Table 6. Measurements of the duration of the TAI scale interval (File available on ftp://ftp2.bipm.org/pub/tai/scale/UTAI/utai16.ar) TAI is a realization of coordinate time TT. The following tables give the fractional deviation d of the scale interval of TAI from that of TT (in practice the SI second on the geoid), i.e. the fractional frequency deviation of TAI with the opposite sign: d = -yTAI. In Table 6A, d is obtained on the given periods of estimation by comparison of the TAI frequency with that of the individual primary frequency standards (PFS) IT-CsF2, NIM5, NIST-F1, PTB-CS1, PTB-CS2, PTB-CSF1, PTB-CSF2, SU-CsFO2 and SYRTE-FO2 reported on the year 2016. In Table 6B, d is obtained on the given periods of estimation by comparison of the TAI frequency with that of the individual secondary frequency standard (SFS) SYRTE-FORb reported on the year 2016. Previous calibrations are available in the successive annual reports of the BIPM Time Section volumes 1 to 18 and in the BIPM Annual Report on Time Activities volumes 1 to 10 (web only since volume 4 for 2009). Each comparison is provided with the following information: uA is the uncertainty originating in the instability of the PFS, uB is the combined uncertainty from systematic effects, ulink/lab is the uncertainty in the link between the PFS and the clock participating to TAI, including the uncertainty due to dead-time, ulink/TAI is the uncertainty in the link to TAI, computed using the standard uncertainty of [UTC-UTC(k)], u is the quadratic sum of all four uncertainty values. In addition, Table 6B includes the following information: uSRep is the recommended uncertainty of the secondary representation of the second, as specified in the CIPM Recommendation identified under Ref(uS). In these tables, a frequency over a time interval is defined as the ratio of the end-point phase difference to the duration of the interval. The typical characteristics of the calibrations of the TAI frequency provided by the different primary and secondary standards reported in 2016 are indicated below. Reports of individual evaluations may be found at ftp://ftp2.bipm.org/pub/tai/data/PFS_reports. Ref(uB) is a reference giving information on the value of uB as stated in the 2015 reports, uB(Ref) is the uB value stated in this reference. Note that the current uB values are generally not the same as the peer reviewed values given in Ref(uB). Primary Type Type B std. uB(Ref) Ref(uB) Comparison Number/typical Standard /selection uncert/10-15 /10-15 with duration of comp. IT-CsF2 Fountain (0.17 to 0.48) 0.18 [1] H maser 7 / 10 d to 35 d NIM5 Fountain 1.4 1.4 [2] H maser 4 / 20 d to 20 d NIST-F1 Fountain 0.31 0.35 [3] H maser 1 / 20 d PTB-CS1 Beam /Mag. 8 8. [4] TAI 12 / 30 d to 35 d PTB-CS2 Beam /Mag. 12 12. [5] TAI 12 / 30 d to 35 d PTB-CSF1 Fountain 0.7 then (0.35-0.37) 1.4 [6] H maser 6 / 15 d to 35 d PTB-CSF2 Fountain (0.20 to 0.22) 0.41 [7] H maser 10 / 10 d to 30 d SU-CsFO2 Fountain 0.25 0.50 [8] H maser 4 / 15 d to 30 d SYRTE-FO2 Fountain (0.25 to 0.35) 0.23 [9] H maser 12 / 10 d to 30 d Secondary Type Type B std. uB(Ref) Ref(uB) Comparison Number/typical Standard uncert/10-15 /10-15 with duration of comp. SYRTE-FORb Fountain (0.28 to 0.35) 0.32 [10] H maser 13 / 10 d to 35 d More detailed information on the characteristics and operation of individual PFS and SFS may be found in the annexes supplied by the individual laboratories. Table 6A. Measurements of the duration of the TAI scale interval by Primary Frequency Standards Standard Period of d/10-15 uA/10-15 uB/10-15 ulink/lab ulink/TAI u/10-15 Note estimation /10-15 /10-15 IT-CsF2 57404 57414 -0.23 0.61 0.17 0.10 0.53 0.83 IT-CsF2 57414 57444 -0.87 0.45 0.17 0.13 0.20 0.54 IT-CsF2 57444 57474 -0.62 0.34 0.17 0.13 0.20 0.45 IT-CsF2 57474 57499 -1.13 0.34 0.17 0.14 0.23 0.47 IT-CsF2 57504 57539 -0.94 0.31 0.48 0.10 0.17 0.60 IT-CsF2 57639 57659 -0.60 0.34 0.17 0.22 0.28 0.52 IT-CsF2 57659 57689 -0.80 0.43 0.17 0.22 0.20 0.55 NIM5 57459 57479 -1.05 0.80 1.40 0.20 0.66 1.75 NIM5 57604 57629 -0.53 0.50 1.40 0.20 0.23 1.52 NIM5 57634 57654 0.68 0.50 1.40 0.20 0.28 1.53 NIM5 57664 57684 -0.94 0.60 1.40 0.20 0.28 1.56 NIST-F1 57419 57439 0.06 0.23 0.31 0.20 0.28 0.52 PTB-CS1 57384 57414 -12.55 6.00 8.00 0.00 0.07 10.00 (1) PTB-CS1 57414 57444 -14.41 6.00 8.00 0.00 0.07 10.00 PTB-CS1 57444 57474 -2.14 6.00 8.00 0.00 0.07 10.00 PTB-CS1 57474 57504 -7.35 6.00 8.00 0.00 0.07 10.00 PTB-CS1 57504 57539 -6.46 6.00 8.00 0.00 0.06 10.00 PTB-CS1 57539 57569 -8.04 6.00 8.00 0.00 0.07 10.00 PTB-CS1 57569 57599 -6.61 6.00 8.00 0.00 0.07 10.00 PTB-CS1 57599 57629 -7.42 6.00 8.00 0.00 0.07 10.00 PTB-CS1 57629 57659 -14.21 6.00 8.00 0.00 0.10 10.00 PTB-CS1 57659 57689 -20.97 6.00 8.00 0.00 0.13 10.00 PTB-CS1 57689 57719 -9.16 6.00 8.00 0.00 0.13 10.00 PTB-CS1 57719 57749 -21.05 6.00 8.00 0.00 0.13 10.00 PTB-CS2 57384 57414 0.68 3.00 12.00 0.00 0.07 12.37 (1) PTB-CS2 57414 57444 -2.22 3.00 12.00 0.00 0.07 12.37 PTB-CS2 57444 57474 -1.02 3.00 12.00 0.00 0.07 12.37 PTB-CS2 57474 57504 -8.54 3.00 12.00 0.00 0.07 12.37 PTB-CS2 57504 57539 -5.37 3.00 12.00 0.00 0.06 12.37 PTB-CS2 57539 57569 -9.51 3.00 12.00 0.00 0.07 12.37 PTB-CS2 57569 57599 -6.03 3.00 12.00 0.00 0.07 12.37 PTB-CS2 57599 57629 -4.95 3.00 12.00 0.00 0.07 12.37 PTB-CS2 57629 57659 -5.42 3.00 12.00 0.00 0.10 12.37 PTB-CS2 57659 57689 -8.74 3.00 12.00 0.00 0.13 12.37 PTB-CS2 57689 57719 -4.22 3.00 12.00 0.00 0.13 12.37 PTB-CS2 57719 57749 -4.42 3.00 12.00 0.00 0.13 12.37 PTB-CSF1 57369 57384 -0.25 0.10 0.70 0.01 0.12 0.72 PTB-CSF1 57384 57404 -0.46 0.09 0.70 0.02 0.09 0.71 PTB-CSF1 57474 57504 -1.02 0.08 0.37 0.08 0.07 0.39 PTB-CSF1 57564 57599 -0.40 0.06 0.35 0.05 0.06 0.36 PTB-CSF1 57599 57629 -0.41 0.08 0.35 0.10 0.07 0.38 PTB-CSF1 57699 57714 -1.95 0.12 0.35 0.05 0.24 0.45 PTB-CSF2 57379 57389 -0.52 0.21 0.22 0.07 0.18 0.36 PTB-CSF2 57459 57474 -1.21 0.15 0.20 0.02 0.12 0.28 PTB-CSF2 57474 57504 -1.38 0.12 0.20 0.13 0.07 0.27 PTB-CSF2 57539 57569 -0.58 0.12 0.20 0.04 0.07 0.25 PTB-CSF2 57579 57599 -0.75 0.12 0.20 0.02 0.09 0.25 PTB-CSF2 57599 57629 -0.89 0.13 0.20 0.07 0.07 0.26 PTB-CSF2 57634 57649 -0.88 0.13 0.20 0.03 0.24 0.34 PTB-CSF2 57659 57689 -1.51 0.13 0.20 0.04 0.13 0.27 PTB-CSF2 57699 57719 -1.54 0.26 0.20 0.07 0.19 0.38 PTB-CSF2 57719 57749 -1.40 0.12 0.20 0.04 0.13 0.27 SU-CsFO2 57384 57414 -0.05 0.27 0.25 0.11 0.59 0.70 SU-CsFO2 57444 57459 0.22 0.40 0.25 0.11 1.10 1.20 SU-CsFO2 57474 57504 0.49 0.40 0.25 0.11 0.59 0.76 SU-CsFO2 57509 57529 -0.75 0.27 0.25 0.11 0.85 0.93 Table 6A. (Cont.) Standard Period of d/10-15 uA/10-15 uB/10-15 ulink/lab ulink/TAI u/10-15 estimation /10-15 /10-15 SYRTE-FO2 57394 57414 -0.48 0.25 0.35 0.12 0.28 0.53 SYRTE-FO2 57414 57424 -0.23 0.33 0.34 0.10 0.53 0.72 SYRTE-FO2 57459 57474 -1.58 0.30 0.29 0.11 0.37 0.57 SYRTE-FO2 57474 57504 -1.09 0.35 0.26 0.10 0.20 0.49 SYRTE-FO2 57509 57539 -1.21 0.35 0.27 0.10 0.20 0.49 SYRTE-FO2 57539 57569 -0.19 0.20 0.27 0.10 0.20 0.40 SYRTE-FO2 57569 57599 -0.15 0.26 0.26 0.12 0.20 0.43 SYRTE-FO2 57599 57629 -0.86 0.20 0.25 0.10 0.20 0.39 SYRTE-FO2 57629 57659 -0.97 0.27 0.28 0.11 0.20 0.45 SYRTE-FO2 57689 57709 -1.71 0.25 0.29 0.12 0.28 0.49 SYRTE-FO2 57709 57719 -1.18 0.30 0.29 0.14 0.53 0.69 SYRTE-FO2 57719 57749 -1.12 0.30 0.34 0.11 0.20 0.51 Note: (1) Continuously operating as a clock participating in TAI. Table 6B. Measurements of the duration of the TAI scale interval by Secondary Frequency Standards Standard Period of d/10-15 uA/10-15 uB/10-15 ulink/lab ulink/TAI u/10-15 uSRep Ref(uS) estimation /10-15 /10-15 SYRTE-FORb 57389 57409 -0.22 0.20 0.35 0.11 0.28 0.50 1.3 [11] SYRTE-FORb 57414 57444 -0.28 0.25 0.29 0.11 0.20 0.44 1.3 [11] SYRTE-FORb 57444 57474 -0.16 0.20 0.28 0.13 0.20 0.42 0.7 [12] SYRTE-FORb 57474 57504 -0.50 0.30 0.28 0.10 0.20 0.47 0.7 [12] SYRTE-FORb 57504 57539 -0.23 0.20 0.28 0.10 0.17 0.40 0.7 [12] SYRTE-FORb 57539 57569 0.02 0.20 0.28 0.10 0.20 0.41 0.7 [12] SYRTE-FORb 57569 57599 -0.36 0.24 0.28 0.11 0.20 0.43 0.7 [12] SYRTE-FORb 57599 57629 -0.04 0.20 0.30 0.10 0.20 0.42 0.7 [12] SYRTE-FORb 57629 57659 -0.46 0.20 0.31 0.11 0.20 0.43 0.7 [12] SYRTE-FORb 57659 57689 -0.80 0.20 0.28 0.10 0.20 0.41 0.7 [12] SYRTE-FORb 57689 57709 -0.84 0.30 0.29 0.10 0.28 0.51 0.7 [12] SYRTE-FORb 57709 57719 -1.16 0.30 0.29 0.15 0.53 0.69 0.7 [12] SYRTE-FORb 57719 57749 -0.48 0.20 0.30 0.11 0.20 0.42 0.7 [12] References: [1] Levi F. et al., Metrologia 51, 270, 2014. 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