[time-nuts] Sound impact Was FEI-5660 Rubidium Oscillator
robert8rpi at yahoo.co.uk
Fri Mar 28 08:32:47 EDT 2014
Back in 1997 when working on a car project I saw several failures of AD595 Thermocouple converter chips due to sound. In all cases the bond wire to pin 8 of the CERDIP package failed, presumably due to resonance (I took the top of the chips to check) A blob of non acid cure RTV silicone rubber on the chip seemed to cure it. The box with the AD595s was mounted in the rear of the car between the exhaust plumes of two 20,000lb thrust re-heated jet engines so the sound level was quite high :-) The box is in the open wheel compartment seen here http://upload.wikimedia.org/wikipedia/commons/4/41/ThrustSSC_back.jpg
From: Bob Camp <lists at rtty.us>
To: Tom Van Baak <tvb at leapsecond.com>; Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Friday, 28 March 2014, 11:33
Subject: Re: [time-nuts] FEI-5660 Rubidium Oscillator
Crystals are susceptible to vibration. That’s pretty well documented. They have resonances in the mount structure. They have a 2G tip sensitivity.
Audio when it “impacts” an oscillator induces vibration. If your noise source is a rocket engine, then the vibration is “non trivial”. You do indeed see phase noise on the oscillator from audio …
On Mar 27, 2014, at 11:42 PM, Tom Van Baak <tvb at LeapSecond.com> wrote:
>> More seriously, I'm assuming you're advocating rock for the thermal mass
>> and/or mechanical. What about a 100 pound box of sand?
> Mechanical. I figured a OCXO might be susceptible to microphonics, especially in a recording studio. But if it's down to the level of 1 lsb of the digital sampling, then no worries.
> Has anyone on the list ever measured this effect, even on a cheap crystal?
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