New Frequency Counting Principle Improves Resolution; Conference paper

摘要

Frequency counters have gone through several evolutionary stages in their design since their first appearance on the market: Stage 1 until 1970's -- Conventional counting; Stage 2 through 1980's -- Reciprocal counting (period measurement + inversion); Stage 3 through 1990's -- Interpolating Reciprocal Counting; Stage 4 through 2000's -- Multiple Time Stamp Average Continuous Counting. This paper describes the theory and design of frequency counters, and analyses the improvements in the latest generation of frequency counters. The newly introduced high-resolution CNT-90 Timer/Counter/Analyzer from Pendulum Instruments AB in Sweden is used as a commercially available example of the latest design technology in this presentation. The advantages of continuous time-stamping technique are discussed, for example regression analysis, to reduce effects of measurement noise and to improve resolution to 12 digits of measuring time. Another example is the ability for seamless back-to-back measurements without missing any period, which is essential for theoretically correct calculation of Allan Deviation.