One Keithley Current Vs Time for two resistors

[Klor]

Hey Everyone,

I'm rather new, allow me to introduce myself. I'm Jason, a student from Cambridge Uni.

As a chemist, who's now dabbling in engineering. My task is to create a lab script that is probably quite common for some of you.

Logically I've put it in (please see attached image). The keithley has two ports on the front and the back end, that can attached to two separate resistors and thus give two different current vs time measurements on xy graphs. They can be taken almost simultaneously.

I'm about to make a script and block diagram. If anyone can advise me on this that'd be great. Or if there's already an example script out there that does essentially this, that's even better.

What Have I Done So Far?

I have all the necessary drivers and a colleague has made a script for multiple instruments (single measurement acquisition for each). My thinking is to use that and create a time delay between the two different ports and have that in a loop. 

Best,

Jason

[GerdW]

Hi Klor,

My thinking is to use that and create a time delay between the two different ports and have that in a loop. 

That's a good idea!

Your Keithley surely knows a command to switch between FRONT and REAR connector, so you need this command followed by a resistance measurement…

[cstorey]

You're on the right track, and I don't want to complete your home work for you, but I will offer advice.

The K2400 has an auto-ohm resistance measurement feature, USE IT, but set limits if your resistors have current or power limits below 20V/100mA/2W. See section 4 or the K2400 user manual, pg 111, https://mm.ece.ubc.ca/mediawiki/images/2/26/K2400Manual.pdf

Enable auto-zero, auto-settle, auto-ranging for the measurements unless speed is critical.  A typical resistance measurement takes <100ms with them enabled. 

I'd suggest using 4-wire (remote sensing) to remove the resistance of your cables/connectors from your actual measurement unless you are confident that the resistance you are measuring is >>> bigger than those parasitics.

I'd use the Keithley internal timestamp to track the time your measurements front/back.

Attached is the config I use for auto-ohm measurements, all subvis are from the K2400 driver except the other attached vi that is used to limit the current used for making resistance measurements.  Apparently there was no driver for that so I just implemented the right SCPI commands.

Post some code if you need help.

[Klor]

Dear GerdW,

After a whole day of searching I can't come across it.

I'm completely new to the field and the comparison between back panel and front panel is extended to the Keithley and also inherent in LabVIEW.

I'm using a GPIB and would expect it to be a simple command to swap between them?

However looking into it, looks like a huge chain of commands.

[Klor]

Hey Cstorey,

I believe the limits are built into the code that my colleague previously created.

The 4 wires would be difficult if there's only one circuit wouldn't it? 

Just to clarify, I'm a student in the PhD sense, and the cross breeding of the field has meant chemistry must be introduced to electricity :P, it's not homework, more an obstacle to research!

I thank you for your example, however there seems to be other VIs missing so there's an error.

The code I post here is my colleague's for multiple instruments.

He has it to view the address first and use that to take measurements and then export them to an X-Y. 

In my opinion the thing that needs changing isn't the KE24XX settings, this states will voltage/current be the source and will the other be the measured value.

Leading onto KE24XX ON, which to me seems like the only thing that needs changing. In this area it is decided which instrument is being used, then a time delay is incurred to separate the two instruements and then a reading is taken and exported to a graph.

All that seems to be needed is to swap the "address" to the back panel ports. But I have no idea how to do that.

Would you agree?

[Klor]

Update!

Sorry for the spam. I can't seem to edit my previous posts.

The command is :

:ROUTe:TERMinals <name>

<name> = FRONt Front panel in/out jacks REAR Rear panel in/out jacks

So, I think setting two instruments to the same address but naming them differently would work?

[cstorey]

Ah, when you mentioned drivers downloaded I assumed you were using the nicely packaged Keithley 2400 instrument driver.  It does simplify life.  Its found here -

There's nothing wrong with your colleagues vis, they use the SCPI commands that set the instrument into different states, turn ON/OFF the output, and switch the terminals FRONT/REAR as you pointed out.

Here's a full example using the Keithley driver.  First unzip the download and then put it either in <LABVIEW DIR>/instr.lib or in the same directory as my code.  Then you can open my code (top level vi is - k2400_front+rear_resistance_measurements.vi).  When you do that a bit of searching will occur and once all files are located it should be good to go. 

You can customize as you like.

[Klor]

This looks amazing Cstorey,

I'm missing "Close.vi" and "Select Active Terminals.vi"

I'm very much a novice and going through the 89 page labview manual. But if I'm doing something stupidly obviously wrong, please let me know.

Best wishes,

Jason

[Klor]

This was fixed by downloading the K24XX drivers from here:

http://sine.ni.com/apps/utf8/niid_web_display.download_page?p_id_guid=25B255F3AA83660EE0440003BA7CCD...

Rookie mistake

[cstorey]

Sorry, meant to supply that link!

89 page manual?  You might want to invest some time exploring the resources list in this thread..

https://forums.ni.com/t5/LabVIEW/Learn-labview/m-p/3132435

Let me know how it works.

Craig