Accelerometer

Accelerometer

Mind Media

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Accelerometer

The Accelerometer measures accelerations (g) along 3 axis’s (X, Y, Z). Place the sensor anywhere, depending on where you would like to measure accelerations. The NeXus Accelerometer uses 3 AUX inputs and can therefore only be used with the NeXus-10 or NeXus-32.

What is an Accelerometer?

Accelerometers are devices that measure acceleration, which is the rate of change of the velocity of an object. They measure in meters per second squared (m/s2) or in G-forces (g). A single G-force for us here on planet Earth is equivalent to 9.8 m/s2, but this does vary slightly with elevation (and will be a different value on different planets due to variations in gravitational pull). Accelerometers are useful for sensing vibrations in systems or for orientation applications.

How to Connect to an Accelerometer:

For most accelerometers, the basic connections required for operation are power and communication lines. As always, read the datasheet to ensure proper connections are made.

Communication Interface:
Accelerometers will communicate over an analogue, digital, or pulse-width modulated connection interface.

  • Analog - Accelerometers with an analogue interface show accelerations through varying voltage levels. These values generally fluctuate between the ground and the supply voltage level. An ADC on a microcontroller can then be used to read this value. These are generally less expensive than digital accelerometers.
  • Digital - Accelerometers with a digital interface can either communicate over SPI or I2C communication protocols. These tend to have more functionality and be less susceptible to noise than analogue accelerometers.
  • Pulse-Width Modulation (PWM) - Accelerometers that output data over pulse-width modulation (PWM) output square waves with a known period, but a duty cycle that varies with changes in acceleration.

Power:

Accelerometers are generally low-power devices. The required current typically falls in the micro (µ) or milli-amp range, with a supply voltage of 5V or less. The current consumption can vary depending on the settings (e.g., power-saving mode versus standard operating mode). These different modes can make accelerometers well suited for battery-powered applications.

Additional Features:

Some accelerometers include features such as tap detection (useful for low-power applications), free-fall detection (used for Active Hard Drive Protection), temperature compensation (to increase accuracy in dead reckoning situations ) and 0-g range sensing, which are other features to take into consideration when purchasing an accelerometer. The need for these types of features on the accelerometer will be determined by the application in which the accelerometer is incorporated.

There are also IMUs (Inertial Measurement Units) available, which can include accelerometers, gyroscopes and even, occasionally, magnetometers into a single IC package or board. Some examples of this include the MPU6050 and MPU9150. These are commonly used in motion tracking applications and UAV guidance systems, where the location and orientation of an object are important.

Specifications:

  • Unit: mV
  • Parameter: Acceleration (g)


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