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From: John R Walliker <jrwalliker@gmail.com>
Newsgroups: sci.electronics.design
Subject: Re: Accelerometers for >1000g measurements
Date: Thu, 5 Sep 2024 15:59:26 +0100
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On 05/09/2024 15:07, john larkin wrote:
> On Thu, 05 Sep 2024 06:22:04 GMT, Jan Panteltje <alien@comet.invalid>
> wrote:
> 
>> On a sunny day (Wed, 04 Sep 2024 19:57:04 -0700) it happened john larkin
>> <jlarkin_highland_tech> wrote in <md7idj1plqodnthuqpcemaphbrtotlqveh@4ax.com>:
>>
>>> On Wed, 4 Sep 2024 18:30:46 -0400, Phil Hobbs
>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>
>>>> So for this customer gig I need to measure the actual acceleration of a
>>>> parallel-rod transmission line that's being pounded into the ground with
>>>> a built-in slide hammer.  (It's for measuring soil moisture and salinity
>>>> by TDR.)
>>>>
>>>> We're thinking about putting the TDR pulser and sampler in the part that
>>>> gets pounded (in a potted module obviously), so knowing how bad the
>>>> acceleration gets is going to be important.  I expect that it'll be
>>>> several hundred g in volcanic soil, so a full-scale range of 1000-2000 g
>>>> would be about right.
>>>>
>>>> None of the MEMS IC accelerometers go anywhere near that high.
>>>> Measurement Specialties makes them, but they're $160 in onesies, e.g.
>>
>>
>> If you can make it emit some ultrasonic sound you can measure the received frequency shift from far away?
>> Same for RF likely...
>> ?
> 
> No, just measure the voltage or the charge that it generates under
> acceleration. It's a polarized, piezoelectric ceramic thing for 30
> cents.
> 
> https://www.mouser.com/c/?q=ceramic%20resonator
> 
> One might also measure its resonant frequency vs acceleration.
> 
> I wonder how one would test it. At 2000 g's.
> 
> Even ceramic caps are notoriously microphonic. Maybe just look at your
> own power supply rail.
> 
> The guys who make expensive crystal oscillators go to great lengths to
> make them G-insensitive. I suspect that the folks who make cheap
> oscillators don't.
> 
> You could lay out a strain gauge on the PCB too.
> 
> During WWII, we fired proximity fuze shells out of rifled cannons at
> 20,000 Gs and 20,000 RPM. With tubes.
> 
They were very special small tubes and the whole circuit was 
encapsulated in wax.

John