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Fast Frequency Measurement - RF Cafe Forums
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Tura
Post subject: Fast Frequency Measurement Posted: Sat May 20,
2006 12:47 am
Lieutenant
Joined: Sat May 20, 2006 12:29
am
Posts: 1
I need to track resonant frequency changes in a resonator.
The resonant frequency is about 230 kHz. I would like to measure resonant
frequency changes with noise level on the order of 1-5 mHz with a large
dynamic range, and I would like to sample this frequency at about 100
Hz or better.
I was wondering if a PLL could help me. Essentially,
I would like to take my signal (230kHz), convert it to a voltage proportional
to the resonant frequency, so that I can measure this output voltage
with a DAQ card. I'm not very competent when it comes to electronics,
so it would be great if someone could suggest circuits and components.
Thanks in advance!
Tura
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Charl
Post subject:
Posted: Sat Jun 10, 2006 6:07 am
Colonel
Joined:
Fri May 19, 2006 5:01 am
Posts: 25
Location: Netherlands
Hi
Tura,
Just a thought, might be silly.. you could heterodyne the
drifting 230KHz signal with a PLL'ed 230KHz (the calibration frequency
so to speak). If the frequencies differ, their difference frequencies
will be produced. This frequency should be so low that it's easily measurable.
Kind regards,
Charl
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IR
Post subject:
Posted: Mon Jun 12, 2006 8:43 am
Site Admin
Joined:
Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Hello,
What I woud suggest is simply to use an FM detector. The detector
provides a voltage relative to the frequency offset from the carrier
(The center frequency of 230kHz in your case). You can adjust the center
frequency by means of an inductor and capacitor (Variable). I worked
with such an IC 8 years ago in an FM receiver circuit. I am sure that
since then there are many new IC's availabel. Simply run a search in
Google I am sure you will get up on something.
Good luck!
_________________
Best regards,
- IR
Posted 11/12/2012
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