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DT9805 USB problems



Hi ,

We use the DT9805 as the data acquisition module of a fire testing instrument. The tests carried out by this instrument are destructive and often at considerable material cost to our end users. We are experiencing a number for customer complaints due to the fact that the DT9805 USB connection drops on average once an hour for our end users causing them considerable problems. This is on a newly supplied instrument.. Tests carried out at the factory with other new, out of the box DT9805 units confirm this problem. We are testing with a direct connection to the PC (i.e. no hub) and have had similar results for both USB 2 and 3 ports. The problem is observed using both our own software and also Measurement Computing's Quick Daq software. In both cases the failure mode is the same. The application freezes and cannot be killed from Task Manager (Access denied). In device manager the DT9805 device disappears  and is replaced by an unknown device which Windows marks as a bad device.


Driver version is 15/1/2019 which appears to be the latest on your site.

Open Layers version  is 7.8.9


This is a problem which has been experienced many times in the past and for which we have never been given a satisfactory solution. However this customer has now escalated to director level and a fix is now imperative for us. The difference is now that we have the problem being reqularly observed with QuickDaq software on several examples of the unit. I have attached some screenshots illustrating the failure mode

Please advise how this matter may be resolved quickly


Best regards


Paul Gruet






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Hello Paul,

I researched issues surrounding the DT9805 dating back to 2016. I found 33 cases, but only one regarding USB connection dropouts, and it was reported by your company October 2019. No others were reporting dropout issues. If you have a new DT9805 that was not put into service or installed into equipment and it is experiencing dropouts, please test it on another computing to confirm the problem. If testing on a notebook computer, make sure the notebook is using the AC power adapter. If the problem persists, contact your distributor and have it sent back for testing. 

If the problem occurs only after the DT9805 has been installed and operated in your equipment, is there a scenario in which the problem occurs? For example, does it happen when the temperature is above a certain level? Does rebooting the computer restore the communication?

Best regards,

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Hi John,

Thank you for coming back to me.

We have found this issue on many examples of the DT9805 old and new. 

Running a long data acquisition. Stopping it, then starting another one is the most likely scenario to cause the problem, but it does equally just occur mid data acquisition at random times.

 Temperature is not an issue, we see the issue at normal room temperature i.e. around 20 degrees c. There are no covers on the instrument which is well ventilated, Although it is a fire test instrument I am running dummy tests so no heating is involved. In any case all electronics are well separated from heated areas.

After the USB has dropped, the calling application (our software or QuickDaq) cannot be closed from task manager.

A soft reboot does not cure the problem and the application is still shown in task manager as running

Only a hard reboot (press and hold the PC power button) closes the application. This to me is consistent with a driver crash/hang where the driver is waiting for a hardware action to complete.

My tests this time around were on a brand new unit after a customer reported this issue with a different (brand new) unit in the field.

It was me that reported the issue in 2019 and it has never been resolved since then, only now we are again getting high level complaints from customers who have been experiencing this issue for a while. 




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Hi Paul,

I want to help, but we have yet to be able to reproduce your issue. We've tested the DT9805 by running it with QuickDaq for several days in a row, stopping and restarting, and it did not lock up the computer. 

Best regards,

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