GPIP-USB-HS dosen't work with a USB extension cable?

[Paul@BSH]

I have a new GPIB-USB-HS interface and it works fine when I connect it straight from my PC to an instrument. However, when I try to connect to a different instrument using a USB extension cable, MAX can't detect the instrument.

I want to use the extension cable because this instrument I need to communicate with is a power meter inside of a large power supply cabinet and the GPIB-USB-HS cable just isn't long enough.

I also tried connecting like this: PC > GPIB-USB-HS > GPIB cable > power meter. Same scenerio - Scan for instruments in MAX does not see the instrument.

Has anybody had any luck extending the cable length on a GPIB-USB?

Thanks - Paul

[Tim Fountain]

Paul,
How long is the cable, or is it a "Fry's" USB extender? Another option might be to extend the GPIB side with a longer GPIB cable.

Thanks

- Tim

[JasonSmith]

Hi Paul,

In the second scenario, in which you use an extra GPIB cable to extend the reach of the GPIB-USB-HS, how long is the GPIB cable?  I use my GPIB-USB-HS in that manner all the time without problems.  Does this particular power meter work if you plug the GPIB-USB-HS directly into it?  From your original post it seemed like it may have been another instrument that you actually had working plugged in directly.

Jason S.
National Instruments

[Paul@BSH]

It turns out I had the GPIB address set on the instrument wrong. (I was trying to write to device 1 and I had the device mistakenly setup as device 11.)

So now I can see the device (a yokogawa power meter) but I still can't write/read to it. I get an error from the instrument that I'm sending the wrong command. The odd thing is I'm sending the same commands that I was when using a NI PCI-GPIB card. I think there must be a different defalt setting in the NI 488 config. properties.

[robertphan]

Hi Paul,

I know this is an old thread, but did you ever figure this out? I'm having the same dilemma, so I'm unsure if I should extend the GPIB side or the USB side. Thanks.

[JasonSmith]

A USB extension cable should be fine, as long as it is a quality-made USB 2.0 cable which doesn't cause the overall cable length to exceed the 5m specified in the USB specification.

Low-cost or old cables might not work well at that maximum distance. Powered extenders are available, but my personal experience with these has been poor. The ones I have seen place the "powered unit" at one end of the cable, which still requires exceeding the standard in one direction. If you need to go beyond the allowable length I would recommend a powered USB hub, unless you have a powered extender you know to be reliable.