accelerometer vs gyroscope in smartphones

Replies

• 

  Ramani Aswath

  A gyro is a mechanical device, like a spinning wheel or a vibrating reed, neither of which is in a cell phone.
• 

  Harshad Italiya

  There are chips available that can have both Accelerometer and Gyroscope both and may be that is used in mobile phones.
  
  Basic difference between Accelerometer and Gyroscope is Gyroscope uses Earth’s gravity to help determine orientation while Accelerometer measures non-gravitational acceleration.
  
  So now what exactly is your final goal with Gyroscope if you just want to do movement detect then you can do that with Accelerometer also.
• 

  Ramani Aswath

  Harshad, I think that there may be a semantic issue here. A gyroscope is a device that maintains a fixed orientation in space unless an external force is applied. When that happens it precesses. I think that the term is loosely used in the context of the chip that you mentioned.
• 

  Harshad Italiya

  A.V.Ramani

  Harshad, I think that there may be a semantic issue here. A gyroscope is a device that maintains a fixed orientation in space unless an external force is applied. When that happens it precesses. I think that the term is loosely used in the context of the chip that you mentioned.

  Did you mean Gyroscope can't be a small electronic chip?
  See this chip is having Gyro+Accelerometer Sensor inbuilt:- www.sparkfun.com
• 

  Harshad Italiya

  This chips called MEMS - Micro-Electro-Mechanical-System
• 

  Ashraf HZ

  Harshad Italiya

  This chips called MEMS - Micro-Electro-Mechanical-System

  I used to blog about MEMS back in 2008. I once applied to an online tech website and sent a sample of my MEMS writing. They reverted saying MEMS was too "scientific" for them and not mainstream at the time. Haha. We've come a long way since then.
• 

  Harshad Italiya

  ash

  They reverted saying MEMS was too "scientific" for them and not mainstream at the time. Haha. We've come a long way since then.

  If you are talking about 2008 then yeah I think that was the time when MEMS was not that much known to everybody. But look at the time now !
• 

  Ramani Aswath

  Harshad Italiya

  But look at the time now !

  My involvement with (Mechanical) Gyroscopes dates back to 1953 in the Physics lab. I have a toy called Levitron based on this principle right now. It is a levitating spinning top.
  I am sure all of us have suffered the common house fly landing on the nose. If you shoe it away it returns back to the same spot on the nose. The fly has two vibrating reed gyroscopes under each wing that keeps track of where it was.
  
  We do use some mems in our work on medical devices. I have never heard of gyros in a chip.
  
  In any case the physics of gyros is the same whether it is a giant gyro or a fly's wing gyro. Have you any idea of the actual mechanism in the mems chip. Is it a vibrating slicon wafer or some such? What keeps it going?
• 

  Harshad Italiya

  Yes,
  I have read about accelerometer and that is having spring inside. But for gyro it need more additional vibrating wafer/ spring which gives mechanical things and variable capacitance and resistance gives electronic part.
  
  Will do some more study on this as now a days they usually do x-ray of such chips when gets reported with bugs related to EMC EMI
• 

  Ashraf HZ

  This video neatly explains how the MEMS gyroscope works.
  
  In summary:
  - Drive capacitors vibrate silicon proof masses along X & Y axes, with fixed velocity and opposite directions
  - Once angular velocity is applied due to rotation, sense capacitors measure the proof masses displacement due to the resultant vector of the proof masses vibration velocity and angular velocity
  - The direction & rate of rotation is calculated from the sense capacitors delta for each axis.
  - More nuances of the design (such as measuring the yaw on Z axis) is explained in the video.
  
  
• 

  Ramani Aswath

  So it is a vibrating mass gyro, which is understandable. Thanks, Ash.