- FRC Game Manual
- FRC Game Q&A

# 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® 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 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

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 analog input ports.

### Multi-axis accelerometers

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 analog input ports, or (more commonly) they may communicate with one of the roboRIO’s serial buses.

#### roboRIO built-in accelerometer

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 Built-in Accelerometer section of the software documentation.

### IMUs (Inertial Measurement Units)

Several popular FRC devices (known as “inertial measurement units,” or “IMUs”) combine both an accelerometer and a gyroscope. Popular FRC example include:

- Analog Devices ADIS16448 and ADIS 16470 IMUs

- CTRE Pigeon IMU

- Kauai Labs NavX