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Using many cheap accelerometers to reduce error

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Guest

Tue Feb 12, 2019 3:45 am   



bill.sloman_at_ieee.org wrote in
news:8560b6a4-5b20-4bec-b42d-5f2651a3980d_at_googlegroups.com:

Quote:
On Tuesday, February 12, 2019 at 2:01:40 AM UTC+11,
DecadentLinux...@decadence.org wrote:
bill.sloman_at_ieee.org wrote in
news:14361849-d4c5-4f3a-a6b9-7b65f2ac7300_at_googlegroups.com:

Depend when the value is marked on the resistor - before or
after measurement.


He said E12 series.

Resistors all follow a standard progression in values.

Usually a full deviation from center spec will NOT take the
part into
the next value bin.

If the resistor gets its value marking before its resistance was
measured, you wouldn't put it into the next bin up, even if it did
measure out as qualifying.

snip


Precision resistors get matched and culled before any markings are
applied. Some even get laser trimmed to spec.

Precision SMTs usually do not even have a marking.


Guest

Tue Feb 12, 2019 4:45 am   



On Sun, 10 Feb 2019 22:23:10 -0800 (PST),
gnuarm.deletethisbit_at_gmail.com wrote:

Quote:
On Sunday, February 10, 2019 at 7:51:42 PM UTC-5, k...@notreal.com wrote:
On Sun, 10 Feb 2019 08:28:39 -0800 (PST),
gnuarm.deletethisbit_at_gmail.com wrote:

On Sunday, February 10, 2019 at 10:57:41 AM UTC-5, John Larkin wrote:
On Sat, 9 Feb 2019 21:58:58 -0800 (PST), JS <js5071921_at_gmail.com
wrote:

On Sunday, February 10, 2019 at 1:13:07 AM UTC+2, John Larkin wrote:
On Sat, 9 Feb 2019 12:47:28 -0800 (PST),
wrote:

Hi all,

Given that the random error in a sample is proportional to 1/sqrt(sample size), does having many accelerometers and then averaging their output therefore reduce their overall error?

So would it be worthwhile to have say 100 or 1000 cheap accelerometers rather than one expensive one like a laser ring gyro?

Thanks.

sqrt(1000) is only 32. I'd expect the ring gyro to be vastly better
than a cheap MEMS or some such.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

OK I did the sums. Based on the random walk of a laser ring gyro (0.0035 deg/sqrt-hour) and that of a MEMS accelerometer (2.25 deg/sqrt-hour) [1], you need about 400k MEMS accelerometers to approach the accuracy of a laser ring gyro.

It sounds like a lot of components to solder together but if done in a chip fab, it should be possible.

Is it possible to make a commercial accelerometer with no export restrictions by using such an array? Or will ITAR or the like be slapped on such a device once its accuracy is published in a brochure?

Refs:
[1] Honeywell GG1320AN Digital Laser Gyro brochure
[2] Error and Performance Analysis of MEMS-based Inertial Sensors with a Low-Cost GPS Receiver. Park, M & Gao, Y. [2008] Sensors Vol 8

If the MEMS parts use vibrating cantilevers, they would want to sync
up. I don't know if that is good or bad.

They might "want" to sync up, but I'm not sure they would. If the platform has rotational acceleration there would be a difference in the acceleration on each device depending on it's distance from the center. That would keep them out of sync.

Would it? If they're on the same platform, the coupling is the same
no matter what additional force is on them (superposition).

Eh? If there is rotation each sensor will have a separate acceleration with different distances from the center of rotation. The different forces stimulate the different sensors to different frequencies. Don't the frequencies vary with force?

Is it or is it not a linear system? Ever hear of superposition?
Didn't think so.


Guest

Tue Feb 12, 2019 10:45 am   



On Tuesday, February 12, 2019 at 2:22:56 PM UTC+11, k...@notreal.com wrote:
Quote:
On Sun, 10 Feb 2019 22:23:10 -0800 (PST),
gnuarm.deletethisbit_at_gmail.com wrote:

On Sunday, February 10, 2019 at 7:51:42 PM UTC-5, k...@notreal.com wrote:
On Sun, 10 Feb 2019 08:28:39 -0800 (PST),
gnuarm.deletethisbit_at_gmail.com wrote:

On Sunday, February 10, 2019 at 10:57:41 AM UTC-5, John Larkin wrote:
On Sat, 9 Feb 2019 21:58:58 -0800 (PST), JS <js5071921_at_gmail.com
wrote:

On Sunday, February 10, 2019 at 1:13:07 AM UTC+2, John Larkin wrote:
On Sat, 9 Feb 2019 12:47:28 -0800 (PST),
wrote:

Hi all,

Given that the random error in a sample is proportional to 1/sqrt(sample size), does having many accelerometers and then averaging their output therefore reduce their overall error?

So would it be worthwhile to have say 100 or 1000 cheap accelerometers rather than one expensive one like a laser ring gyro?

Thanks.

sqrt(1000) is only 32. I'd expect the ring gyro to be vastly better
than a cheap MEMS or some such.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

OK I did the sums. Based on the random walk of a laser ring gyro (0.0035 deg/sqrt-hour) and that of a MEMS accelerometer (2.25 deg/sqrt-hour) [1], you need about 400k MEMS accelerometers to approach the accuracy of a laser ring gyro.

It sounds like a lot of components to solder together but if done in a chip fab, it should be possible.

Is it possible to make a commercial accelerometer with no export restrictions by using such an array? Or will ITAR or the like be slapped on such a device once its accuracy is published in a brochure?

Refs:
[1] Honeywell GG1320AN Digital Laser Gyro brochure
[2] Error and Performance Analysis of MEMS-based Inertial Sensors with a Low-Cost GPS Receiver. Park, M & Gao, Y. [2008] Sensors Vol 8

If the MEMS parts use vibrating cantilevers, they would want to sync
up. I don't know if that is good or bad.

They might "want" to sync up, but I'm not sure they would. If the platform has rotational acceleration there would be a difference in the acceleration on each device depending on it's distance from the center. That would keep them out of sync.

Would it? If they're on the same platform, the coupling is the same
no matter what additional force is on them (superposition).

Eh? If there is rotation each sensor will have a separate acceleration with different distances from the center of rotation. The different forces stimulate the different sensors to different frequencies. Don't the frequencies vary with force?

Is it or is it not a linear system? Ever hear of superposition?
Didn't think so.


Krw's capacity not to think is remarkable, and frequently demonstrated, as here.

With anybody else you'd have to wonder what they were thinking, but krw doesn't think - he just consults his preprogrammed attitudes. Rick isn't a right-wing lunatic so he has to be wrong ...

--
Bill Sloman, Sydney

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