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Timing and coincidence circuitry for a time-sharing analog function generator Fiorentino, Joseph Samuel

Abstract

This thesis is concerned with the timing and coincidence circuitry which controls the operation of a time-sharing function generator and four-quadrant analog multiplier. The functions to be generated are fed into the computer in time sequence as voltage waveforms of short duration, A waveform is sampled at a particular value of the independent variable x and the resulting ordinate Ef is normalized with respect to the maximum function ordinate Em and multiplied by a reference voltage Er. The output of the multiplier is then a voltage which represents the expression EfEr/Em and this voltage is channeled through the computer. Multiplication is performed by the following method. Two voltages E₁ and E₂ are simultaneously applied to two identical linear networks whose response to unit voltage is N(t). The outputs are then E₁N(t) and E₂N(t). If, on comparing E₁N(t) with a reference voltage E₃, the second sweep E₂N(t) is clamped at the instant of equality, then N(t) = E₃/E₁ and the output is E = E₂N(t) = E₂E₃/E₁. The present proposal is to generate the functions optically. A function is graphed, photographed on 35 millimeter film, and mounted on the rim of a rotating disc. The optical system projects a narrow segment of the function onto a phototube and its output, biased for the zero level, follows the function ordinate in a strict voltage analog sense. The full abscissa scale is represented by a constant voltage and the input specifying the sampling point is some fraction of this full-scale voltage. In order that the sampling point x be independent of the velocity of the scanning disc the coincidence circuitry eliminates velocity as a variable in the selection of x.

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