The work reported here is concerned with methods used to provide partial pose data for robot calibration tests. Rather than focussing on traditional, precision measurement techniques, the paper discusses calibration using end point motion constraints of various kinds. The preferred method consists of using a wire potentiometer attached to the robot tool by means of two specially designed fixtures. Suitable modeling of the measurement system as well as the internal kinematics of the manipulator allows simulation of the calibration process. Experimental results obtained in the calibration of an industrial manipulator is presented, and means to make the complete calibration process automatic is discussed.>