keithley 2400/237 trigger

[tast7867]

Hi,

I am trying to set up two Keithley instruments to trigger remotely and make a measurement simultaneously. I have a 2400 set up to trigger a 237, however, the 237 never reads a measurement. I wrote out each specific command to write to the bus. I haven't been able to figure out if the problem has to do with the commands  given to the 2400 or the 237. I have read both manuals, and have used instrument drivers as well, but that didn't work either. Thanks in advance for any help,

Mitch

[johnsold]

1. There is no data dependency between the commands sent to the two instruments, so it is very possible that the 237 is not ready when the 2400 sends the trigger.

2. Is the trigger signal connected via a cable between the two instruments and not shown in your VI?

I am not familiar with the 237 commands.  I suggest that all the commands to set up the 237 be sent first.  Then send all the commands to set up and run the 2400, at least to the :OUTP ON command (or whatever actually generates the trigger).  Next read the data from both instruments. Finally shut down the instruments and close the VISA sessions.

Lynn

[tast7867]

I am attaching a vi where I forced the sequence as you had described. I had put the full one out before just so one could see all the commands at once. The two are linked by an external trigger cable. The 237 will turn its output on, and the trigger light blinks on the front panel of the 237 (waiting for a trigger) but it never receives it. It just stays in that state without making a measurement.

Mitch

[johnsold]

Can you verify with an oscilloscope that the 2400 actually generates a trigger?  I never used the trigger functions so I am not sure how and when it generates the trigger.

Lynn

[tast7867]

Yes, I have hooked up the 2400 to an oscilloscope and have seen that it outputs a trigger.

Mitch

[johnsold]

Mitch,

If the 2400 generates a trigger but the 237 does not respond, it sounds like you have a bad connection or a bad instrument.  Since you see front panel indications that the instrument is waiting for a trigger, it seems likely that you are sending the right commands.

I would look carefully at the manual for the 237.  Sometimes subtle things interfere with the desired instrument response. You might try to check the instrument status or errors to see if it is complaining about what you are asking it to do.

Sorry I cannot offer anything more specific.

Lynn