[time-nuts] Microphonic Inductor?

Bob Camp lists at rtty.us
Tue Apr 13 13:02:46 EDT 2010


Most inductors are vibration sensitive from the windings moving relative to
the core. If the part in question has windings you can get at - try gluing
them down. Anything with some mass to it will do fine (RTV, hot melt glue,
wax, what ever). The value will change, but if the vibe problem goes away
you have useful data.


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of SAIDJACK at aol.com
Sent: Tuesday, April 13, 2010 12:49 PM
To: time-nuts at febo.com
Subject: Re: [time-nuts] Microphonic Inductor?

Hi there,
I do have space on the PCB, but I am worried that the ceramic as well as  
ferrite cores both are sensitive to vibration.
I will try Joe's idea of using a doorbell buzzer to introduce vibration.  
It's not easy to generate 1KHz vibration without professional (and heavy)  
equipment :)
Another suggestion was to put the part on a scope, and lightly tap it, to  
see any variations in voltage.
It's time to experiment.
If anyone knows a good inductor-series (leaded or smt) that is  
known-insensitive to vibration please let us know!
In a message dated 4/13/2010 06:34:53 Pacific Daylight Time,  
wpxs472 at gmail.com writes:

I assume you are using something like the Coilcraft 0603 LS  series which
seem to have ferrite cores. You might want to try a 0805 size  part since
that inductance is available in the CS series which are ceramic  only. I
don't know if size constraints prohibit using an 0805 but you can  try one 
see if the inductor is the problem.If you must use a 0603, you  might try
massaging the filter impedance so you can use a 390 nH which is  available 
0603 size with a ceramic core. Then, you will either have to  put up with a
mismatch or include some impedance matching components. I use  the LS series
0603s a lot and they are somewhat temperature sensitive if  that could be an
issue. The ceramic cored CS series don't seem to be  temperature sensitive.
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