What's the difference between an X/Z and an X/Y 2-axis gyro?

[EricVanWyk]

I can't find a datasheet for the IXZ-500 - all the links point to a deleted page. Can you direct me better?

From page 5 of http://www.sparkfun.com/datasheets/C...eet_IDG500.pdf, both axes are along the surface of the PCB.

[Randy Forgaard]

Hi, Eric. Sorry about the broken link to the IXZ-500 X/Z 2-axis gyro on the SparkFun site and even on the manufacturer's site. Here is the correct link to the IXZ-500 datasheet.

Thanks so much for mentioning Page 5 of the IDG-500 X/Y gyro datasheet. I looked at that page, and I now see the little diagram in the lower-right corner of that page that shows what they mean by X-axis and Y-axis. Their X-axis is what I would call "pitch," and their Y-axis is what I would call "roll." I just now compared that to the corresponding diagram on Page 5 of the IXZ-500 X/Z gyro datasheet, their Z-axis is what I would call "yaw."

Since, for our robot, we are looking for "yaw" and "pitch" measurements, we want the IXZ-500 X/Z gyro. And rotating that IXZ-500 X/Z gyro circuit board 90 degrees would NOT be the same as an X/Y gyro. That is why they needed to make separate chips.

Your question back to me helped me answer my own question. Much appreciated! It all came down to a misunderstanding on my part -- I thought X/Y/Z was yaw/roll/pitch, but (at least as far these gyros is concerned) X/Y/Z is pitch/roll/yaw.

I'm all set. Thanks again!

[Bob Steele]

I might be wrong about this but I believe the difference is that in an XY gyro you have the two axes oriented in the same plane as the board.
In an XZ gyro the one axis is in the plane of the board and the other is normal to it.

I think that is the difference...

[Randy Forgaard]

Hi, Bob. Yes, what you say does indeed seem to be correct. From Eric's email, I discovered a little diagram in the datasheets for both the X/Z gyro and the X/Y gyro that showed what they mean about the X, Y, and Z-axes.

My confusion stemmed from the fact that I thought that X/Y/Z was yaw/roll/pitch, but (at least as far these gyros is concerned) X/Y/Z is pitch/roll/yaw. That explains why an X/Y gyro is not simply a 90° rotated X/Z gyro -- they are fundamentally different parts, because the Z-axis (the yaw) is in a plane that is normal (orthogonal) to the plane of the X-axis (pitch).

I'm all set. We went ahead and ordered the X/Z gyro, and we're excited to receive it and give it a try. Thanks for your note!

[DonRotolo]

Originally Posted by Randy Forgaard

Okay, now imagine that we take that X/Z 2-axis gyro, mounted on its little circuit board, and we rotate the whole board 90 degrees, horizontally, in the same plane as the circuit board itself.

Then instead of an X/Z gyro you get an Y/Z gyro. The Z axis goes straight up through the board.