Accelerometers for >1000g measurements

[Phil Hobbs]

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

[john larkin]

On Wed, 4 Sep 2024 18:30:46 -0400, Phil Hobbs

Post by Phil Hobbs
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?

[Jan Panteltje]

On a sunny day (Wed, 04 Sep 2024 19:57:04 -0700) it happened john larkin

Post by john larkin
On Wed, 4 Sep 2024 18:30:46 -0400, Phil Hobbs

Post by Phil Hobbs
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...
?

[John R Walliker]

Post by Jan Panteltje
On a sunny day (Wed, 04 Sep 2024 19:57:04 -0700) it happened john larkin

Post by john larkin
On Wed, 4 Sep 2024 18:30:46 -0400, Phil Hobbs

Post by Phil Hobbs
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

[Phil Hobbs]

Post by John R Walliker

Post by Jan Panteltje
On a sunny day (Wed, 04 Sep 2024 19:57:04 -0700) it happened john larkin
<jlarkin_highland_tech> wrote in

Post by john larkin
On Wed, 4 Sep 2024 18:30:46 -0400, Phil Hobbs

Post by Phil Hobbs
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

[john larkin]

Post by Jan Panteltje
On a sunny day (Wed, 04 Sep 2024 19:57:04 -0700) it happened john larkin

Post by john larkin
On Wed, 4 Sep 2024 18:30:46 -0400, Phil Hobbs

Post by Phil Hobbs
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.

[John R Walliker]

Post by john larkin

Post by Jan Panteltje
On a sunny day (Wed, 04 Sep 2024 19:57:04 -0700) it happened john larkin

Post by john larkin
On Wed, 4 Sep 2024 18:30:46 -0400, Phil Hobbs

Post by Phil Hobbs
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

[Glen Walpert]

Post by john larkin

Post by Jan Panteltje
On a sunny day (Wed, 04 Sep 2024 19:57:04 -0700) it happened john larkin
<jlarkin_highland_tech> wrote in

Post by john larkin
On Wed, 4 Sep 2024 18:30:46 -0400, Phil Hobbs

Post by Phil Hobbs
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

[Phil Hobbs]

Post by Glen Walpert

Post by john larkin

Post by Jan Panteltje
On a sunny day (Wed, 04 Sep 2024 19:57:04 -0700) it happened john larkin
<jlarkin_highland_tech> wrote in

Post by john larkin
On Wed, 4 Sep 2024 18:30:46 -0400, Phil Hobbs

Post by Phil Hobbs
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
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

[john larkin]

On Thu, 5 Sep 2024 12:09:36 -0400, Phil Hobbs

Post by Phil Hobbs

Post by Glen Walpert

Post by john larkin

Post by Jan Panteltje
On a sunny day (Wed, 04 Sep 2024 19:57:04 -0700) it happened john larkin
<jlarkin_highland_tech> wrote in

Post by john larkin
On Wed, 4 Sep 2024 18:30:46 -0400, Phil Hobbs

Post by Phil Hobbs
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
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.

[Bill Sloman]

Post by Phil Hobbs
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.

[Arie de Muijnck]

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

[Phil Hobbs]

Post by Arie de Muijnck

Post by Phil Hobbs
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