed some very good troubleshooting steps that I will definetly investigate, especially simplifiying the channels and working up from there.

We have just (few months) switched the computers to Windows 7 computers but if I recall correctly this issue has been there for many years, even when we had Macs before. I will also investigate re-routing all the cable and check the hardware and drivers.

For the moment I have also extended the issue to the Ludl company and I will see if they can suggest an issue with the error seen in the device latences. For the moment the tech thinks it might be because of our RS 232 to USB converted that might be struggeling. But like I said though this issue was also there during the time when we were using the Macs that had the pure USB connection.

Contacting Perkin Elmer Support Team is always a good experience but I am not certain about their ability to help when my Software Maintenance Agreement has expired. Do you know if they still give out a hand even though your SMA is out of date.

Anyhow, for now I have found the 6 channel work around which I am quite satisfied with and I will repost back if I get the device latencies error fixed through communication with Ludl.

Thanks again for your help, I feel as if I am on the track to getting this issue solved.

 1/4/2017 11:04 AM
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RAH

Posts: 61
Joined: 5/16/2014

Good point. Strictly speaking a valid SMA is required to receive technical support from the PKI Tech support team.

Perhaps see what you get back from Ludl and whether the troubleshooting proves fruitful, if not, and your existing workaround is no longer viable, perhaps you can give the PerkinElmer Informatics support team a shot?

 1/12/2017 12:13 PM
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Forhereyesonly

Posts: 7
Joined: 12/18/2016

Hey RAH,

Great suggestions!

Ill post back if I get any progress with the Ludl.

Thanks again,

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