operate/connect multiple (2) usb/gpib controllers to 1 controller pc

[jljdex]

Hi -

I have a situation where the instruments I need to talk to via GPIB are approx. 25 feet apart. With this
distance I cannot daisy chain them with GPIB cables. Because of this I want to control each of these instruments
via an USB/GPIB controller from the same windows computer.

I assume this shouldn't be a problem (each device has different GPIB address), but the GPIB environment is new to
me & I want to make sure before I buy a couple of your USB/GPIB controller. So two questions -

1. There isn't any limitation for controlling two USB/GPIB controllers from the
same pc/visual basic program, correct

2. Can you please provide me with any documentation/visual basic examples that apply to this. Or,
is it the situation that as long as the devices have different GPIB addresses everyhting should
work as normal?

Thanks you,

Email or call me at -

jacksonj@nextnetwireless.com
952-967-1183

[Wensu]

---

@jljdex wrote:
Hi -

I have a situation where the instruments I need to talk to via GPIB are approx. 25 feet apart. With this
distance I cannot daisy chain them with GPIB cables. Because of this I want to control each of these instruments
via an USB/GPIB controller from the same windows computer.

I assume this shouldn't be a problem (each device has different GPIB address), but the GPIB environment is new to
me & I want to make sure before I buy a couple of your USB/GPIB controller. So two questions -

1. There isn't any limitation for controlling two USB/GPIB controllers from the
same pc/visual basic program, correct

2. Can you please provide me with any documentation/visual basic examples that apply to this. Or,
is it the situation that as long as the devices have different GPIB addresses everyhting should
work as normal?

Thanks you,

Email or call me at -

jacksonj@nextnetwireless.com
952-967-1183

---

HI jljdex, I found this information about the limitations of the physical GPIB connection:

CONFIGURATION REQUIREMENTS
To achieve the high data transfer rate for which the GPIB was designed, the physical distance between devices and the number of devices on the bus are limited.
The following restrictions are typical for normal operation:
A maximum separation of 4 m between any two devices and an average separation of 2 m over the entire bus
A maximum total cable length of 20 m
No more than 15 device loads connected to each bus, with no less than two-thirds powered on


With respect to actually controlling the devices, each must have a unique GPIB address. Examples are not so easy to come by, since developers make custom-fit programs, but I've had good luck obtaining Instrument Drivers through ni.com. These drivers are make and model specific to the instrument in question and often have a "Getting Started.vi" as an example in addition to VIs for configuration and use of the instrument.

Good Luck,
Victor

[AnalogKid2DigitalMan]

How will a USB to GPIB converter solve the distance issue? Unless the PC is between the 2 pieces of equipment?

If I recall correctly, USB has an even shorter length limit, and issues may arise when using 'extender' devices.
If this is your intent, you may want to investigate USB restrictions.

[jljdex]

I had seen an USB/GPIB module from another vendor with an options for longer USB cables (5 - 10 meters).
Other people have now mentioned to me that USB will not span these lengths very well. Seemed like a good idea :).

Jerry

[AnalogKid2DigitalMan]

How about National's GPIB-130 extender (300 meters), GPIB-140A (1-2km fiber optic), GPIB-120A (40m). Do not know of costs, but maybe one of them (-130?) could assist?

[ScottieB]

jljdex,

Interesting problem. If your PC is next to one instrument and the other is 25 feet away, I think the best, least expensive, and most reliable solution is to use a PCI-GPIB or GPIB-USB-HS for the nearby instrument and a GPIB-ENET/100 for the distant one. There is no limitation on having a couple GPIB-USB-HS products in your system, but as was pointed out before, I'm not sure how USB takes to long distances (I would assume it doesn't like them too much).

The ENET/100 will allow you to place instruments anywhere you can run an ethernet cable (100m before you need hubs or repeaters).

Hope this helps!

Scott B.
GPIB Software
National Instruments

[jljdex]

Thanks Scott -

Yes, the ENET GPIB controller looks to be what I need.

Thanks for the reply!

Jerry