Advancements in high-performance timing for long term underwater experiments: A comparison of chip scale atomic clocks to traditional microprocessor-compensated crystal oscillators

A. Gardner, J. Collins
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引用次数: 30

Abstract

We discuss the merits and performance of two commercially available time bases - a microprocessor-compensated crystal oscillator designed and manufactured by Seascan, Inc. of Falmouth, MA, and a chip-scale atomic clock (CSAC), designed and manufactured by Symmetricom, Inc. of San Jose, CA - for use in autonomous underwater instrumentation. Over the last ~10 years, the WHOI Ocean Bottom Seismology group has used the Seascan time base in its fleet of ~100 Ocean-Bottom Seismographs (OBS), and has acquired a record of Seascan performance amounting to over 183 cumulative seafloor years and over 25 years of cumulative test time in a temperature-chamber across 120 clocks. These data show that the Seascan clocks perform within their quoted specification in almost all cases, and if carefully selected can provide performance significantly exceeding their specifications, all at a very modest 5 mW of power consumption. Our testing has also shown some unexpected effects in certain units that may undermine timing quality if not understood and controlled. Within the last year or so, chip-scale atomic clocks have become available, and we have installed these time bases in 15 OBS. These CSACs offer two orders of magnitude improvement in precision, at the cost of significantly greater power consumption (~120 mW). We have deployed thirteen instruments on the ocean floor for a 6-month experiment using CSACs as the time base. In addition we have tested 4 more units in the lab. Based on the performance that we have seen in the field and in the lab, both time bases are worthy of consideration in new ocean instrumentation. As expected, the CSACs show better stability, lower aging, and better temperature response, at the expense of higher power consumption. This paper will present a detailed comparison of both clocks, showing the tradeoffs that need to be considered when selecting a time base. We will also look at techniques available to improve the aggregate performance of the Seascan time bases to well above their nominal specifications.
长期水下实验中高性能定时的进展:芯片级原子钟与传统微处理器补偿晶体振荡器的比较
我们讨论了两种商用时基的优点和性能——一种是由马萨诸塞州法尔茅斯的Seascan公司设计和制造的微处理器补偿晶体振荡器,另一种是由加利福尼亚州圣何塞的Symmetricom公司设计和制造的芯片级原子钟(CSAC),用于自主水下仪器。在过去的10年里,WHOI海底地震学小组在其约100台海底地震仪(OBS)的船队中使用了Seascan时间基础,并获得了超过183年累积海底年的Seascan性能记录,以及超过25年在120个时钟的温度室中的累积测试时间。这些数据表明,在几乎所有情况下,Seascan时钟的性能都在其引用的规格范围内,如果仔细选择,可以提供显着超过其规格的性能,所有这些都在非常适度的5兆瓦功耗下。我们的测试也显示了一些意想不到的影响,在某些单位,可能会破坏计时质量,如果不理解和控制。在去年左右,芯片级原子钟已经可用,我们已经在15个OBS中安装了这些时间基础。这些csac在精度上提供了两个数量级的提高,但代价是更大的功耗(~120 mW)。我们在海底部署了13台仪器,以CSACs为时间基础进行为期6个月的实验。另外,我们在实验室又测试了4个单元。根据我们在现场和实验室中所看到的性能,这两种时间基都值得在新的海洋仪器中考虑。正如预期的那样,csac表现出更好的稳定性、更低的老化和更好的温度响应,但代价是更高的功耗。本文将对这两种时钟进行详细的比较,展示在选择时间基础时需要考虑的权衡。我们还将研究可用的技术,以提高Seascan时基的总性能,使其远远超过其标称规格。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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