Camber smartphone electronic measurement accuracy & precisio

E

Elder Jones

Guest
As a simple quick check at home, sort of like checking the oil dipstick, is
the accuracy & repeatability of a smartphone yet sufficient to check
automotive camber?
 
On Fri, 24 May 2019 21:00:25 -0500, Elder Jones wrote:
As a simple quick check at home, sort of like checking the oil dipstick,
is the accuracy & repeatability of a smartphone yet sufficient to check
automotive camber?
Click to expand...

I'm sure it depends on how accurately you park the vehicle on the phone. :)

Jon
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38.238N 104.547W | @ jonz.net | Jonesy | FreeBSD
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It seems that recently said:

> I'm sure it depends on how accurately you park the vehicle on the phone. :)

The three measurements that we need to accuracy & precision of about a
tenth of a degree are caster, camber, and toe.
o Caster is a function of camber at ą20 degree angles
o Camber has a range of from 0 to about ~ą6° ~ą10'
o Toe has a far smaller range of about 0.05° to about 0.1° per wheel
[https://blog.bavauto.com/11758/bmw-and-mini-camber-and-caster-adjustment-how-to-street-track-best-tire-wear-diy-kit/]

Since toe can be more easily measured linearly, only tenths of a degree
accuracy & precision would be required for measuring Caster & for
calculating Camber.
[https://forums.bimmerforums.com/forum/showthread.php?1666987-1998-528i-REAR-Wheel-Alignment]

For toe, we can obtain linear equivalents simply by converting a factory
given front total toe spec of 0°5'ą10' and a factory given rear total toe
of 0°22'ą4' to a non-angular linear distance given just the tire diameter
a. P235/45R17 = (235)(2)(0.45)(1/25.4) + 17 or about 25.3"
b. Factory total front toe = 0°5'ą10' & factory total rear toe = 0°22'ą4'
c. Toe from tread centerline to vehicle centerline is half that
d. Individual toe to centerline is 1/2 of 0°5' = 0°2.5' (halving may not be needed though)
e. 0°2.5' divided by 60' is ~0.0417 decimal degrees
f. 17" diameter rims * tangent ~0.0417° = 0.0124"
g. 0.0124" is roughly about 3/256ths" (or about 0.3mm)
[https://www.bmwcca.org/forum/index.php?threads/1998-bmw-528i-front-end-alignment-specs.979/]

The rears, calculated similarly, would be ~0.33" for total toe in.
[https://robrobinette.com/ConvertToeDegreesToInches.htm>]

We could also use the sine instead of the tangent if we consider the radius
of the tire to be the hypotenuse (the linear measurements are likely to be
taken at right angles to the centerline of the car, or an imaginary line
through the steering axis parallel to same) not at right angles to the tire
centerline; but at these tiny angles sine and tangent are basically the
same anyway so that makes no significant difference where the major linear
measurement error is likely in the gravitational bowing of the typical tape
measure. Hence the toe measurement accuracy & repeatability is due more to
the fact that the tire isn't very large, and the factory-specified angle is
very small, causing even a miniscule difference in distance with the tape
measure to translate to a fairly large portion of the angle.
[https://forums.pelicanparts.com/porsche-911-technical-forum/213336-alignment-conversion-inches-degrees-help.html]

Given that both toe and caster can be derived from other measurements, the
only question at hand is for Camber degrees to be measured by a smartphone.

For Camber, tenths of a degree in repeatability & accuracy would be nice.
Does anyone here know if a typical smartphone can achieve that feat yet?

If not...
When do you think phones will be able to achieve that accuracy & precision?
 
On 5/25/19 10:13 AM, Elder Jones wrote:
If not...
When do you think phones will be able to achieve that accuracy & precision?
Click to expand...

Nice try, but most of us have enough sense to have this done
by someone with the correct equipment.


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com
 
On Sat, 25 May 2019 10:13:43 -0500, Elder Jones
<Elder@spambottrap.net> wrote:

For Camber, tenths of a degree in repeatability & accuracy would be nice.
Does anyone here know if a typical smartphone can achieve that feat yet?
Click to expand...

The MEMS accelerometer used in many smart phones is capable of 0.06
degrees of resolution (not accuracy). The device will need to be
calibrated against a 0 degree horizontal flat surface (easily done by
vertically rotating the MEMS sensor and adjusting for zero change) to
obtain such levels of camber accuracy. The limiting factor is the
sensor noise level.

ADXL213AE datasheet
<https://www.analog.com/media/en/technical-documentation/data-sheets/ADXL213.pdf>
The typical noise floor is 160 ľg/vHz, allowing signals
below 1 mg (0.06° of inclination) to be resolved in tilt
sensing applications using narrow bandwidths (<60 Hz).

Note that this MEMS sensor currently sells for about $32/ea which
makes it an unlikely candidate for a consumer grade smartphone.
<https://www.digikey.com/product-detail/en/analog-devices-inc/ADXL213AE/ADXL213AE-ND/669792>
There are probably better and cheaper sensors available.

If not.
When do you think phones will be able to achieve that accuracy & precision?
Click to expand...

When someone finds or creates a market for such a device.

You can try it yourself to see what can be achieved. There are many
electronic bubble level apps for Android and iPhone:
<https://play.google.com/store/search?q=bubble+level&c=apps>
Most seem to display in 1 degree resolution, but there are a few that
will display 0.1 degree resolution:
<https://play.google.com/store/apps/details?id=com.jonyups.poziomicagen>
I tried to use various Android apps for aligning satellite dishes,
where +/-0.5 degrees or better accuracy is the norm:
<http://www.learnbydestroying.com/jeffl/antennas/dish-new-install-project/>
but found that a digital angle level was more useful:
<https://www.google.com/search?tbm=isch&q=digital+protractor>

These look interesting:
<https://express.google.com/u/0/product/15900634407707968640_0_6099994>
High accuracy ą0.005°, high resolution 0.001°.
<https://express.google.com/u/0/product/KKmoon-DXL3/12101973972988473742_13025317009461916407_6099994>
High accuracy ą0.05°, high resolution 0.01°.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
Why does this idiot troll have any traction in this group whatsoever?

Any idiot that would use a cell-phone or any similar device to check critical measurements in a vehicle deserves exactly what it gets. The sad part, of course, is when it gets what it deserves, it is more than likely to take one-or-more innocents with it. Of course, one is entirely and fully entitled to compete for a Darwin Award, but not to threaten others in the process.

Peter Wieck
Melrose Park, PA
 
On 5/28/2019 2:05 PM, pfjw@aol.com wrote:
> Why does this idiot troll have any traction in this group whatsoever?

"Like"

--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

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