Stepping Mechanism for X‐Ray and Neutron Diffractometers and Spectrometers

This motor is a permanent magnet type a-c motor with two field windings. As an a-c motor it has a speed of 72 rpm; however, when direct voltage is applied to the field windings, the motor will lock into a magnetic hold position, and if the voltage is then switched, the motor will advance pending upon the switching used. There is no need for braking since the accuracy of positioning each step is extremely great, and any inaccuracy of positioning is nonaccumulative. To control the amount of rotation, a transistonized electronic stepping motor control consisting of a pre-set counter and motor drive switohing circuit is used. The pre-set counter counts the number of drive pulses delivered to the motor by the switching circuit, and hence the amount of rotation of the motor shaft. After reaching the pre-set amount of rotation, the control automatically stops itself and resets the pre-set counter to zero. This control can be started and stopped manually or automatically and can also drive continuously. (N.W.R.)