40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  SUS Lab eLog  Not logged in ELOG logo
Message ID: 652     Entry time: Fri Jun 28 00:30:46 2013
Author: Giorgos 
Type: DailyProgress 
Category: SUS 
Subject: Hall-effect sensors circuits 

Today, we analyzed the transfer function of our circuit:

High-pass_filter.png

 Specifically, Vout/Vin= -((R_1 〖+R〗_2)R_3)/(R_1 R_2 ) {((s+Z_o)P_1)/((s+P_o)(s+P_1))} where Z0, P0, and Pare important parameteres of our transfer function.

Were we to graph it against frequency:Transfer_function_of_Hall-effect_sensors_circuits.png

So, we determined the values of R1, R2, R3, C1, and C2 so that Zo occurs at 0.1Hz (close to the estimated natural frequency of the levitated plate), Po=50Hz and P1=200Hz Specifically, R1=R313kΩ, R2=1.5kΩ, C1=2.2μF, and C2=61nF. We did not have a 61nF capacitor, so instead we used a 47nF one (slightly changing our P1 point).

Our Hall-effect sensors give a constant 2.5V when no magnetic field is present. Therefore, we need to include an offset of 2.5V. We will achieve that with a voltage divider with R1=13kΩ, R2=4.3kΩ, R3=R4=2.2kΩ.

In the afternoon, I wired up 7 PCB boards for the Hall-effect sensors circuits. These include the -2.5 offset and the high-pass filter. We used the spectrum analyser to see whether the transfer function of our circuits are as predicted; the experimental and theoretical data agreed.

ELOG V3.1.3-