1. -Andreas Gabrielsen Mechatronics Spring 2014
Accelerometers
-Andreas Gabrielsen
Mechatronics Spring 2014
Temple run, viewing phone, sensing on missiles or planes

2. Components:
Housing: Attached to the object that you’re trying to find the acceleration of
Seismic Mass: The mass suspended within the housing by a spring.
How it works:
-When you move the housing, the mass lags behind from the acceleration of movement
-The displacement is a measurement of the magnitude of the acceleration
-Proper acceleration is measured: which isn’t necessarily the rate of change of velocity
Rather-it’s with regard to weight of the mass in the frame of reference.
SO: if the accelerometer is sitting straight up, it’s value should be 9.8m/s^2 or 1g.
If you were in free fall or in space, that same accelerometer should read 0g

3. Types of Accelerometers
Do-it-Yourself:
This example helps explain the phenomena even more clearly.
When you move faster, the ring will swing more to reflect your change in acceleration

4. Types of Accelerometers
Piezoelectric:
During movement, the acceleration (and resultant lagging) causes the mass to squeeze the piezoelectric material
-The produces a charge proportional to the exerted force.
-Since mass is constant and Newton’s second law: F=ma, we know that charge is proportional to acceleration

5. Types of Accelerometers
Capacitance:
(MEMS)
When there is an accelerative force the blue, flexible seismic mass moves and it’s fingers move between the green leads to make up a series of capacitors whose capacitance changes based on the magnitude of movement
We know that C=ε_r * ε_0* (A / d) and “d” is changing and C=q / V. Therefore, we can measure the voltage change proportionally to the change in capacitance (dependent on the acceleration’s change of “d”)
ε_r: dielectric constant. ε_0: electric constant
There are even some other types of accelerometers that I haven’t looked into that use
-Piezoresistive effect
-Hot air bubbles
-Light

6. Sparkfun Accelerometers

7. Omega Accelerometers

8. Omega Accelerometers

10. Questions