Abstract: The present disclosure provides an acquisition system for oscilloscopes having n input channels. The acquisition system comprises n A/D converters (2.1, 2.2, . . . , 2.n) with each of the n A/D converters receiving a signal under test from one of n channels and digitizing the received signal into digital samples; an acquisition memory for storing the digitized samples from the n A/D converters; and a memory allocation processor for dynamically allocating memory lengths (or memory depths) for the selected n input channels within an acquisition memory based on the user setting from the oscilloscope. To efficiently use the acquisition memory, the acquisition system does not allocate any memory areas for the input channels that are not selected. In addition, the acquisition system can set up sampling rates for the n input channels based on the frequencies of the signals under test received from the n input channels.