JMP Accelerometers and Accelerometers and How they Work How they Work Contents summary JMP Acceleration Fundamentals Acceleration Fundamentals What is Acceleration What are the units What is a g JM PDF document - DocSlides

Page 1
JMP Accelerometers and Accelerometers and How they Work How they Work Contents summary
Page 2
JMP Acceleration Fundamentals Acceleration Fundamentals What is Acceleration? What are the units? What is a “g”?
Page 3
JMP More Notes on Acceleration More Notes on Acceleration What is the time rate of change of velocity? slope slope slope slope
Page 4
JMP to fi v ty fr d tr Ti ( seconds st ance Tr avel ed ( et er s)
Page 5
JMP How to find acceleration from velocity Time (second s) ci ty (meter s/ second)
Page 6
JMP Acceleration v . Time Ti me (s ec onds) Acceleratio (m eters/sec^2)
Page 7
JMP Acceleration in Human Terms Acceleration in Human Terms What are some “g” reference points? Description “g” level
Page 8
JMP What’s the point? What’s the point? Why measure acceleration?
Page 9
JMP Common Types of Accelerometers Common Types of Accelerometers Sensor Category Key Technologies Capacitive Piezoelectric Piezoresistive Hall Effect Magnetoresistive Heat Transfer
Page 10
JMP What Type of Acceleration Sensor What Type of Acceleration Sensor Does TI Produce and why? Does TI Produce and why? Capacitive Acceleration Sensor “CAS CAS
Page 11
JMP Acceleration Sensor Terminology Acceleration Sensor Terminology +1g: 0g: -1g: Linearity: out out out Linearity
Page 12
JMP Acceleration Sensor Terminology Acceleration Sensor Terminology Sensitivity: Vcc: %Vcc: Sensitivit out out out
Page 13
JMP Example: Sensitivity & Linearity Example: Sensitivity & Linearity 1. 000 1. 200 1. 400 1. 600 1. 800 2. 000 2. 200 2. 400 2. 600 2. 800 -1 g P on out ut V out ( The or Ac Volts Linearity out out out Volts Sensitivit out out out
Page 14
JMP Acceleration Sensor Terminology Acceleration Sensor Terminology Ratiometric:
Page 15
JMP Important Setup Requirements Important Setup Requirements for your CAS Device for your CAS Device Ri gid Mounting No Loose Wires Weight of Sensor Don’t drop the sensor!
Page 16
JMP Effect of Tilt Effect of Tilt DC response sensors measure tilt. Mounting errors are therefore significant a 1 tilt in the 0g position creates an output error equivalent to a 10 tilt in the +1g or -1g positions 0g is the most sensitive to mounting errors
Page 17
JMP Why is device sensitive to Why is device sensitive to tilt in the 0g orientation? tilt in the 0g orientation? 0g Orientation +1g Position Gn Gx Gn=G* os( T g level going from 1g to some % of 1g Gn Gx Gn = G*Sin( T g level going from 0g to some value Conclusion: at 0g orientation, change in 1 Conclusion: at 0g orientation, change in 1 tilt causes 57x tilt causes 57x bigger change in sensor output versus bigger change in sensor output versus 1g or +1g orientation 1g or +1g orientation
Page 18
JMP Effect of Tilt on DC Accelerometer Effect of Tilt on DC Accelerometer CAS O tput Voltage Change with Position ange in Output (mV) 500mV/g Device Degrees
Page 19
JMP Typical Accelerometer Applications Typical Accelerometer Applications Tilt / Roll Vibration / “Roug h-road” detection Vehicle skid detection Impact detection Input / feedback for active suspension control systems
Page 20
JMP Summary Summary Acceleration is a measure of how fast the speed of something is changing It is used as an input to control systems Sensor voltage output should be determined as a percentage of voltage input for consistency The device is sensitive to tilt i the 0g position