3/51 4.2 Fundamental Standards ·Standard Levels International National Reference Standards 一 Working Standards Interlaboratory Standards Fundamental Quantities of the International Measuring System Length,Time,Mass,Temperature ·Length -Prior to 1960,platinum(铂，白金)-iridium(铱)international Meter Bar(米棒) From 1960,1650763.73 wavelength of krypton-86(-86)lamp in specified condition 中文课本中米的定义：1米是“光在真空中于1/299792458秒的时间间隔内 所经历路程的长度”，称为“米的国际基准”。 。Time In 1956,time interval definition,by the International Committee on Weights and Measures In 1964,frequencies of atomic resonators,by metrologists Cesium Notes:1.Intent is to show benchmarks Cesium 4/51 of progress.Various clock types atomic atomic (improved 10 can show improved accuracies. NBS HI) (NBS-5 EST) 2.Prior to 1000 A.D.varied timekeepers were used such Cesium 100 as mechanical water clocks atomic nocturnials,sundials,time (NBS I) 1 us candles,etc..of little known Cesium accuracy. 10 FIRST ATOMIC CL0CK(1949) Accuracy of 100 ephemeris time Quartz crystal 型 Variations in earth's rotation rate 44444464644446/4464444444444444 Pendulum free and FREE PENDULU (SHORTT) 10 pressure constant (Riefler) 台 100 Barometric Chronometer (Harrison) compensation Robinson】 1 Temperature compensation(Graham). ●improved escapement 10- Pendulum(Huygen) (Graham) 子 Cross-beat 102 escapement hydromechanical (Burgi) 103 1973 Verge and foliot 10 1 hr balance clocks 1000 1200 1400 1600 1800 2000 Calendar years,A.D.4.2 Fundamental Standards • Standard Levels – International – National Reference Standards – Working Standards – Interlaboratory Standards • Fundamental Quantities of the International Measuring System – Length, Time, Mass, Temperature • Length – Prior to 1960, platinum(铂, 白金)– iridium(铱) international Meter Bar(米棒) – From 1960, 1650763.73 wavelength of krypton-86(氪-86) lamp in specified condition – 中文课本中米的定义：1米是“光在真空中于1/299792458秒的时间间隔内 所经历路程的长度”，称为“米的国际基准”。 • Time – In 1956, time interval definition, by the International Committee on Weights and Measures – In 1964, frequencies of atomic resonators, by metrologists 3/51 苏颂及其水运仪象台 4.2 Fundamental Standards Figure 4.2 History of Time Keeping 4/51