Current Measurement using Keithly 6485

[YogeshL]

Hi, I'm trying to measure current using a Keithley 6485 Picoammeter. I've developed a LabVIEW VI code, which I'm attaching. The code is communicating with the 6485, but the measurements are in the range of 10^(-14). Could someone please help me figure out if I'm missing something?

[altenbach]

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@YogeshL wrote:

I've developed a LabVIEW VI code, which I'm attaching.

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Unfortunately, you only attach a picture (not code!) which is insufficient for troubleshooting. We can't even tell the values of any of the controls.

What determines the loop rate? Do you get any errors?

[YogeshL]

Hi, Thank you for the reply. I will attach the code with you now and I didn't get any error while running it, just that I didn't get the expected current measurement.
Example scenario :- I have set 2ma but this was reading 9 *10^(-14) A.

[YogeshL]

Also Note this the how the front panel looks, and I usually use the default values. So I will enter only Visa Code, is that the reason of incorrect outputs?

 

[YogeshL]

Can someone please help? or if possible, can someone share their working VI which can measure current?

[NIquist]

The shipping examples will be the best working VIs to start with.  If you've installed the 6485 drivers, they should be in your palette.

If not, your first step is to install them:  Keithley 648X Series Meter - IEEE 488.2 (GPIB), Serial Driver for LabVIEW - National Instruments

[YogeshL]

That step is done, Matter of fact when trying debugging noticed that my VI is communicating with 6485. But the problem is the reading are way off range.
Also, I have tried those examples but those seems to be not useful for me.

[NIquist]

I don't have that meter, but I did see a VI in the package called Measure Current.vi.   It's in Data palette and if nothing else you can copy the string it sends and use that in NI-MAX.

This should be very easy if you're using GPIB VISA.  If you're using a serial connection, you might have the parameters set inconsistently.  You need to check your meter and match the serial parameters in your code.

Also, I know it's obvious, but are you SURE you have a proper current load connected?  Could you be set for rear panel inputs??  Blown current protection fuse???

[YogeshL]

The VI that you mentioned is the VI that I used in the code I shared, I think there must be some Configuration done before measuring current and that's where I feel I am making mistakes.

Also, the Load is connected properly and when I try to manually measure current using 6485, its working fine.

[NIquist]

Hmmm, if you can get a good reading manually, that simple VI should work.  Normally the default settings will give you a good start.  They are generally set to AUTO everything so it's easy to get started.

Are you using Serial or GPIB?  This is starting to sound like a serial port configuration issue.