Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
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design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
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Fast Frequency Measurement - RF Cafe Forums
RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media
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but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
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Post subject: Fast Frequency Measurement Posted: Sat May 20,
2006 12:47 am
Joined: Sat May 20, 2006 12:29
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!
Posted: Sat Jun 10, 2006 6:07 am
Fri May 19, 2006 5:01 am
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.
Posted: Mon Jun 12, 2006 8:43 am
Mon Jun 27, 2005 2:02 pm
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.