How can I send an SCPI command to just one device on a GPIB bus?

[M_Duguay]

Hi, I am using SCPI to talk to a Kiethly 2000 and a Yokogawa wt 1030 as part of a migration job for a customer.  I know which SCPI commands to send to get the data ":fetc?" and ":meas:val?" (plus the setup commands)  I know this because I found a config file among the files from the old system, the source files however seem to be long gone so I don`t have the whole picture.

What I need to know is how to send a command to only one of the two devices.

As for details:

I don't have the devices with me yet but I will receive them soon.

I am programming in C if that matters (I will be calling the program from our main control software).

I know the basics of SCPI ex: it is ascii sent by GPIB, the commands follow a tree structure...

Any help would be greatly appreciated as I seem to have reached a brick wall.  

Thank you!

[Dennis_Knutson]

When you use the VISA Write, you provide the resource name and the resource name includes the instrument's unique address. Have you looked at the help file?

[M_Duguay]

Hi, thanks for the response Dennis.

I should have mentioned that I am develloping in C for QNX and I'm not using VISA.

What I'm doing is a low level open() pwrite() and pread() to dev/gpib.  

I'm not using any NI software, but this forum was by far the largest and most active on the GPIB subject that I was able to find.

So if anyone is knowledgeable in low level stuff, that`t the kind of help that I'm looking for.

Appreciate the help.

[nyc_(is_out_of_here)]

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@M_Duguay wrote:

Hi, thanks for the response Dennis.

I should have mentioned that I am develloping in C for QNX and I'm not using VISA.

What I'm doing is a low level open() pwrite() and pread() to dev/gpib.  

I'm not using any NI software, but this forum was by far the largest and most active on the GPIB subject that I was able to find.

So if anyone is knowledgeable in low level stuff, that`t the kind of help that I'm looking for.

Appreciate the help.

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This may be the most active on GPIB but it is for NI software.

[M_Duguay]

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This may be the most active on GPIB but it is for NI software.

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Ah yes, I was hoping someone might know somethnig about the lower level workings of GPIB.  Alas, I will continue searching for info, though I am still open to suggestion if anyone has some low level knowledge about GPIB.

On another level, visiting this forum has given me a good impresison of NI software, and I may consider using some on future projects that require this kind of interfacing.

[crossrulz]

I thought you had to supply an address for those commands.  If not, you don't have a good library.  You might want to look up the support for the library you are using.