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Hi, I have an application where I need to measure tilt angle and direction changes. Can anyone suggest a simple method for doing this. I have a digital compass, but it can't handle the tilt of +/-45degrees. Would a 2 or 3 axis accelerometer be able to measure tilt and direction changes? Any suggestions would be greatly appreciated. Regards Chris

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Three accelerometers, each mounted perpendicular to one another, will give you title, direction, and acceleration information. (Our inner ear uses the exact same science.) You can do it with one dual-axis accelerometer, and one sigle-axis, mounting them appropriately. Accelerometers such as the ADXL family from Analog Devices are sensitive to the DC component of gravity, which can be used to determine tilt. Things do get a little messy if your project is also in motion. You may need to get tricky in resolving what's motion and what's tilt. You also must accept unbounded error in direction. You can sense a direction change, but over time, the actual direction being pointed to (e.g. North by Northwest) cannot be accurately inferred because of error. You need a landmark system such as a compass to recalibrate the system. Both the ADXL202 and the ADXL150/250 can be readily interfaced to the BX-24. The '202 has a digital output that you read as a pulse width; the ADXL150/250 (the 150 is a single-axis device; the 250 a dual-axis device) has a linear analog output. See the May issue of Poptronix for a discussion of these, and code for interfacing an ADXL150 to a BX-24 chip. -- Gordon At 11:27 AM 7/13/2000 +1000, you wrote: >Hi, > >I have an application where I need to measure tilt angle and direction >changes. Can anyone suggest a simple method for doing this. I have a digital >compass, but it can't handle the tilt of +/-45degrees. > >Would a 2 or 3 axis accelerometer be able to measure tilt and direction >changes? Any suggestions would be greatly appreciated. > >Regards >Chris > >------------------------------------------------------------------------ >LOW RATE, NO WAIT! >Get a NextCard Visa, in 30 seconds! Get rates >as low as 2.9% Intro or 9.9% Fixed APR and no hidden fees. >http://click.egroups.com/1/6632/8/_/565855/_/963451957/ >------------------------------------------------------------------------

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On Thu, 13 Jul 2000 11:27:46 +1000, "Chris Parker" <> wrote: > I have an application where I need to measure tilt angle and direction > changes. Can anyone suggest a simple method for doing this. I have a digital > compass, but it can't handle the tilt of +/-45degrees. My solution to that problem is to use the 2-axis tilt chip (ADXL202) to tell me when the platform is within a specified range of level, and only trust the compass output at those times... Later, Jon -------------------------------------------------------------- Jon Hylands http://www.huv.com/jon Project: Micro Seeker (Micro Autonomous Underwater Vehicle) http://www.huv.com

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I have used the Humphrey LA01 or LA02 (one or two axis) since they have very small DC error/drift compared to most of the strain devices like the ADxxxx parts. Also, the cross axis error is low. They cost around $12 an axis. They will allow you to do what you want, but even their small (30 ug uncorrected) error integrates up to large distance errors quickly. A GPS and the accelerometers can complement each other nicely. The GPS is very accurate at low acceleration and large distances while the accelerometers are accurate at high acceleration. A differential GPS (can be set up by having one fixed GPS that gets it's data sent to the vehicle by RF and one on the vehicle) does everything very well except attitude. The accelerometers supply this. Michael Fellinger -----Original Message----- From: Chris Parker <> To: <> Date: Wednesday, July 12, 2000 7:32 PM Subject: [BasicX] measuring tilt and direction changes? >Hi, > >I have an application where I need to measure tilt angle and direction >changes. Can anyone suggest a simple method for doing this. I have a digital >compass, but it can't handle the tilt of +/-45degrees. > >Would a 2 or 3 axis accelerometer be able to measure tilt and direction >changes? Any suggestions would be greatly appreciated. > >Regards >Chris > >------------------------------------------------------------------------ >LOW RATE, NO WAIT! >Get a NextCard Visa, in 30 seconds! Get rates >as low as 2.9% Intro or 9.9% Fixed APR and no hidden fees. >http://click.egroups.com/1/6632/8/_/565855/_/963451957/ >------------------------------------------------------------------------

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