GPIB-USB > NI 120A ?

[reteb1]

1.

Can still use 28 ( 2 x 14 )  devices if I'll use my NI 120-A GPIB extender/isolator with a NI GPIB USB converter ? ( Instead of max 14 devices of the NI GPIB USB converter itself  ?

2.

What is the difference between GPIB-USB B and HS ? ( different speeds .. ?  if so what speeds ? )

Thanks,

Peter PE1E.

[Dennis_Knutson]

It should not matter if you use a USB controller or any other type. http://www.ni.com/white-paper/3338/en/

The HS uses proprietary technology to extend the speed to 7.9 MB/sec but the instruments must also support the HS standard. Use the HS if you have a choice.

[reteb1]

I see.

Thank Dennis.

Peter.

[sth]

The NI GPIB-120A has a little software quirk.  It will reduce the HS handshaking back to the older slower speed handshaking which is what is expected.  This shouldn't cause a problem in most cases.

BUT the GPIB-120A will respond as a listener on all GPIB addresses.  So if you scan a bus for listeners you will get 31 of them.  If you query for status bytes you will only find real instruments but you have to check more than listener available.

[reteb1]

Thanks sth.

Does this mean that, with my  NI 120-A, its no or hardly any difference between the speed of the B and the HS GPIB USB converter ?

I can buy a cheaper B  than a HS.

Peter. 

[JasonSmith · Accepted solution]

---

@Dennis_Knutson wrote:

The HS uses proprietary technology to extend the speed to 7.9 MB/sec but the instruments must also support the HS standard. Use the HS if you have a choice.

---

I wouldn't call HS488 proprietary at this point, as it has been added to the IEEE standard, but not all instrument vendors have chosen to utilize it.

Even if your instruments do not support HS488 to approach the 7.9 MB/s that Dennis mentioned, you may still get better performance using a GPIB-USB-HS. The speed of the GPIB-USB-B is throttled by the maximum USB 1.1 speed, while the GPIB-USB-HS is a USB 2.0 device. This allows the GPIB-USB-HS to deliver about 1.8 MB/s using the traditional GPIB handshake, if your instrument is able to support it. The GPIB-USB-B could only achieve approximately 1 MB/s. The difference would be most noticeable if you are using instruments which transfer large amounts of data back and forth across the bus.

You should also consider that the GPIB-USB-B has not been produced by NI for many years, so anything you purchase is going to be very old. Even the GPIB-USB-HS was also replaced last year by the newer GPIB-USB-HS+. While still USB 2.0, the GPIB-USB-HS+ has a much faster processor, reducing latency on many operations. It also includes GPIB bus analyzer capabilities, should you ever need to debug at the GPIB signal level.

[reteb1]

Jason,

Thanks, this is very helpful.

So, I renounce buying the cheap B  and buy the HS.

BTW, will my old HP 59401A System Bus Analyzer still work under  HS ?

Thanks again.

Peter.

[JasonSmith]

---

@reteb1 wrote:

BTW, will my old HP 59401A System Bus Analyzer still work under  HS ?

---

While I have not used that particular instrument, all National Instruments GPIB controllers should work with any IEEE 488.1 compliant instrument.

[sth]

---

@JasonSmith wrote:

Even the GPIB-USB-HS was also replaced last year by the newer GPIB-USB-HS+. While still USB 2.0, the GPIB-USB-HS+ has a much faster processor, reducing latency on many operations. It also includes GPIB bus analyzer capabilities, should you ever need to debug at the GPIB signal level.

---

Jason, Please clarify this statement.  From reading the NI marketing materials it appears that the new "replacement" GPIB-USB-HS+ is not supported on the Mac OS X platform.  So will the older GPIB-USB-HS be still marketed or are the Mac users being left in the cold.  Or is the marketing materials just wrong and the current driver will work with the never GPIB-USB-HS+?

[JasonSmith]

---

sth wrote

---

Jason, Please clarify this statement.  From reading the NI marketing materials it appears that the new "replacement" GPIB-USB-HS+ is not supported on the Mac OS X platform.  So will the older GPIB-USB-HS be still marketed or are the Mac users being left in the cold.  Or is the marketing materials just wrong and the current driver will work with the never GPIB-USB-HS+?

---

That material is out of date. At release time it was only supported by NI-488.2 14.0 for Windows, but we have since released GPIB-USB-HS+ support in NI-488.2 14.1 for Mac OS X. This allows it to be used as a replacement for the GPIB-USB-HS on OS X, but the bus analyzer features remain Windows-only.

As for availability of the GPIB-USB-HS, it is currently still orderable, but we expect users will prefer the improved performance and form-factor of the GPIB-USB-HS+.