Accelerometers

1. Accelerometers Richard Manning

2. Accelerometers in General In general, an accelerometer is a device that is used to measure its own acceleration in comparison to a reference based on remote sensing.

3. What Accelerometers are Ripping Off The accelerometer is essentially a mechanical duplicate for the balance organs inherent in many organic species. Examples include: -Human inner ear -Aquatic invertebrate statocysts

4. Common Types of Accelerometers -Strain Gauge -Surface Micromachined Capacitive -Electromechanical Servo -Magnetic Induction -Thermal (through submicron CMOS process) -Resonance This is a micromachined accelerometer

5. Other Types Accelerometers -Laser Accelerometer -Surface Acoustic Wave -Optical -Piezo-film or piezoelectric sensor -Bulk Micromachined Capactive

6. Styles of Accelerometers Accelerometers are available in many different styles of packaging and output. Common types are: -Ratiometric Analog -Sensing Mv/g -Absolute Analog -Sensing Mv/g -PWM -Sensing % duty cycle/g

7. Common Uses for Accelerometers One of the most common places that accelerometers are found is in the automotive industry. They are used to determine when collisions occur and when to trigger the air bags. This is a graph of automotive accelerometers and shows the difference between normal automobile operation and a collision. A single accelerometer can replace between 3 to 5 g switches. An accelerometer designed by the Archimedes Automated Assembly Planning Project at Sandia National Laboratory

8. Accelerometers Where you Would not Think Nintendo has confirmed that the upcoming Wii pointer makes use of accelerometers to drive its tilt and pointing capacity. Also, the nunchaku controller add on also has accelerometers built in to enhance gameplay.

9. Accelerometer Drawbacks -Accelerometers can get expensive when needed to operate in high temperatures -Accelerometers can have some difficulty working with tilt signals when acceleration is occurring -Accelerometers can generate noise that can hurt their signal resolution -Accelerometers can not tell the difference between tilt and motion, but no sensor currently can either

10. Things to Remember for Choosing Accelerometers -Determine the temperature range at which the sensor must operate -Determine the power demands of the sensor -Determine the voltage output when the sensor is at its neutral position -Decide what sensitivity you need -Decide how much variance in sensitivity is acceptable if rapid temperature shifts are to be expected -Acceleration is a vector that the accelerometer measures along its sensitive axes

11. Accelerometers in Recap -Accelerometers are devices that are used to measure their movement in comparison to a reference based on remote sensing. -They are many different types of accelerometers -Accelerometers are used in many places, including the automotive industry and in many consumer electronics -There are several different ways that accelerometers can measure their movement, including PWM, Ratiometric analog, and absolute analog -They range greatly in cost and in resolution

12. Sources www.analog.com/Analog_Root/static/library/techArticles/mems/Sensor971/sld5.html http://en.wikipedia.org/wiki/Accelerometer www.societyofrobots.com/sensors_accelerometer.shtml www.memsic.com/memsic/products/search_xlkuang.asp www.vernier.com/probes/acc-group.html

13. Questions