[Greg McKaskle]

As mentioned, gyros are not perfect or magic. They are a sensor circuit and are affected by a number of real-world issues such as electrical noise, temperature, and operating procedures.

Electrical noise: The heart of the sensor is an element that affects the voltage of the circuit proportional to rotational movement. Electrical noise and power dips on the input circuit look like rotation.

Temperature: The sensor's gain changes with temperature. When you boot the robot, it calibrates. If the temperature changes substantially, the sensor's assumptions are off and it will increase drift. The data sheet should indicate the amount of the temperature effect.

Procedures: It is important that the robot be steady when the program boots because it is measuring for a few seconds to identify what voltage correlates to a rotation of 0. If the robot is moving at this point, the assumptions are wrong and the gyro will spin at the opposite of that "zero" rate.

Another procedural issue is that the gyro has an upper limit on rotation. If you exceed this limit, it under-reports the rotation and throws off your idea of where the robot is pointing.

With all of these issues handled correction, it will drift, but for short periods of time, like during auto, or when aiming, you can use it for relative turning measurements.

Greg McKaskle