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PNA-X GPIB pass-through commands

Question asked by DHealy on Jul 24, 2019
Latest reply on Jul 29, 2019 by daras

I have an PSG source and EPM power meter connected to the PNA-X via GPIB to run a mixer application.

I have a VEE program that sets the PSG amplitude level and measures the RF output with the power meter so that the LO can be accurately set for the mixer. The PSG RF output is not connected through the rear of the PNA-X as too much power is lost when measured at the front of the PNA-X. It is therefore external to the PNA-X. These were directly connected to the PC initially as it is the controller. However, during the measurement on the PNA-X mixer application, the PNA-X needs to be the controller to sync with the PSG for the swept LO frequency and also perform the calibration of the RF power leveling from the PNA-X. I will also need to grab data after a mixer DUT measurement on the PNA-X and transfer it back to the PC. This threw up the problem of two GPIB controllers on the same bus which is not allowed. To overcome this problem, the GPIB connections had to be physically changed ( not ideal )

I then found out about the GPIB Pass-through configuration. My problem is that when I tried using the GPIB Pass-through SCPI command, I cannot get any data back from the pass-through instruments ( PSG & EPM ). They will go into remote but will not return any information. If this could work, I could set the LO power levels using the PSG & power meter and then allow the PNA-X to take back control of the instruments. The PC will only be required to read back measure mixer data from the PNA-X afterwards.


My configuration is as follows:


PC is connected to PNA-X via GPIB1 (talker/listener) for the VEE automation program ( will need to set LO power level on PSG by reading from EPM & also take data from PNA-X during the measurement of mixer DUT).

PSG & EPM are connected to the PNA-X via GPIB0 (controller) for RF power leveling in PNA-X mixer application and also to sync with the PSG as an external device for the mixer application. The PC has a GPIB card in it. Below are examples of the lines of code I am sending at various stages in the VEE program which is on the PC.


"SYST:COMM:GPIB:RDEV:OPEN 0, 2, 15000"      This works I think as instrument connected to the PNA-X controller goes into remote.

"SYST:COMM:GPIB:RDEV:OPEN?"  This works I think as I get a single digit number back. I can set a variable called PSG_ID which is used in the next command below.

"SYST:COMM:GPIB:RDEV:WRIT "+PSG_ID+",*IDN?" This does not generate an error, so I assume it was sent ok.


"SYST:COMM:GPIB:RDEV:READ? 2" This does not generate any errors, so I assume it was sent ok.

READ TEXT x STR   This causes an error code "420 un-terminated" to appear on the PNA-X screen followed by a timeout 811 error in VEE.

How do I read back data from a pass-through instrument? I would need to be able to write / read from PSG and just read from EPM. This is critical, otherwise I will have to physically change the GPIB connections on the PNA-X to get


Any help is much appreciated.