HP HP-Bench-Briefs-1990-01-03 free download

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SERVICE INFORMATION FROM HEWLETT-PACKARD 1 st Quarter 1990 e The 1990 Changes in National Reference Standards On January 1,1990, the U.S. National fined. Minor changes are being made Institute of Standards and Technol- to the standards of capacitance and ogy (NIST), and other national stan- mass maintained in some countries; dards organizations worldwide made however, the magnitude of these ad- important changes to the assigned justments, like the watt, is only of values of national reference standards academic interest to most users. in most countries of the world. Figure 1. The U.S. National Conference of In most countries, an increase in the Standards Laboratories (NCSL) sticker for volt of 8.1 parts per million (ppm) oc- indicatingequipment that is calibrated or Calibration and Traceability curred. In the U.S.A., the increase of adjusted to the new unit representations. 9.3 ppm and in France, 6.7 ppm. All Regular calibration assures that a values of dc and ac voltage were af- measuring instrument meets the fected equally in any one country. The user's expectation of performance, as ohm changed value in all countries, defined by the instrument's pub- except Australia, by different lished specifications. To ensure amounts - typically an increase of 1 HP 740A/B DC StandardDifferen- worldwide consistency, calibration to 2 ppm. All values of resistance are tial Voltmeter measurements are referenced (trace- equally affected. able) to common defining base units rn HP 2804A Quartz Thermometer in the International System of Units. with HP 18110A or HI' 18111A The IPTS-68 became the International Laboratory Probes Temperature Scale 1990. The change It is the task of the national standards is rather more complex than for the rn HP 2813B/C/D/E Quartz Pressure laboratories to maintain measure- electrical units. Both the magnitude Probes and Sets ment units as practical reference stan- and polarity of the changes vary rn HP 3235A Switchmest Unit with dards derived from the base unit defi- throughout the scale. HP 34520A/B 6 z Digit Multimeter Y nitions. However, experime