Digital techniques applied to sine test control

Digital techniques are applied to solve problems experienced in analogue circuitry, enabling the design of a highly reliable sine control system. A sine wave is generated whose frequency is proportional to a digital number, held in the counters of the sweep generator, using the frequency related pulse stream. This pulse stream is used to generate a ramp by applying it to a count. The rate of rise is varied by using a rate multiplier arranged to slow the pulse stream as the ramp proceeds. Variation of frequency depends only on the frequency of the pulse stream entering the circuit, and the oscillator runs quite acceptably at 0.1 Hz and 10 kHz. The total distortion at this stage is less than 2%. Since the control signal is quantized, only discrete changes in control are experienced, and the control lines are static most of the time; the digital system can reduce the effects of a noisy return signal by as much as 64 times. The greatest advantage of digital techniques is its use in integrator stabilization. A tracking capacitor ensures that conversion is done to an accuracy of 1%, and residual ripple on the output is removed by a low pass filter.