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Audio amplified VSM (vibrating sample magnetometer) sample

  1. May 10, 2015 #1
    I am trying to get the induced emf reading from a sample in a vsm. A lock in amplifier is being used to read the signal. The problem is that the output voltage fluctuates heavily. Should I apply an audio amplified signal to my sample to make it vibrate ?
  2. jcsd
  3. May 15, 2015 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
  4. May 21, 2015 #3


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    Sorry about the delay in reply.

    My suspicion is that there is a fault in the VSM. There are many possible causes of a fluctuating signal from a Lock In Amp, LIA.
    Loss of signal input, reference input or some external interference are all possible causes.

    I would expect the sample to vibrate sinusoidally. Is it moving? If not, why not?

    The position sensing transducer may be faulty or have a broken cable. Use an oscilloscope to check the reference signal into the lock in amp. Is it there?

    The pickup coils may have a faulty connection. Measure resistance of the coils while disconnected from LIA inputs.They should be similar low ohms.

    The LIA may have a faulty power supply. Connect the known good reference signal to both the reference input and the signal input. Is it now stable?

    If the problem is not resolved please post your instrument's Make and Model information.
  5. Jun 13, 2015 #4
    I am working also on building a VSM and I'm a little lost as to how to collect the data. From what I see on other papers and thesis their LIA output always comes out as a positive value, but I get values that fluctuate from positive to negative very near the frequency of oscillation of my sample. I am not sure if I am doing anything wrong or if that's how it's supposed to come out. I haven't been able to figure it out yet.
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