keithley 26xx (2602) continuous measurement as fast as possible

[SKauth]

Hi,

I am currently trying to measure  a pulsating current of about 5ms duration using a Keithley 2602 Sourcemeter. According to the specification I expect that a sample rate of 10 kHz should be possible, which would transfer in 50 readings per pulse. This seems more than sufficient for my purpose.

So I connected the instrument via GPIB and tried the sample programs, starting with "KE26xx Config Source & Measure.vi" and put a while loop around the Measure VI. I was not really surprised seeing now a low sample rate of only about 40Hz. So it seems to me, that bus communication is slowing down my measurements, which leads me to the assumption that I have to use the obviously existent buffer. Unfortunately I could not find neither information nor examples concerning continuous transfer of buffer contents to the PC. Even the examples in the Keithley scripts only consider the case "Configure > Measure and save to buffer > transfer > done". So it seems I need some kind of handshaking or interrupt routine. Some simple polling solutions I tried so far did not work sufficiently, probably due to GPIB communications blocking each other.

As I'm not very experienced in instrument driver programming, I would appreciate any advice on how to implement this properly so that I don't get any strange error messages or miss parts of the signal.

Also: Why is  the instrument  producing a Queue empty error message, when there is no error? 

cu,

Simo

[Albert.Geven]

Hi

What you try to do is possible on the 26xx, but not easy to program.

In fact you should program the internal (script) to do a measurement and put it in a buffer, and the interface (gpib) to read the buffer or send the buffer autonomously to the pc.

I programmed a bit with this machine and although it is m uch better than the 24xx series in speed Keithley still has not found out how to explain what happens inside in an understandable wa.

It probably is easiest to ask the keithley guys how to build what you try to do.

[timhStanford]

Can you please send an example labview vi that writes a script and reads the buffer to the keithley 26xx?  tholme (at) stanford (dot) edu.  I am having trouble doing exactly that.

My latest stumbling block is a queue full error, #350.  What is that?

Thanks,

[Albert.Geven]

That queue is either the buffer to the instrument but probably the buffer in the instrument that is not read fast enough.

attached are 4 vi's I used. They can be added to the keithley driver for the 26xx series.

But be careful, you now can load and  run a script, the difficult part is to build a correct script and I'm still not sure that what I did was a good way of operating the device although it worked.

good luck