shock detection

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How bout springs? F = kx, mount two opposite springs(actually 6) on a ball
then any accelleration will compress one and extent the other... the amount
of acceleration being proportional to the acceleration... i.e., F = ma = kx.
(with 3 axis you'll need a better algorith as it would depend on the
orientation(in this case it does too but I'm assuming lateral motion)).

What? Something that can detect free-fall without external
measurement?

But seriously, I don't see what real damage could come from a handheld made
of solid gold. What if it is dropped? Why does it matter? Does the gold
really know its in free fall?

Just because you never worked with anything worth over 5$ doesn't mean
it can't exist. Stop being so snide.

 

[Ecnerwal]

I need to find a way to detect whether our hand held instrument ($25k-
$40k) was abused (dropped, bumped, etc).

On further consideration, if I spent $25-40K on something "handheld",
I'd expect the maker to have bothered to engineer it to take the normal
things that can be expected to happen to a hand-held item, such as being
dropped 3-8 ft onto a concrete or steel surface (in any orientation),
without blinking, much less breaking. If it can't even be "bumped",
you'd better sell it as a suitcase-sized item, with the package you have
now sitting in the middle of a lot of soft foam, surrounded by a hard
shell.

 

[Tim Williams]

But seriously, I don't see what real damage could come from a handheld made
of solid gold. What if it is dropped? Why does it matter? Does the gold
really know its in free fall?

No, the gold does not. However, the owner of the toe beneath it does.

Tales of Fort Knox eh...

On topic: there are clear bouncy ball things with an LED flasher inside. A
spring, clearly visible, bounces against a pin. A couple second one-shot
is activated that runs the flasher.

(Hmm, I wonder how they get the battery inside there. Rubber isn't cooked
at a very cold temperature. Must be a different elastomer.)

Any solenoidal spring always flexes easier in bending than in compression,
and any axial force will soon end up converted to torsion and bending due
to the spring's coiled geometry. Only one spring is necessary, but good
luck calibrating it. It'll also have a resonant peaked response unless you
immerse it in glycerin.

Tim

 

[Nobody]

We need to have a time stamp (to be able to properly assign
blame ;o) ) - glass tubes won't do.
I do not know:
a. "how much is too much?"
b. How to keep this system running for, say, two months between
recharges on whatever tiny volume available for the battery. The
minimum I will need (I have found so far is) ~1..1.5Amp-hour cell.
It's not tiny... (

How accurate does the timestamp need to be? Unless it needs to be accurate
to the nearest second, you can just power up the system periodically to
check whether the glass tube is still intact.

This approach is commonly used for carbon monoxide detectors, which
typically take one measurement every 30 seconds and run for 5 years on the
supplied battery (which cannot be replaced, to ensure that the unit is
replaced as a whole; the sensor has a limited lifespan).

 

[Jamie]

The Brat dropped her Dell laptop yesterday, and lunched the hard
drive, including a powerpoint presentation that took 8 hours to do and
is due today. She called for help. I told her to head for Wal-Mart,
get a new pc, and start over. They had DElls and a Sony Vaio
available, and called me from the Wal-Mart and asked me which to buy.
The Sony of course. It has mems accelerometers inside that detect
zero-G and retract the disk heads before impact.

1G = not falling

0G = falling

John

but, i don't think that works unless it's powered up. The poster wants
it to work even with the batteries out.
That would imply a mechanical release snap switch which works with
sudden stops how ever, the one's i've seen are not small because they
need a little inertia to make it work.

 

[Jamie]

We need to have a time stamp (to be able to properly assign
blame ;o) ) - glass tubes won't do.
I do not know:
a. "how much is too much?"
b. How to keep this system running for, say, two months between
recharges on whatever tiny volume available for the battery. The
minimum I will need (I have found so far is) ~1..1.5Amp-hour cell.
It's not tiny... (

what you need is a small "inertia switch" mounted on a small mini
board or maybe part of your main board to be operating by a back up
batter which maintains a low power pic or like that with a TOD clock in
it that supports a calendar.

inertia switches are very popular and are getting small.
You could most likely construct a complete potted unit with a
proprietary plug in device that only you would have the resources to
connect to.
I've seen this in medical devices so that only the manufacturer that
made the equipment could connect up to it and down load information
about service times and may other things that we don't want to know
about. These devices normally have their own batteries in the potting of
the device.

 

[John Larkin]

<rolls eyes> You are quite serious when you say that?

If we put him in a box, do you think he could tell if he was
stationary, or falling?

John

 

[Michael]

How accurate does the timestamp need to be? Unless it needs to be accurate
to the nearest second, you can just power up the system periodically to
check whether the glass tube is still intact.

This approach is commonly used for carbon monoxide detectors, which
typically take one measurement every 30 seconds and run for 5 years on the
supplied battery (which cannot be replaced, to ensure that the unit is
replaced as a whole; the sensor has a limited lifespan).

Ahah! This is interesting idea: use disposable detector and check it
every once in a while. Thank you, I'll look into it...

 

[Tim Williams]

If we put him in a box, do you think he could tell if he was
stationary, or falling?

Nah, put him in the box with a radiation-activated cyanide source. Then
open the box and view his wavefunction.

Tim

 

[Jon Slaughter]

If we put him in a box, do you think he could tell if he was
stationary, or falling?

The vomit comet is a good example. We know they are in free fall but to them
they are in 0g. (Of course they know its free fall only by deduction)

If you jumped out of a plane with your eyes closed and there was no
atmosphere then you would not know your falling but you would think you are
floating(exactly like the vomit comet... the plane itself acting to isolate
you from the atmosphere) until you hit the ground.

I don't mean that you cannot detect acceleration but simply that you cannot
tell the difference between different "kinds". Although I suppose for
practical considerations it doesn't matter much. A 24k solid gold handheld
probably will never end up in the vomit comit. Also I seriously doubt that
he's really interested in detecting "free fall" but impact(my guess is to
void the warranty).

Although, for example, if someone took the handheld on a plane its possible
that it might detect "free fall" if it was not designed properly(or maybe
that would need to be a dragster?).

 

[Jim Stewart]

The vomit comet is a good example. We know they are in free fall but to them
they are in 0g. (Of course they know its free fall only by deduction)

If you jumped out of a plane with your eyes closed and there was no
atmosphere then you would not know your falling but you would think you are
floating(exactly like the vomit comet... the plane itself acting to isolate
you from the atmosphere) until you hit the ground.

I think you'd perceive it the other way - in
weightlessness or jumping out of an aircraft
without an atmosphere you'd think you were falling,
at least until you were conditioned to the effect.

We're well-programmed to expect 1 gee downwards
all the time.

 

[mpm]

I need to find a way to detect whether our hand held instrument ($25k-
$40k) was abused (dropped, bumped, etc).
It means free fall and shock detection (detect, timestamp, go back to
sleep). First one is relatively simple. "Relatively" because this
shock_detection_system needs to rely on it's own battery - the
instrument may be dropped when main battery is out and this "battery
out" state may be as long as two months. And occupy no (ok, very low)
volume.
Shock detection is what I need help with. I found out (http://www.isthq.com/main.asp?a=2&b=0&pageid=86&view=active) that 25G is
"small" shock. This gives some clues - shock detector will not
necessarily be able to see free fall - two different devices - ???
"...You have a tough job ahead of you. I know of no technology that
will get you the kind of low power performance you want without a lot
of pain. We do not offer anything like that...." - response from the
accelerometer manufacturer tech support.
I have EE background and my knowledge of physics is limited.
To add insult to the injury: we do not know how much shock our
instrument can sustain without losing performance.
Can anybody point me in the right direction?

Thanks!!

I don't know.?
For the "abuse" part of this, you can probably arrange "lie-detection"
services with a local company. If you suspect purposeful employee
abuse, that alone might solve the problem (i.e., fear of losing one's
job.)

And would probably be cheaper and better in the long run.
(Besides, you could ask other questions - like who's sleeping with
whom, who's on drugs, who's stealing from the Company, stuff like
that.)

-mpm

 

[John Larkin]

I think you'd perceive it the other way - in
weightlessness or jumping out of an aircraft
without an atmosphere you'd think you were falling,
at least until you were conditioned to the effect.

We're well-programmed to expect 1 gee downwards
all the time.

Except on Monday mornings, when it's 1.8.

John

 

[Ross Herbert]

I need to find a way to detect whether our hand held instrument ($25k-
$40k) was abused (dropped, bumped, etc).
It means free fall and shock detection (detect, timestamp, go back to
sleep). First one is relatively simple. "Relatively" because this
shock_detection_system needs to rely on it's own battery - the
instrument may be dropped when main battery is out and this "battery
out" state may be as long as two months. And occupy no (ok, very low)
volume.
Shock detection is what I need help with. I found out (http://
www.isthq.com/main.asp?a=2&b=0&pageid=86&view=active) that 25G is
"small" shock. This gives some clues - shock detector will not
necessarily be able to see free fall - two different devices - ???
"...You have a tough job ahead of you. I know of no technology that
will get you the kind of low power performance you want without a lot
of pain. We do not offer anything like that...." - response from the
accelerometer manufacturer tech support.
I have EE background and my knowledge of physics is limited.
To add insult to the injury: we do not know how much shock our
instrument can sustain without losing performance.
Can anybody point me in the right direction?

Thanks!!

You need Shockwatch
http://www.shockwatch.com/pdfs/SWCL1-06_s_and_h_monitors.pdf

 

[neon]

the best place is the USA goverment for A SOURCE of their tests. There is E.M.I, SHOCK, VIBRATION, SPEED, TEMPERATURE, ALTITUDE, HIPOT, DROP AND FINALY TEMPEST. THEY DO IT ALL.