• Accelerometers for >1000g measurements

    From Phil Hobbs@21:1/5 to All on Wed Sep 4 18:30:46 2024
    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.

    <https://www.digikey.com/en/products/detail/te-connectivity-measurement-specialties/830M1-2000/14118098>

    Anybody used them?

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

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  • From john larkin @21:1/5 to pcdhSpamMeSenseless@electrooptical. on Wed Sep 4 19:57:04 2024
    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.

    <https://www.digikey.com/en/products/detail/te-connectivity-measurement-specialties/830M1-2000/14118098>

    Anybody used them?

    Cheers

    Phil Hobbs

    Ceramic resonator maybe?

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  • From Bill Sloman@21:1/5 to Phil Hobbs on Thu Sep 5 15:46:35 2024
    On 5/09/2024 8:30 am, Phil Hobbs 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.

    <https://www.digikey.com/en/products/detail/te-connectivity-measurement-specialties/830M1-2000/14118098>

    Anybody used them?

    No. But there's a new kid on the accelerometer block.

    https://singularityhub.com/2022/10/31/new-3d-quantum-accelerometer-leaves-classical-sensors-in-the-dust/

    A recent edition of Review of Scientific Instruments had a bunch of
    papers on the subject. On the face of it a laser-cooled cloud of
    rubidium atoms in a vacuum under a corner cube reflector isn't something
    that you would want to put inside a pile driver, but apparently the
    actually measuring head is quite small.

    The proximity fuse is a famous example of something ostensibly fragile
    that could be re-engineered to survive being fired out a gun.

    I actually met - and worked for - William S. Butement, who had the
    original idea for that, probably because he didn't have enough sense to
    realise how impractical it was.

    --
    Bill Sloman, Sydney

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  • From Jan Panteltje@21:1/5 to All on Thu Sep 5 06:22:04 2024
    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...
    ?

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  • From john larkin @21:1/5 to All on Thu Sep 5 07:07:25 2024
    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.

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  • From Phil Hobbs@21:1/5 to John R Walliker on Thu Sep 5 10:28:02 2024
    On 2024-09-05 06:02, John R Walliker wrote:
    On 05/09/2024 07:22, Jan Panteltje 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...

    Attach an adhesive label printed with a black and white wedge to
    the rod.  Illuminate with uniform light and view with a photodiode
    lens slit combination.  Capture the velocity waveform on 'scope.
    Calibrate at low speed.
    I expect the acceleration peak might only last a few microseconds
    but could be many thousands of g.

    John


    It's not that hard to estimate. The hammer part is about 130 mm tall,
    and the speed of a compressive wave in steel is 6 km/s or so. Thus the
    impulse will last at least 22 us. If the hammer and the electronics
    assembly have about the same mass, and everything is perfectly elastic,
    in the collision the hammer will go from speed v to zero, and the
    electronics will go from zero to v (the same speed as the hammer).

    If the hammer speed is 10 m/s at impact (probably an overestimate), the acceleration will be about

    10 m/s / 22 us = 450 000 m/s**2, or about 45000 g, quoted to about two
    more significant figures than I'm entitled to.

    In real life the hammer won't be that fast, but the electronics assembly
    is heavier than the hammer and won't react as a unit. It'll be that
    order of magnitude in the limit of very stiff material. A compliant
    layer would reduce that, and so will the right choice of potting
    material, but the effects on the cables have to be considered.

    Anecdotally it can take as much as 150 hammer blows to get the 60 mm
    tines fully inserted in the soil, so we're going to need this gizmo to
    survive at least 1E6 impulses over a 10-year life.

    And then there's the ferrite-loaded shotgun balun to go from coax to the balanced line. ;)

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

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  • From Glen Walpert@21:1/5 to john larkin on Thu Sep 5 15:10:34 2024
    On Thu, 05 Sep 2024 07:07:25 -0700, 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.

    Compare to a single expensive calibrated accelerometer? Not familiar with Measurement Specialties, other possibilities are:

    https://www.kistler.com/INT/en/c/accelerometers/CG21-accelerometers https://buy.endevco.com/accelerometer

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  • From Phil Hobbs@21:1/5 to Glen Walpert on Thu Sep 5 12:09:36 2024
    On 2024-09-05 11:10, Glen Walpert wrote:
    On Thu, 05 Sep 2024 07:07:25 -0700, 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.

    Compare to a single expensive calibrated accelerometer? Not familiar with Measurement Specialties, other possibilities are:

    https://www.kistler.com/INT/en/c/accelerometers/CG21-accelerometers https://buy.endevco.com/accelerometer

    Thanks, Glen, good leads.

    The PCB Piezotronics folks (formerly Endevco) have the single-axis,
    +-50k gees model 350D2 for $1200ish in onesies, which we may wind up buying.

    Cheers

    Phil

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

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  • From Arie de Muijnck@21:1/5 to Phil Hobbs on Thu Sep 5 17:35:32 2024
    On 2024-09-05 00:30, Phil Hobbs 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.

    <https://www.digikey.com/en/products/detail/te-connectivity-measurement-specialties/830M1-2000/14118098>

    Anybody used them?

    Cheers

    Phil Hobbs


    I've measured big fast forces using strain gauges.
    If you can be sure the place where you place that on the metal rod stays elastic during the acceleration the bandwidth should not be a problem.
    Now, computing a calibration and amplifying that signal is the next problem...

    Arie

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  • From Phil Hobbs@21:1/5 to Arie de Muijnck on Thu Sep 5 12:49:40 2024
    On 2024-09-05 11:35, Arie de Muijnck wrote:
    On 2024-09-05 00:30, Phil Hobbs 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.

    <https://www.digikey.com/en/products/detail/te-connectivity-measurement-specialties/830M1-2000/14118098>


    Anybody used them?


    I've measured big fast forces using strain gauges.
    If you can be sure the place where you place that on the metal rod stays elastic during the acceleration the bandwidth should not be a problem.
    Now, computing a calibration and amplifying that signal is the next problem...

    Thanks. The issue there would be calibration, as you say, as well as
    the fact that it would measure the stretch at the surface and not the
    actual acceleration.

    The objects in question don't have simple shapes, so going from the one
    to the other is a bit of a science project in itself.

    If I can buy one with a cal sheet, that'll save me a lot of time.

    Glen's other lead, Kunstler, advertises the model 8742A-50, also +-50k
    gees. I have a quote request out to them too.

    Next question is how to make SMT PCB survive a million cycles of that.
    Those fuze guys had it easy. ;)


    Cheers

    Phil Hobbs


    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

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  • From john larkin @21:1/5 to pcdhSpamMeSenseless@electrooptical. on Thu Sep 5 20:55:32 2024
    On Thu, 5 Sep 2024 12:09:36 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    On 2024-09-05 11:10, Glen Walpert wrote:
    On Thu, 05 Sep 2024 07:07:25 -0700, 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.

    Compare to a single expensive calibrated accelerometer? Not familiar with >> Measurement Specialties, other possibilities are:

    https://www.kistler.com/INT/en/c/accelerometers/CG21-accelerometers
    https://buy.endevco.com/accelerometer

    Thanks, Glen, good leads.

    The PCB Piezotronics folks (formerly Endevco) have the single-axis,
    +-50k gees model 350D2 for $1200ish in onesies, which we may wind up buying.

    Cheers

    Phil

    Do you only need one. or do you want to put one into every probe?

    If it's one, buy something expensive and calibrated.

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