# Inertial Sensor (IMU) ![](https://3510336827-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M7yGVyBrcpSR8SDSikj%2Fuploads%2FTVUt16r0U4KrPX2RURrb%2Finertialsensor.png?alt=media\&token=1f6a00d6-b613-4d8b-8693-5fe51eb1d249) The V5 Inertial Sensor is a combination of a 3-axis (X, Y, and Z) [accelerometer](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/accelerometer) and a 3-axis [gyroscope](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/gyroscope). The accelerometer will detect a change in motion (acceleration) in any direction and the [gyroscope](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/gyroscope) electronically maintains a reference position so it can measure a rotational change of position in any direction against this reference. A detection of a change in motion can help decrease the chance of a robot falling over when it is driving or while it is climbing over an obstacle. The housing of this sensor has a single mounting hole which allows it to be easily mounted to the robot’s structure. In addition, there is a small indentation in front of the mounting hole which marks the sensor’s reference point. On the bottom of the housing, there is a round boss which is sized to be inserted into a square hole of a piece of structural metal. This will keep the sensor fixed to its attachment point. On the back of the sensor housing is a V5 Smart Port. Both the [accelerometer](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/accelerometer) portion and the [gyroscope](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/gyroscope) portion of this sensor produce a smart signal feedback to the V5 Brain. ### [**Accelerometer**](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/accelerometer) The [accelerometer](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/accelerometer) measures how fast the sensor changes its motion (accelerates) along the X-axis, the Y-axis, and/or the Z-axis. These axis are determined by the orientation of the Inertial sensor. For example, one orientation could have a robot’s X-axis as its forward and backward motion, its Y-axis as its side to side motion, and its Z-axis as its up and down motion (such as the robot lifting itself up off the field on a suspension pole). The [accelerometer](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/accelerometer) measures a change in motion when its internal electronics detect a change in inertia and this creates a change in its reading. The faster the change in motion the more the reading changes. Note: This may be a larger positive value or a larger negative value depending on the direction of the motion along the axis. Acceleration is measured in g’s (unit of gravitational acceleration). The maximum measurement limit for the [accelerometer](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/accelerometer) portion of the Inertial Sensor is up to 4g. This is more than enough to measure and control most robot behaviors. ### [**Gyroscope**](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/gyroscope)**:** The [gyroscope](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/gyroscope), rather than measuring linear motion along the 3 axis, measures the rotational motion around the 3 axis. The sensor measures this rotation when the internal electronics create a fixed reference point. As the sensor rotates away from this reference point it changes the output signal. It takes a short period of time for a [gyroscope](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/gyroscope) to establish its reference point (calibration). This is commonly called the initialization or startup time. (Note: It is recommended using 2 seconds for a calibration time or start the sensor’s calibration within the pre-auton portion of the competition template. When using the sensor within the VEXcode V5 Blocks/Text drivetrain functions, the calibration is included within the function.) An electronic [gyroscope](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/gyroscope) also has a maximum rate of rotation. That is, if the object the sensor is measuring is spinning faster than the [gyroscope](https://wiki.purduesigbots.com/vex-electronics/vex-sensors/3-pin-adi-sensors/gyroscope) can measure its rotation, the sensor will return incorrect readings. The maximum rotation rate for the Inertial Sensor is up to 1000 degrees/second. Once again, this is more than enough to measure and control all but extreme robot behaviors. ## Teams Contributed to this Article: * [BLRS](https://purduesigbots.com/) (Purdue SIGBots)