Yaw angle keep on changing for 10 DOF Mems IMU Sensor

HI there
I bought 10 DOF Mems IMU Sensor . and when I was using the code which is provided by DF Robot I noticed that the yaw angel is keep on increasing or decreasing. SO how to use the magnetometer to fix this error ?
Regards
Abdul
I bought 10 DOF Mems IMU Sensor . and when I was using the code which is provided by DF Robot I noticed that the yaw angel is keep on increasing or decreasing. SO how to use the magnetometer to fix this error ?
Regards
Abdul