keithley 236 measure unit

[havenoidea]

Hello!

I am having some troubles with Keilthley 236 source-measure unit (over GPIB) as it falls into LSN (listener state). I have tried to use the command "ULN" or "IFC", but once the system falls into LSN state, there is no way out and I would have to restart the instrument again. What is worse is that this takes place on a random basis.

Basically, I have open, write, read, close visa sequences and most of time it works fine. The problem is that the system falls into this dark state without any warnning. Do you have any solutions for this?

Also, I have noticed that whenever I was using the Keithley source-mesaure unit, another instrument, spectrum analyzer Agilent 35670A (also over GPIB) seems to have troubles and it also falls in to a "dark" state where it simply sits and wait for the Labview to receive service request (wait for RQS) from the instrument. I noticed that this occurs whenever I use the two instruments together over GPIB (of course with the different addresses). First few runs works fine, but after awhile either Keithley falls into listener state or the spectrum analyzer falls in to wait state.

[Albert.Geven]

The 236 and 237  are not the easiest systems to program.
The 260x series from Keithley is almost perfect.

Be sure to handle all commands in the correct order and don't use srq but keep polling on the status byte.
But not too fast each 10 ms should do it.

You don't need to open and close visa more than once in your program.

And be sure not too send a cmd when there is still data on its way.

[Makoto]

If the Keithley's instrument is in hang-up state ("dark" state as you say) interfering any GPIB bus activities, it seems like due to Keithley's firmware problem.  To escape from the unstable state on the bus, DEVICE CLEAR (viClear()/VISA or ibclr()/NI-488.2M) may be helpfull.  However I don't know if the instrument in hang-up state can accept the DEVICE CLEAR or not. 

And, if you operate Keithley alone without Agilent, does the symptom appears sometimes? or never? If the symptom appears only when both instruments are operating on the GPIB bus, it likely has another reason.

Makoto

[havenoidea]

Ok. problem resolved. instead of using the drivers downloaded from NI, i just created a vi that does a really simple operation. Most of the parameters are set before launching the vi and the source unit does not get into a dark state any more.

thanks for your help.