Isolate Analyzing and Sourcing Errors
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Measurement of many fundamental quantities is made by comparing the Device Under Test (DUT) to a known reference. It is assumed that the reference quantity and the quantity being measured do not interact at a level that will compromise the measurement. However measurements that involve temporal quantities, such as frequency, do have an interaction at a level that is measureable. When two frequencies in a system are very close to each other, 10.000,000 MHz and 10.000,001 MHz for example, edges will become synchronous with each other at a rate proportional to the difference of the two frequencies. Edges of the frequency of interest going in and out of alignment result in measurement errors in these systems. For 10.000,000 MHz and 10.000,001 MHz, the rate at which the edges go in and out of alignment is 1 Hz. The difference of the two frequencies is known as the beat frequency. Minimizing the beat frequency effecting a measurement presents a design challenge to the design of frequency sources and frequency analyzers (counters).