honor for OMICRON electronics and the CAL 542, and for OMICRON Calibrations, a small ISO/IEC 17025 accredited calibration laboratory, it presented a unique opportunity to participate in a ring comparison with various NMIs, albeit incognito. We conducted a detailed analysis of the CAL 542 and calibrated it before and after the intercomparison. The calibration reports to the left from VTT MIKES show the calibrator’s temperature stability drift over time. Reference Change in charge due to temperature (23.0 ± 2.0 °C) CAL 542 A 0.035% CAL 542 B 0.045% CAL 542 C 0.012% CAL 542 D –0.005% Temperature dependence of CAL 542: The highest temperature dependency we observed using the CAL 542 B calibrator was 0.045%/K, which is well within guaranteed tolerances of less than ±0.1% (for 23.0±2.0 °C). Traveling standards’ drift behavior over time Being able to remain this stable over time is even more amazing, as seen in an original statement from the preliminary report: “The measurements carried out at the pilot laboratory (VTT) before starting the comparison (Nov 2021), in the middle of the loops (Nov 2022), and at the end of the comparison (Aug 2023) were used to establish the standards’ drift behavior. The calibration history for an apparent charge is presented in the figures on the next page. Error bars present the calibration uncertainty at the end-comparison (Aug 2023). No significant drift was observed.” Temperature dependence of calibrator charge (CAL 542 A, B, C, D). Results are normalized to 23 °C / 73,4 °F. Temperature [°C] Temperature [°C] Charge difference B 10 15 20 25 30 35 0.4% 0.2% 0.0% –0.2% –0.4% –0.6% 0.6% 1 2 5 10 20 50 100 C 10 15 20 25 30 35 0.4% 0.2% 0.0% –0.2% –0.4% –0.6% 0.6% 10 20 50 100 200 500 1,000 D 10 15 20 25 30 35 0.4% 0.2% 0.0% –0.2% –0.4% –0.6% 0.6% 100 200 500 1,000 2,000 Nominal charge [pC] A 10 15 20 25 30 35 0.4% 0.2% 0.0% –0.2% –0.4% –0.6% 0.6% 0.1 0.2 0.5 1 2 5 10 A 10 15 20 25 30 35 0.4% 0.2% 0.0% –0.2% –0.4% –0.6% 0.6% 0.1 0.2 0.5 1 2 5 10 48
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