can also be introduced by rotational torques generated by a motorised probe head one example is the reaction torque generated by a motorised servo positioning probe head which is itself in motion and taking measurements at the same instance in such a situation the probe head can be dynamically distorted from its nominal position due to the torsional bending of the cmm since torque generated by a motorised head is taken back to earth through the cmm structure the process described under the heading u201c correcting translational and rotational errors u201d will measure the amount of angular displacement at the probe head and so correct the measurements obtained from a motorised probe head 39 s rotary encoder system currently available accelerometers measure acceleration in either one two or three axes there are many different permutations for placing these sensors depending on their type and measurement axis the simplest method of measuring acceleration on the probe head in three orthogonal axes is with a 3 axis accelerometer or 3 single axis accelerometers shown in fig2 a rotation about each of the three orthogonal axes can either be measured using gyroscopes or additional accelerometers fig2 b shows a configuration using 3 gyroscopes and a 3 axis accelerometer configurations using single dual and three axes accelerometers to measure both translation and rotation are shown in fig2 c 2 d amp 2 e six degrees of movement 3 translation and 3 rotation is derived by combining the measurements from different sensors equations for a six single axis accelerometers configuration fig2 c are a x u2062 a z1 a z2 2 a y.