MASSACHUSETTS INST OF TECH CAMBRIDGE CRYSTALLOGRAPHIC LAB
A computer ODFAC was constructed to sum Fourier series having up to 30 terms. The resolvers chosen for use in this computer enable an angle 0 to be transformed electrically into a trigonometric function. Each amplitude is set by a variac which regulates the input to a particular reoslver. The frequencies are arranged by gearing the rotors of the resolvers. The resultant individual currents are added in parallel. The value is read on a voltimeter and the phase is read on an oscilloscope. ODFAC cna perform the summation rapidly with an accuracy adequate for most purposes. The simplicity of design eliminates almost all electrical or mechanical failures. ODFAC can be used for double and triple summations by using standard trigonometric expansions.