主题：[讨论]关于setpoint，怎么理解

同问啊，
只被人指教说下针尖后，要稍微调小这个值，还真不清楚啊，
高手出来说说，我仅能做tapping

我也想知道啊，有没有高手指教下啊

Set point is just a non physical meaning word. You can see there are a lot of set point value for AFM. Set point are used for different way. From word meaning, Set point mean 設定值. They are used for feedback control. For constant set point operation, During AFM scanning, tip deflection or amplitude change out of set point, the Z piezo will change position to make make system back to set point value. The Z change position is our surface height data. For constnat height operation, Z piezo does not move, so we get tip delflection or amplitude change data.

Different companies and AFM mode define set point differently.

Why we need to adjust sep point a little lower ?

For Tapping mode, there are 2 set point value.

(1) Set point : You can think it is hight adjustment (not really, there is a complex formular from manual. During engae, the system maker define set point valur from your initial scan parameters to make sure tip not tapping surface to hard to broken tip or surface. The engage will automatic stop to let tip height and amplitude combination just light tapping surface. Someone call this this false engae. During this stage, tip just touch surface very light. Maybe not touch the bottom of suface feature. If there is a fluid layer above surface, you will see feedback is not stable and can not see sharp image. For good feedback, we need to let tip touch all of surface. So adjust a smaller set point can let tip close to surface and really touch surface. You also can increase Amplitude set point to get same purpose.

(2)Amplitude set point : This is to define amplitude of tip vibration. You also can increase Amplitude set point to get same purpose.

http://www.tbcl.com.tw/Product/SPM/SPM.htm has drive oscillation simuator to help you to know this relationship.

原文由 hitttr 发表:
在AFM的的接触模式和轻敲模式中都有setpoint,
接触模式中的setpoint比较好理解，
可以认为是设定的针尖和样品间相互作用力的大小，
（在电路中表现为光斑在PSD中移动的大小）
然后用当前PSD中所取得的值与其进行比较，然后反馈。
但在轻敲模式中，个人感觉SetPoint理解起来要比接触模式的要困难些。
希望达人解惑！

PSD 是什麽的缩写啊？

位置敏感探测器:position sensitive detector
有时候也说是 position-sensitive photo-detector (PSPD).

原文由 cyanapple 发表:
PSD 是什麽的缩写啊？

这个Amplitude set point 似乎很少去管它啊，谁给详细讲讲？

原文由 hansentbcl 发表:

Set point is just a non physical meaning word. You can see there are a lot of set point value for AFM. Set point are used for different way. From word meaning, Set point mean 設定值. They are used for feedback control. For constant set point operation, During AFM scanning, tip deflection or amplitude change out of set point, the Z piezo will change position to make make system back to set point value. The Z change position is our surface height data. For constnat height operation, Z piezo does not move, so we get tip delflection or amplitude change data.

Different companies and AFM mode define set point differently.

Why we need to adjust sep point a little lower ?

For Tapping mode, there are 2 set point value.

(1) Set point : You can think it is hight adjustment (not really, there is a complex formular from manual. During engae, the system maker define set point valur from your initial scan parameters to make sure tip not tapping surface to hard to broken tip or surface. The engage will automatic stop to let tip height and amplitude combination just light tapping surface. Someone call this this false engae. During this stage, tip just touch surface very light. Maybe not touch the bottom of suface feature. If there is a fluid layer above surface, you will see feedback is not stable and can not see sharp image. For good feedback, we need to let tip touch all of surface. So adjust a smaller set point can let tip close to surface and really touch surface. You also can increase Amplitude set point to get same purpose.

(2)Amplitude set point : This is to define amplitude of tip vibration. You also can increase Amplitude set point to get same purpose.

http://www.tbcl.com.tw/Product/SPM/SPM.htm has drive oscillation simuator to help you to know this relationship.

Amplitude set point : This is to define amplitude of tip vibration.
我的理解是设置TIP振动的偏压，调整TAPPING时的振幅。
不同TIP，设置的数值不定，一般调整到合适的数值就不用管它，如何算调整好，各个厂家都有相应不同的说明吧（估计，没用过多少AFM）。
如果是做变温的话，随着温度的升高，TIP的性质有较大改变，如共振频率，振幅，这时就要调整Amplitude set point至合适值。

没怎么接触AFM，欢迎指正，不胜感激！