termination character during IV sweep with keithley 2600

[sinkovich]

Hello.

I have some labview code to do IV sweeps on a solar cell. 

When I sweep V and measure I, it works beautifully every time. Completely reproducible results.

When I sweep I and measure V, I randomly get 410 interrupts with the printbuffer() vi while reading back the results. 

Upon probing the error wire I find the following details of the error.

Warning 1073676293 occurred at VISA Read in KE26XX.lvlib:Print Buffer.vi->sweepiv_test_2600.vi

Possible reason(s):

VISA:  (Hex 0x3FFF0005) The specified termination character was read.

I have disabled the termination character in the Keithley 2600 intialise vi, but the problem persists. The strange thing is that the code for sweeping V is exactly the same for sweeping I (with the obvious switches in source and measurement). 

It seems like the measurement/source levels are possibly going out of range and causing the sweep to terminate early. But even when I force the ranges to levels that would negate such a problem, I still intermittently get the error.

Any help would be greatly appreciated!

[RavensFan]

Since it is a positive number, it is actually a warning and not an error.

Is this a VISA serial port or a GPIB port you are using?  Are you collecting raw binary data?  Is the termination character enabled?

My guess is that you are collecting raw binary data with the termination character enable, so at random times, the termination character is a byte coming along in the valid data stream.

[sinkovich]

Hi Ravens Fan, thanks for your help.

It is a warning, yes, but it results in my IV plot being complete rubbish.

I am using a GPIB port (sorry, should have mentioned that).

I have disabled the termination character in the Keithley 2600 intialise vi, but the problem persists. There is a chance I have not disabled it properly. Is there a preferred method for doing this?

[RavensFan · Accepted solution]

You can change a property node for termination character and termination character enable at the VISA port.  It is under Message Based settings.  However I haven't work with GPIB to know how it handles things as opposed to serial ports.  I also don't have your Keithley VI's to know what it is going on inside of them.

[sinkovich]

Thanks for the pic, it's helped clarify I've done the right thing. I've also checked all the Keithley 2600 vi's I've used to see if they are resetting it but they seem okay.

I just can't see what is doing this. It's very strange that the V sweep works perfectly yet the I sweep seems to cut short every now and again.

[sinkovich · Accepted solution]

I've just been through all the vi's again, and found that in the keithley printbuffer() vi there is a VISA property node that seems to re-set the termination character. I must have missed it on my first pass through. Sneaky sneaky.

Anyway, turning that off in the printbuffer() vi has solved it.

Thanks for your help, it's much appreciated!