Designing Embedded Hardware, 2nd Edition

Accelerometer

Now we're going to take a look at an interesting sensor. Analog Devices makes some really nice accelerometers, and we'll learn how to interface an ADXL150 to an embedded system. You can use an accelerometer for a number of applications, not just for measuring linear acceleration of vehicles. The ADXL150 is a single-axis (one- dimensional) accelerometer with a resolution of 10 m g and a full-scale range of ±50 g. For dual-axis (two-dimensional) sensing, choose the ADXL250.

Tip

g is the unit of acceleration. One g is approximately equal to 9.8 m/sec² (32.2 feet/sec²). As a passenger in a commercial jet aircraft, you'll experience a force of about 2 g when the aircraft turns. A fighter aircraft will experience a force of around 8 g when turning sharply. Without a special suit, the jet fighter pilot would black out under a force of 8 g. So the ADXL150, with a range of ± 50 g, can measure a significant amount of force!

Such a fine resolution means you can use this sensor to measure gentle vibrations and shifts. You could use it in a seismometer for geophysical applications or to measure vibrations or ground shift in mines, tunnels, or at building sites. You could use it to monitor motion and, by placing three accelerometers orthogonally, get an accurate 3-D motion recorder. The same setup could also be used as a digital carpenter's spirit level by sensing the direction of the Earth's gravitational field. Perhaps you might use it to monitor violent physical shock, such as ...