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# Understanding raw data in header of force curve files

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4 Posts
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Josep Relat posted on Fri, Jan 27 2012 8:23 AM

I am programming some code to export (point and shot) force curves to Igor pro. I have almost finished but there is a problem: I measure both deflection and height sensor for the curves, but it is impossible to get a proper scale for height sensor. Currently I am using the parameters

\@Sens. ZsensSens:   nm/V

\@4:Z scale: V [Sens. ZsensSens] (...)  V (the hard value, not the scale)

in order to obtain the height at each point. Could anyone tell me which are the correct values and if any other parameter is needed? Of course, I could just get de Z scale and divide it by the number of points in the curve. However, I would like to have a good measure of Z. Is there any  difference between obtaining the Z piezo by the Z scale or by measuring it with the height sensor?

PD: I use a Dimension Icon with 8.1 software (if I am not wrong)

Thank you,

Josep

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280 Posts
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Bede Pittenger replied on Fri, Jan 27 2012 1:47 PM
Suggested by Bede Pittenger

Hi Josep,

You are on the right track.  The scaling factor is just the product of the ZsensSens and the Zscale value in parenthesis.  For example

\@Sens. ZsensSens: V 163.0064 nm/V

...

\@4:Z scale: V [Sens. ZsensSens] (0.0003750000 V/LSB) 5.966755 V

...

the scaling factor for the Height Sensor channel  would be 163.0064*0.000375 nm/LSB.  To read the data use something like this:

where the S option and U option come from the header:

\*Ciao force image list
\Data offset: 40960
\Data length: 8192 (this is twice the number of data points)

and the W option is the number of data channels in the file.

Good luck!

--Bede

4 Posts
Points 52
Josep Relat replied on Sat, Jan 28 2012 11:16 AM

Thank you very much for the explanation. However, there is one thing I don´t understand. In some part of appendix 1 in the software manual it is said that the hard scale (0.0003750000 V/LSB in the example) is not as precise as the hard value (5.966755 V in the example). Is this true? If this is the case, how could I calculate the hard scale from the voltage value? I read that the conversion is (hard value)/65536*(Full voltage range), where Full Volatge range is 5,10 or 20 depending on the mode. However, it didn´t worked.

Thanks,

Josep

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280 Posts
Points 6,221
Bede Pittenger replied on Tue, Jan 31 2012 8:24 PM

It appears that the manual is incorrect in this case.  I would recommend using the "Hard Scale".

Can you tell me the version of the manual?  That you are using?  I'll check it out...

--Bede

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10 Posts
Points 120
Jonathan replied on Mon, Feb 13 2012 10:45 AM

Hi Josep,

I did some programming too, see here http://nanoscaleworld.bruker-axs.com/nanoscaleworld/forums/p/809/2582.aspx#2582

My python script did for me the Igor Export, but I hard coded the important things. If you are interested we might exchange our experiences. There seems to be a major interest in this kind of software.

Greetings

Jonathan

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