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Great Stocking Stuffer

Posted: Fri Dec 19, 2008 4:40 pm
by Larry Andrews
http://www.woodcraft.com/product.aspx?P ... 4&hp9=true

Just got one. Works great - small, mag base, reads to a tenth and dirt cheap compared to anything comparable that I know of.

Any other fun ideas?

Re: Great Stocking Stuffer

Posted: Fri Dec 19, 2008 5:04 pm
by Eric Clements
Make sure your table is level...

Re: Great Stocking Stuffer

Posted: Sat Dec 20, 2008 1:57 am
by Mako Koiwai
Let us know how it works as a Camber Gauge ... against a straight edge/tire :ibrightdea:

Re: Great Stocking Stuffer

Posted: Sat Dec 20, 2008 10:20 am
by Steve Collins
Is it really repeatable to 0.1 deg?

In other words, if you set it on something solid and take multiple readings, are they all within +-0.1 of each other, e.g.

0.3
0.4
0.3
0.4
0.3


or does the reading jump around more than that:

0.3
0.0
0.5
0.2
0.6
0.4

If it's really accurate to 0.1 deg, I'm going to buy one to use on the Mars rover.

steve

Re: Great Stocking Stuffer

Posted: Sat Dec 20, 2008 11:49 am
by Eric Clements
Steve Collins wrote:If it's really accurate to 0.1 deg, I'm going to buy one to use on the Mars rover.
Just watch out for the shipping costs!

Re: Great Stocking Stuffer

Posted: Sat Dec 20, 2008 12:49 pm
by Larry Andrews
Steve Collins wrote:Is it really repeatable to 0.1 deg?
It's pretty close to the first distribution. One to two tenths seems like a reasonable tolerance. Because it's small, it is quite sensitive to surface variation - which can be both a good thing and a bad thing depending on what you're trying to use it for. My place has plaster walls and it easily finds the ripples in the surface that I can't see but my hand can feel.

I did trim a tiny sliver off the rubber surround with an X-acto that caused a barely perceptible wobble so now it sits stably on the extruded case. There's a bit more rubber going past the two sides that still needs to be trimmed - all of 30 seconds work.

Just spent time zeroing it on a VPI turntable that I'd carefully leveled with a bullseye. It repeatably finds zero when I put it back on the platter. I haven't done a real gage R&R with it to determine the full accuracy of the MEMS gyro.

Steve - if you work with the Rover, please do me a favor and say hi to Gerke for me. :) Sadly, I'm going to miss their xmas party tonight. :(

Eric - LOLsers That was pretty funny - didn't see that one coming.

Mako - that's exactly what I had in mind when I bought it...am guessing that I'll need to use it kart-style and not worry about exact numbers and just compare relative measurements to track data but I suppose that it's possible that I'll find a way to get direct camber measurements.

Anybody want to buy an Intercomp camber gauge?

Re: Great Stocking Stuffer

Posted: Sat Dec 20, 2008 4:21 pm
by Steve Collins
Wow. Pretty impressive if it's repeatable to something like +0.2 deg for $30. I would guess that it's probably a pair of accelerometers rather than a gyro. The description implies that there is a button to "zero" it, so (once you have used it to verify that it's own case is square) I think you should be able to use it to measure the sum of the camber on both sides of the car. This should work even if the ground is not level (but won't give you information about whether the camber on both sides of the car is equal.)

Not sure I know your pal but it's a big place. Does he work on MER or MSL?
steve

Re: Great Stocking Stuffer

Posted: Sat Dec 20, 2008 10:46 pm
by Larry Andrews
Dono about the sensor - have heard that ring gyros are down to a few bucks now so I just assumed that's what they used. (I'm also a bit biased as I worked on one of those parts some time ago) Pair of accelerometers makes perfect sense too and is probably a cleaner design.

Everybody I know at JPL is in chip packaging and/or reliability. Birds of a feather... Have no idea what projects they're on.

Re: Great Stocking Stuffer

Posted: Sun Dec 21, 2008 9:26 am
by Will Kalman
Larry Andrews wrote:have heard that ring gyros are down to a few bucks now ....
http://www.sparkfun.com/commerce/produc ... cts_id=730" onclick="window.open(this.href);return false;