05-26-2011 05:55 PM
We have a PC-6733 analog output setup that has been working pretty well now for a couple years. However, we recently noticed very large errors, on the order of 200mV at +/- 9V. It appears to be a gain error (reversing polarity of output produces a gain error, not an offset or noise error). It also seems to drift in time, but the physical strain of the cable definately plays a large role.
This is very disturbing when a $2000 piece of equipment can't handle a little bit mechanical strain.
I am pretty sure it is not the PCI connector, as those signals are digital - unless it is some kind of grounding issue - but the card is now securely connected at the screw that holds the metal slot filler to the rear of the computer case.
The cable connector was loose at the metal case slot filler, so I tightened the cable screw socket screws down to secure it. This did seem to help a little, but the errors are still relatively big. Also wiggling the front corner of the board (farthest from the cable and PCI connector) a little bit produces similiar effects.
Also, reversing the cable did not change anything, and whatever end is plugged to the breakout box is not affected by mechanical strain - it is definately something at the PCI card.
05-27-2011 12:12 PM
Hi, this is Paul with Applications Engineering at National Instruments.
First off, I would like to clarify when this problem developed. Have you always experienced this problem or has it developed recently? What has changed in your system since you began experiencing this?
What is causing stress on this card, and what can you do to eliminate this stress? Could you develop a way to reduce the cable's stress on the PCI card? Do you possibly need a longer cable so that you have more cable to work with?
Our PCI cards our designed to remain stationary, and not designed to endure significant amounts of stress on them. Over time, this stress may have caused damage to your card in the form of loose connections or connections or components becoming stretched. Additionally, this flexing of the actual board may cause a change in resistance in some of the components of the board, which could cause these fluctuations.
Regards,
05-27-2011 03:53 PM
@Paul-D wrote:
Hi, this is Paul with Applications Engineering at National Instruments.
First off, I would like to clarify when this problem developed. Have you always experienced this problem or has it developed recently? What has changed in your system since you began experiencing this?
What is causing stress on this card, and what can you do to eliminate this stress? Could you develop a way to reduce the cable's stress on the PCI card? Do you possibly need a longer cable so that you have more cable to work with?
Our PCI cards our designed to remain stationary, and not designed to endure significant amounts of stress on them. Over time, this stress may have caused damage to your card in the form of loose connections or connections or components becoming stretched. Additionally, this flexing of the actual board may cause a change in resistance in some of the components of the board, which could cause these fluctuations.
Regards,
05-31-2011 03:58 PM
I just wanted to let you know that I am still reviewing this issue with our R&D department, and should have a response for you soon.
Thanks,
05-31-2011 04:42 PM
Thank you, I appriciate it.
- Judson
06-01-2011 11:08 AM - edited 06-01-2011 11:10 AM
Judson,
This sounds like a grounding issue given that all of the channels change at the same time. Try pulling out the board and take a look at the screws on either side of where the I/O connector connects with the PCI board (they make the CHSGND connection). If they are loose then tighten them.
Let us know how that works out for you. If these are secure as well as all of your other connections and your problem wasn't resolved, its possible you may have damaged a trace or connection on your board with all of the flexing. This would be consistent with the problem only occuring when the cable is moved around, in that it may possibly be opening the ground connection, which would explain the floating values. We do offer repair options for our products.
Thanks,
06-07-2011 05:22 PM
Before I made the initial post we did notice that the connection between the cable connector housing and the case slot filler was loose as you describe. We tightened it down (which caused another issue I will explain below), and we thought we had cured the problem, but it did not completely solve it. There is definately more to this, and I would like to send it in for repair. I am not sure if you should give me a case number that I can take to your repairs department for reference? I will wait for a response from you on how to appropriately proceed.
With regard to tightening the socket screws that secure the pci card -> cable connector to the slot filler metal: When we did this, the female screws are of the design such that you can tighten them with a flat head screw driver. The type on this card has a round outer jacket, and a slot across the female end. When we tightened the screw down into the connector receptical, the metal deformed. Because this metal intersects the female part of the screw, it caused the inner threads of this female screw to deform. Now I cannot screw the cable screws into it properly. See the attached picture. I'm not pleased with this design, because it is inevitable that the female screws will come loose sooner or later, and tightening them can cause this problem. I would prefer the screws to be spaced out further so you could use a female screw with a hexagonal outer profile so that the female threads will not be affected by tightening them into the receptical body.
Anyways, thank you for any assistance. I am hoping to resolve this affordably with some confidence this won't be a recurring problem.
06-08-2011 01:07 PM
Judson,
I have private messaged you about your repair options.
In regards to your concerns, our R&D department browses these boards, and I will also bring this to their attention. I don't have any direct solution for you on this at this time.
Thanks,
06-08-2011 04:25 PM
Paul,
I approved him for an RMA and we talked with the coordinator and he is going over the options