I connect only one instrument to computer via GPIB, But find 20 instrument in max?

[oh my God]

It's the first time I use GPIB card, and I met a problem.

I connect agilent 33220a to NI's PCI-GPIB card in my computer.

In MAX, I choose scan instrument under GPIB,

the instrument show receive a sytax command, and max say instrunment didn't answer *IDN?, I don't know why.

and when I use demos download from ni.com, whatever command I send, I met the same question. instrument receive a sytax command, and computer get a timeout error.

and there is another question, I only connect one instrument to GPIB card, and assign it to GPIB::10, but after I scan instruments in MAX, under GPIB0 it list 20 instruments(GPIB::10-GPIB::30), none of them responce to  *IDN?.

thiank you for your advice,  I really bothered by this problem.

[oh my God]

I change the GPIB bus, and the problem fixed.

and I change it back, and it also works.

the problem is due to I didn't connnect them tightly

[RunningK]

haha!
That's sure the easiest and at the same time hardest problem to fix!!