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Strange Ripple when doing Pulse Mode Sweeps on 2430

Models 2400, 2401, 2410, 2420, 2425, 2430, 2440, 6430
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Wesdobson
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Joined: May 23rd, 2011, 12:57 pm
Country: United States

Strange Ripple when doing Pulse Mode Sweeps on 2430

Post by Wesdobson » May 23rd, 2011, 1:16 pm

Hi there.

I've got a 2430 sourcemeter which I'm using to do pulse mode IV sweeps on solar modules. I've done basic IV sweeps many times with your other source meters, but this is my first time messing around with pulse mode sweeps.

I'm getting a strange ripple on these sweeps whenever I sink current in the 3rd and 4th quadrants. I've attached a - to show what I'm seeing. In the -, the program I've written is inverting the current measurements, but these are all from the 4th quadrant. Depending on the settings I use, I start to get little ripples on the curve. The move around from test to test and aren't fixed to certain locations. At first I thought I was probably trying to do the measurement too quickly and getting noise, but what's strange is that if I make the measurement less marginal (increasing NPLC and the pulse and trigger delays), the ripple actually gets worse! The best setting I've found is just NPLC .1 and no delays with the longest possible pulse width. Sometimes I even get a little bit of ripple with that setting.

Am I doing something wrong or is this atypical behavior? Right now I'm skeptical that the values I'm seeing coming out of this thing is real because that ripple is such a variable.

In the photo, each example sweep is positioned next to the settings I used for that sweep. The same device was scanned in each case.

-Wes
Attachments
Weird Keithley 2430.png
Weird Keithley 2430.png (102.35 KiB) Viewed 15490 times

Wesdobson
Posts: 3
Joined: May 23rd, 2011, 12:57 pm
Country: United States

Re: Strange Ripple when doing Pulse Mode Sweeps on 2430

Post by Wesdobson » May 23rd, 2011, 4:12 pm

Here's a screenshot of my labview program which configures the sweep.

-Wes
Attachments
Setup.png
Setup.png (24.48 KiB) Viewed 15477 times

Dale C
Keithley Applications
Keithley Applications
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Joined: June 10th, 2010, 6:22 am
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Re: Strange Ripple when doing Pulse Mode Sweeps on 2430

Post by Dale C » May 24th, 2011, 11:05 am

Hello Wes,
Since you are trying to do "fast" pulsing and measuring I would not recommend using NPLC to reduce noise in Model 2430 pulse mode.
Try using the filter(:SENSE:AVER ON) and see if that helps with the noise.
Let me know what happens.

Wesdobson
Posts: 3
Joined: May 23rd, 2011, 12:57 pm
Country: United States

Re: Strange Ripple when doing Pulse Mode Sweeps on 2430

Post by Wesdobson » May 24th, 2011, 2:33 pm

Hey Dale,

I tried turning on filtering/averaging but got an error telling me "Error +831: Invalid in Pulse Mode." I looked at the manual and I guess filtering isn't allowed for pulse mode sweeps (section 5-12 page 120).

I'll try reducing the NPLC further. I didn't realize that an NPLC value of .1 is actually the maximum setting in pulse mode. On page 119 of the manual (at the bottom under measurement speed) it actually makes it sound like if I try to set the value higher than .1 then it will reset the value to .004, which is the lowest setting. Maybe that's why I was getting noise when I tired to set NPLC higher. Also, I guess in the 10A range, the maximum pulse width is 2.5ms and not 5ms, so even an NPLC value of .1 is really pushing it at that setting.

The manual also says something about not exceeding an 8% duty cycle in the 10A range for consistent pulse timing as well. I'll mess around with the pulse delay setting.

I'll let you know how it goes.

-Wes

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