.. include:: # Accelerometers - Hardware Accelerometers are common sensors used to measure acceleration. In principle, precise measurements of acceleration can be double-integrated and used to track position (similarly to how the measurement of turn rate from a gyroscope can be integrated to determine heading) - however, in practice, accelerometers that are available within the legal FRC\ |reg| price range are not nearly accurate for this use. However, accelerometers are still useful for a number of tasks in FRC. The roboRIO comes with a :ref:`built-in three-axis accelerometer ` that all teams can use, however teams seeking more-precise measurements may purchase and use a peripheral accelerometer, as well. ## Types of accelerometers There are three types of accelerometers commonly-used in FRC: single-axis accelerometers, multi-axis accelerometers, and IMUs. ### Single-axis accelerometers .. image:: images/accelerometers-hardware/adxl193-single-axis-accelerometer-to-roborio.svg :alt: The three wire connection from the Accelerometer to the Analog In port of the roboRIO. As per their name, single-axis accelerometers measure acceleration along a single axis. This axis is generally specified on the physical device, and mounting the device in the proper orientation so that the desired axis is measured is highly important. Single-axis accelerometers generally output an analog voltage corresponding to the measured acceleration, and so connect to the roboRIO's :doc:`analog input ` ports. ### Multi-axis accelerometers .. image:: images/analog-inputs-hardware/triple-axis-accelerometer-to-roborio.svg :alt: The triple axis accelerometer hooked up to three different Analog In channels. Multi-axis accelerometers measure acceleration along multiple spatial axes. The roboRIO's built-in accelerometer is a three-axis accelerometer. Peripheral multi-axis accelerometers may simply output multiple analog voltages (and thus connect to the :ref:`analog input ports `, or (more commonly) they may communicate with one of the roboRIO's :doc:`serial buses `. #### roboRIO built-in accelerometer .. image:: images/systemcore/roborio-accelerometer.svg :alt: The details of this accelerometer are printed on the roboRIO to the right of the NI logo. The roboRIO has a built-in accelerometer, which does not need any external connections. You can find more details about how to use it in the :ref:`Built-in Accelerometer section ` of the software documentation. ### IMUs (Inertial Measurement Units) .. image:: images/accelerometers-hardware/navx-imu-to-roborio-mxp.svg :alt: Show the NavX plugged in to the MXP port on the roboRIO. Several popular FRC devices (known as "inertial measurement units," or "IMUs") combine both an accelerometer and a gyroscope. Popular FRC example include: - [CTRE Pigeon IMU](https://store.ctr-electronics.com/gadgeteer-pigeon-imu/) - [Kauai Labs NavX](https://pdocs.kauailabs.com/navx-mxp/)