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Ramp rate versus force control...

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BenSD posted on Fri, Apr 19 2013 12:34 PM

Hello,

I am doing an experiment in ramp mode where I need to use a wide range of ramp rate (from 2 to 20Hz).
I am doing single force curve at constant force and various ramp rate. However when I increase the ramp rate the force applied increase. For instance with a trigger threshold of 8µN, at 2Hz the force go up to 8.5µN but at 20Hz the force go up to 12µN. It seems that the feedback loop is not fast enough at high ramp rate.

Another question is about the ramp rate value. I can't fix any values between 13 and 19.5Hz, when I enter 15Hz it put automatically 19.5Hz. Why is that?

Thank you very much!

Benoit.

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Ang Li replied on Tue, Apr 23 2013 9:27 AM

Hi, The scanner won't stop immediately when trigger force is reached since it's linear ramp mode and it takes time from constant velocity to zero. The higher frequency, the higher speed and more overshoot in terms of force. 

The frequency is linked to ramp size, you just try a slightly different ramp size.

Ang Li

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