The nearest references for analysing articulated arms as measurement instruments are the robots; these last are ordinarily analysed for operations of power, for dynamic purposes, or for intelligent tasks like the avoidance of obstacles; but rarely are analyzed as distorted and deformable devices. Problems of inverse kinematics involved in robotics are augmented, when small distortions of joints, arms or encoders are necessary to know for assuring their accuracy in the level of micrometers. When a whole map of their errors is defined, numerical corrections of measures are possible to apply. This work proposes models describing their distortions, and strategies to define them throughout simulated calibrations, numerical techniques and physical tests.