Both HP3458A returning "MEMORY EMPTY"

[Tina2]

Hello.

I have two HP3458A connected with just one GPIB-USB-HS card to PC which makes one of HP3458A master and second one a slave.

My subVI for frequency measurement works independently when running separately on first Hp and separatey on second one.

But when I shoud measure frequency on both HPs at the same time (in same VI), I'm getting memory empty.

I think this is in relationship with triggering options.

I should set synchronous triggering on both of them, but I'm not sure which trigger option should be in this state? (TARM, TRIG or NRDGS).

Because I do not trigger, I do not have nothing to read. While Querying, MCOUNT? returns 0, and RMEM has 1,0 as parameters. 

How can I solve this problem? TARM and TRIG have SYNC options, but it didn't help.

Christyine.

[Eric_K]

Christyine,

It seems like which of these options are necessary should depend on your instrument, and should be documented with the instrument.

Are you using the driver available at:

http://sine.ni.com/apps/utf8/niid_web_display.download_page?p_id_guid=E3B19B3E90EB659CE034080020E748... 

for your application?

Eric K

Applications Engineering

National Instruments

Message Edited by Eric K on 03-04-2009 03:07 PM

[Albert.Geven]

Hi

You are writing one is master the other slave, but on the gpib both have to be slave to the pc!

[Tina2]

Dennis, thank You for your reply.

Can You explain in more detail.

Thanks.

[Eric_K]

I think Albert was simply trying to point out that when connecting you two HP3458A's to your PC using your GPIB-USB-HS, your PC becomes the master in the system, and your HP devices both become slave devices in the system.  So your system actually has 2 devices on the bus, your PC and the two HP3458's.

Eric K

Applications Engineer

National Instruments

[Albert.Geven]

Thanks Eric

Only you mean three devices on the bus.

The master is the pc (normally with gpib address 0

Both HPs are slaves and need different gpib addresses and these addresses should not be 0.

sorry for my too short earlier answer

[Tina2]

Hi, Albert. Sorry, I substite You earlier for Dennis.

When I connect two HPs with one GPIB card to PC, initialy they become same GPIB Interface IDs (which is one) and different addresses. Is this ok?

Then I use SendList to reset both HPs. This works.

After, I try to read both freqs from HPs at same time and then this memory empty occurs. 

[Albert.Geven]

Hi

How do you address two gpib addresses at the same time.

The bus can trigger both devices at the same time but you can only read from one address at one time. You always can read them fast after another.

[Tina2]

SendList has option to address more then one instrument.

[Albert.Geven]

You are right but probably the hp cannot handle this correctly.

So try to send them apart and see what happens.

I'm using only the visa functions, not the gpib functions anymore.