Primary address to use in NI MAX when using a GPIB-USB-HS+?

[bpownall]

I'm pretty much an NI / LabVIEW newbie and I'm trying to debug a system someone else set up.

I'm using an NI GPIB-USB-HS+ cable to connect from my Windows 7 PC to a Keysight 34420A Nano-voltmeter.  The 34420A is at GPIB address 22.  (Verified from the front panel.)

I was trying to set up NI MAX to examine the system.  It correctly identified the GPIB-USB-HS+ at GPIB0.  However, when I set the NI MAX's GPIB Primary Address to 22 and did a scan for instruments, I got a "No instruments were found during the instrument scan" message.

More-or-less by chance, I discovered that if I set the GPIB Primary Address to anything OTHER than 22 in NI MAX, the 34420A is found, with an address of "GPIB0::22::INSTR".  See below.

Could someone explain to me why I have to set the NI MAX GPIB Primary Address to something other than 22 in order to find an instrument at address 22?  Is the GPIB Primary Address in NI MAX associated with the GPIB-USB-HS+ interface itself?  Am I having a newbie lack of understanding?  Something else?

[Albert.Geven · Accepted solution]

The normaal gpib adders of the interface wil be 0. The interface and device should have unequal adresses as you already noticed

[bpownall]

Thanks for your response!  Let me try to paraphrase it, to make sure I understand.  (As I wrote, I'm pretty much an NI / LabVIEW newbie.)

The GPIB Primary Address in NI MAX is the address for the GPIB-USB-HS+ interface, not the address for any instruments or whatever that are connected to the interface.

Is this basically correct?

[Albert.Geven]

You hit the nail on top.

[Minions]

It is the same premise as a router.  The router gateway is allocated on the router (I.E. 192.168.1.1) and all other addresses on the router will be something other than that gateway address.  The GPIB bus works the same.  Its Primary address is similar to the router Gateway except it is typically 0.

[bpownall]

Thanks!