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Bad Triggering in high-speed data capturing

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Polis Tyrol posted on Thu, Aug 29 2013 4:51 AM

Dear community,

I have an issue regarding my force-distance curves. I produce Peak-Force QNM image that are nice (as I think) and I can create good force-distance curves using the Point-&-Shoot option. However, using the High-Speed Data Cature (HSDC) option or the Peak Force Capture (PFC) option, I fail miserably. The reason seems to be bad triggering - while the deflection-over-time plot looks nice, the deflection-over-distance curve does not. One can see that the system triggered at a snap-up rather than at maximum force:

I tried it several times at different positions, but I couldn't fix it. I use a MultiMode 8 and scan 512 px at nearly 1 Hz. The sample has a surface roughness of about 4 nm.

How can I avoid this effect if I have to face it? Is it possible to fix that problem with data analysis?

Thanks, Dietmar

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Peak Force Capture provides full access to force curves for analysis  and its the best techniques for measuring the high speed data capturing like high-resolution property mapping on biological samples with corresponding high-resolution topography.

Any one using Quantitative Force-Volume Mapping.

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Bruker Employee

Hi Dietmar,

Are most of the curves in the HSDC capture like this?  Or is this an unusual curve?  

If you look at the force vs. Z plot in the force monitor (in realtime) do you see the same behavior?  Or do they look correct in realtime?  

What version of Nanoscope and Nanoscope analysis are you using?

--Bede

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Dear Bede,

On that day every HSDC or PFC curve looked like that. It was just the Point-&-Shoot curves that were fine. However, the real time force curve looked okay - it was just sometimes very wavy, going up and down all the time. I clicked "AutoConfig" several times to get rid of that behavior, but it didn't help.

I use NanoScope Analysis 1.40 R3Sr4. I'll check the version of the Nanoscope software as soon as possible.

Best regards, Dietmar

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The NanoScope version I use is 8.15 (Build R3Sr4).

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Polis Tyrol replied on Tue, Sep 10 2013 1:53 AM

Dear all,

I figured out how to avoid the issue. It had to do with the fact that I set the Gain manually after calibration: In order to keep the imaging settings the same I fixed the Gain at one value the same way as I did it for the Peak Force Setpoint and other values. Although my Gain was normally as high as 50 this was obviously still to low for my very rough samples. After setting the Gain to 70 the images became much better, as well as the force curves.

From now on I will stop to keep the Gain setting constant. I will rather adjust it depending on the roughness of the sample and the Scan Size.

Best regards, Dietmar

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Bede Pittenger replied on Tue, Sep 10 2013 3:47 PM

Glad to hear that you figured it out.

It is important that the gain is not too small or too large -- you will see the curves jumping and big variations in the peak force error if the gain is too large as well...

--Bede

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Polis Tyrol replied on Mon, Sep 23 2013 6:02 AM

Dear all,

I am sorry that I need to re-open this issue. Unfortunately the gains were not the explanation for the bad triggering. It happens sometimes also with automatic gains, and varying the gains manually doesn't help. If it happens, all the HSDC curves look like that. I found that if I do not Auto Config after Engaging the live force curves looks like that as well. Just after the first AutoConfig it improves.

Is there a way to alter the trigger properties during operation?

Thanks a lot, Dietmar

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I don't know if you solved this issue or not, but if you did, what's your advice? Also what kind of software did you use for analysis?

 

Thanks, 

Stav

Polis Tyrol:

Dear all,

I am sorry that I need to re-open this issue. Unfortunately the gains were not the explanation for the bad triggering. It happens sometimes also with automatic gains, and varying the gains manually doesn't help. If it happens, all the HSDC curves look like that. I found that if I do not Auto Config after Engaging the live force curves looks like that as well. Just after the first AutoConfig it improves.

Is there a way to alter the trigger properties during operation?

Thanks a lot, Dietmar

 

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