GPIB-USB-HS

[LarsUlrich]

We have been using the NI GPIB-USB-HS adaptor to control some gpib devices.

We have been looking to buy more, but when looking we also found the GPIB-USB-B, they are pretty much the same except the former is "high speed" and runs at a faster rate.  I was wondering if and when switching to the non-high-speed adaptor could potentially cause me problems. 

[Dennis_Knutson]

Since the -B is obsolete and you cannot buy them from NI, I don't really understand your concern. If you were to run across some used ones, then any HS compatible instruments would just run at a slower rate. f

[LarsUlrich]

We are buying used no matter what, and buying the -B will simply save us money.  Im curious about when the slower data speed is going to start to become an issue, will I notice the slower speed if I am taking measurements in rapid succession, or if I am running multiple instruments?

[Dennis_Knutson]

You will notice a big difference if your instruments are HS compatible. With the slower transmission rate, you will notice some difference on each read and write if the instruments are faster than the 850 Kbytes/s rate of the -B. Personally, I think it would be pretty short sighted to get the -B model.

[mheaney]

Hi,

I have ordered a NI GPIB USB HS device. The product installation guide says;

"Caution 1To connect to GPIB devices that do not share the same ground potential as the

computer, use a GPIB bus expander/isolator or an isolated USB hub. Failure to isolate

different ground potentials can damage the GPIB device, GPIB-USB interface, and

computer."

This sounds frightening! The GPIB bus expander/isolator costs over 1,000$, almost twice the cost of the NI GPIB USB HS device. How common is damage? Can you recommend an inexpensive  isolated USB hub?

Thanks,

Michael

[nyc_(is_out_of_here)]

We use these devices. Just connect them between the PC and the instrument. No worries.

[SunshineDesign]

I have never had a problem using the GPIB interfaces. The HS version has a bus transfer rate of 2MB/sec compared to 1MB/s for the old standard. So you will only notice significant slowdowns when you arte trying to send a lot of data over the bos. If all you aare doing is sending commands, you will not notice much difference. Where you might notice it the most is when you grab trace arrays in rapid succession and you approach the bus bandwidth maximum.

[SnowMule]

Unless you're dealing with big power, you don't need to worry about the isolators.  Most instruments isolate measurement signals from communication signals anyways.

NI puts that there because of the possibility of a ground loop between the instrument and PC's power supply through the USB-GPIB adapter.

[mheaney]

Can you recommend any particular models?

Thanks