EPWR problem with GPIB-USB-HS

[Tasogare]

Hello!

Usually I've found the answer with Google or from the forums or just being stubborn until I solve the problem but no such luck this time 🙂

Anyway, we have a growing problem with our production because NI GPIB-USB-HS is giving EPWR (28) error and nothing seems to work. It's a random problem that occurs on ~20% of the test PCs. It could disappear for a while if we exchange the GPIB-USB-HS between two testers but the problem resurfaces somewhere else half a day later (we've got like ~25 GPIB-USB-HS's...)

Setup:

- We've got industrial PC's equipped with NI GPIB-USB-HS which is connected to a safety tester.
- During high voltage test we poll safety tester once in a second is it still testing ("STAT?").
- During the test we suddenly get EPWR (28) error and after that we need to disconnect the USB cable or remove GPIB-USB-HS -drivers in order to get things working again (otherwise we get EDVR error when trying to initialize GPIB board).
- We've got latest NI488.2 drivers (3.1.2) and VISA drivers (5.1, 5.4, 14.0, whatever is the correct version for "VISA").
- The power saving options are all set to disable. From Two places. (DOUBLE CHECKED!).
- PC's equipped with GPIB-PCI don't have this problem.

- EDIT: We're using Windows 7

Ps. Right. This wasn't a problem until we changed our code to poll whether safety tester was still testing or not.

Thanks 🙂

Janne Yli-Arvo, Testing Engineer
Vacon Plc, Finland

[DanC12]

Hi Janne,

The error, EPWR 28, is referring to a loss of interface power, this document from the NI website explains this:  http://digital.ni.com/public.nsf/allkb/463FA163E3B9FAA686256EFB00568691#EPWR

Potential solutions are stated at the bottom of the document:

• Take all handles offline and reinitialize the application
• Quit the application and restart the system
• Disable standby and hibernate modes on the PC

I hope this can be of assistance.

Regards,

DanC12

[JasonSmith]

Lke DanC12 said, this indicates that the computer has lost connection to the GPIB-USB-HS. If this isn't due to a power-management event on the computer (it sounds like it is not), then there may be an issue with the computer supplying enough power to the device, causing the device to malfunction.

You can troubleshoot this by introducing a powered USB hub between the computer and the GPIB-USB-HS. This will allow the power to come from the USB hub's power adapter, rather than directly from the computer's USB ports. Hopefully you have a system where this is reproducible enough that you will be able to determine if the hub resolves your issue.

Please let us know how it goes!

Jason Smith

[Tasogare]

Problem isn't fixing the situation after it occurs. Problem is why is this happening randomly. I'm quite sure that our industrial grade PC's are capable of providing enough power for keyboard, mouse and GPIB-USB-HS.

Also, the best solution so far has been exchanging GPIB-USB-HS's between two testers. Makes sense? No.

[JasonSmith]

My suggestion regarding the USB hub was merely to help narrow down the potential cause of the problem, not necessarily as a long-term solution. Since normally the EPWR error occurs when power is lost to the controller (such as when it is unplugged), it makes sense to start by looking at the power source.

I have a couple more questions which may help understand what it happening:

1. When this problem occurs, are there other USB devices being inserted or removed from the system?

2. What is the full part number on the back of the GPIB-USB-HS controllers? The part number should be something like 187965X-01L, where X is the revision letter. Are all your devices the same revision?

3. You said trading the controllers between two machines seems to solve the problem, at least temporarily. Do you find that some of the controllers exhibit the problem, or have you seen the issue with all of them?