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Entry  Sun Jan 10 13:32:09 2010, Haixing, Update, SUS, transfer function measurement of the quadrant maglev circuit  6x
    Reply  Sun Jan 10 15:47:26 2010, Koji, Update, SUS, transfer function measurement of the quadrant maglev circuit  
       Reply  Sun Jan 10 16:50:34 2010, Haixing, Update, SUS, transfer function measurement of the quadrant maglev circuit  
          Reply  Sun Jan 10 17:15:25 2010, Koji, Update, SUS, transfer function measurement of the quadrant maglev circuit  
Message ID: 2494     Entry time: Sun Jan 10 13:32:09 2010     Reply to this: 2495
Author: Haixing 
Type: Update 
Category: SUS 
Subject: transfer function measurement of the quadrant maglev circuit  

I have assembled the circuit and the control box for the quadrant magnetic levitation yesterday. The final setup is shown

in the figure below:

Quad_maglev_ctrl_box_in.JPGQuad_maglev_ctrl_box_front.JPG

 

Due to my carelessness, I I connected the wrong ends of the power supply. I damaged 4 op-amp and one voltage 

regulator during this assembly. This stupid mistake spent me several hours to fix, and I got a bitter lesson;-(

 

Afterwards, I replaced those op-amps and reconnected the power supply . Kiwamu helped me and we measured

the transfer function of this circuit.  The transfer function agrees with  the specification in the schematics which

has a integrator below 1 Hz and a differentiator from 5 to 20 Hz. The bode plot for the measured transfer function

is the following:

quad_mag_tf_amp.png

 quad_mag_tf_phs.png

Today I tested the photodetector parts and found that there is a mysterious oscillation. Whenever I connect the

photodector input A of the circuit (as indicated in the figure below),

PD.PNG

the output of the op-amp has a 500k Hz oscillation shown up in the oscilloscope.This happens even A is disconnected from

the photodetector and connected to an open end wire. I don't know how to eliminate it, and its amplitude is so large (peak to

peak is around 2.5 V) which completely dominates the photodetector output. Does anybody has some ideas? Thanks.

 

Quad_mag_lev_osc.JPG

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