User:Anthony Salvagno/Notebook/Research/2010/10/21/Tethering Re-Doing

Since I didn't get to finish what I was doing yesterday (lab) I will re-do the tethering experiments from yesterday. I also only used big beads, so today I will do the same experiments with small beads and big beads to compare effectiveness.

Tethering Z-Piezo
I didn't get around to tethering. Pranav and I started working with the z-piezo which is probably a good idea. We did some power spectrum using the z-piezo to position the focus precisely. Actually it worked well and we will need a program to be able to easily control the piezo. Right now we are using the NI Measurement and Automation package which allows you to test the device plugged in (I guess). We had to press update every time we changed voltage which was annoying, but it got the job done. We had really good stiffness for some reason today and we getting corner frequencies in the 600's (corresponding to ~80pN/W/100nm). I don't know what is up with that though.

The way we would measure the power spectrum was:
 * capture free bead
 * bring bead near surface (stuck beads would be in focus, in between white and black)
 * start at 0V for piezo
 * change V 100mV
 * measure power spectrum
 * change V again and measure power spectrum

So I think tomorrow we will do some DOG signal stuff with stuck beads and the piezo.

Also Pranav made a power supply from a computer power supply. I don't know if I'll ever need it, but he thought it would come in handy and I agree. Makes me wish I knew more about electronics, or really paid attention when I was in that awful class my junior year of undergrad.


 * Steve Koch 01:07, 22 October 2010 (EDT): I can probably quickly add a voltage control feature to the oscilloscope program so you don't have to click "update." A quick work-around, though, would be to run the feedback program on both computers.  Assuming you're running the z-piezo from Steveoffice.  You could then use the AOM control for the z-piezo.  That's a really big hack though, only worth it if it works right away.