Problem using the Keithley 6487 pAmmeter with voltage supply.

[CameronDean]

   I am trying to use a Kiethley 6487 to bias a photon detector in my lab and I am new at LabVIEW. So far I have been able to get current readings from the ammeter but I am unable to ramp up the voltage supply. The code I have came up with so far is able to start remote communications with the device but returns an error when using the ramp vi. Here is the error I am recieving:

Error -1074135024 occurred at KE6485 Configure Source Ramp.vi

Possible reason(s):

Driver Status:  (Hex 0xBFFA0010) Invalid value for parameter or property.

I have removed the piece of code related to the biasing from my main block diagram and changed my global variables to constants. Any help with this matter would be much appreciated.

Thanks
Cameron

[Albert.Geven]

You probably give a wrong value out.

[Tori.M]

Hi CameronDean,

Thanks for attaching your coding. Unfortunately, it's not possible to run the VI for myself without the Keithley drivers installed so each of the subVIs appears as greyed out.

However, looking at the error that you're receiving, this is occurring at "Configure Source Ramp.vi" which is the VI to the far right. As the error suggests invalid value for parameter, I'd recommend checking your inputs of numeric constants 0, 5 or the output from the "Step Count.vi" as one of these is likely to be the wrong parameter (i.e. wrong value).

To check the output of the Step Count.vi, I'd recommend replacing this with a constant to see if the error still persists.

Another way of debugging is to turn on context help (Help >> Show Context Help) then hover your mouse over the subVI "Configure Source Ramp". In the dialog box that appears do you get an option for "Show Detailed Help"? If so please click on this as detailed help for this function may suggest allowed and disallowed parameters for this subVI.

Hope this helps!

[CameronDean]

Thank you for your replies. You were right, I was giving the wrong value for the Configure Source Ramp vi. As I am new at this I was unaware that all I had to do was click "Create Constant" on the vi and was attempting to guess the value required. I've managed to get the vi's working.

Thanks again
Cameron

[ainat]

Hi Cameron,

I am using Keithley 6487 to source voltage and measure current. Although I have been able to source the volatge. but I am unable to measure the current.

Will it be possible for you to post you full code. I guess its kind of similar to what I want to implement. It will be really helpful.

Many Thanks!

[CameronDean]

Hi ainat

Here is the code that I used to get a current reading from the 6487. You'll need to check with MAX that the GPIB port is correct in the Block Diagram but I think that the standard 6487 GPIB number is 22 so everything should work.

Cameron

[ainat]

Hi Cameron,

Thanks for the code. But I am not sure how you are trigerring the instrument to measure the current as I don't see any code for that.

Is it that you only do a zero check and then read the data coming out?

Thanks

Ainat

[CameronDean]

Hi ainat

I'm a little rusty on excatly how I built this vi as it was over a year ago but if memory serves, as the 6487's standard use is for current readings all you need is to send the command ':READ?:' and the vi should give the measurement on the FP. I was using this vi as a sub-vi so it doesn't have the prettiest FP but it should give a current value in nA. I also checked how the vi ran with a 6487 connected to a WinXP machine and it was running fine.

I think that the last vi I sent didn't contain the sub-vi for zeroing the pAmmeter so I've enclosed a zip file with all the vi's I either creater or obtained from Keithley. If you're trying to source a voltage from the pA and take current reading then I would recommend using the vi's I wrote (CurrRead, CurrRead14 etc) as the Keithley vi's will turn off the voltage source when trying to take a current reading.

Sorry about the late reply, I think our time zones are a bit out of sync but hopefully this will sort your problem.
Best of luck
Cameron

[ainat]

Hi Cameron,

Many many thanks for the help! I rebuild my program using the files you have sent me, it worked fine 🙂

But I have just one question..when I set my sweep volatge from -0.0005 V to 0.0005 V across a resistor (22mOhm), it gives me a staircase like I-V curve. I am not sure why. Although it works fine when the voltage is from -0.005 to 0.005. 

Just shifing my one decimal point is causing the problem.

Any idea?

Thanks a lot once again!

Regards

Ainat

[CameronDean]

Hi ainat

This problem might be due to the way I was ramping the voltage. I was using the vi's to test very sensitive equipement so I ramped the voltage up in steps to avoid damaging HPDs. This was achieved by using loops. Maybe at lower voltages this ramping is noticable. Maybe try opening the Ramp vi's and getting rid of the loop? Sadly the rig with the 6487 is in use just now so I can't test this myself but hopefully this will fix your problem.

Regards
Cameron