A CONDENSER MEMORY UNIT FOR IMPROVING SIGNAL-TO-NOISE RATIOS

Abstract

The unit contains 30 low-leakage condensers which can store a signal for several hours if necessary. If the signal is repeated over and over, the successive scans can be added in and the signal-to-noise ratio builds up as the square root of the number of repetitions. In principle, the final signal-to-noise ratio is only slightly better than would be obtained from a single scan stretched out to fill the same total time, but in practice the result may be considerably better, especially if the signal fluctuates slowly. It has been used successfully in several investigations of twilight spectra with photoelectric and photoconductive spectrometers. The original version took 1 minute per scan and was rather bulky; a recent modification can scan 32 channels in 10 seconds if required.