490:
478:
450:
called a limited calibration. But if the final measurement requires 10% accuracy, then the 3% gauge never can be better than 3.3:1. Then perhaps adjusting the calibration tolerance for the gauge would be a better solution. If the calibration is performed at 100 units, the 1% standard would actually be anywhere between 99 and 101 units. The acceptable values of calibrations where the test equipment is at the 4:1 ratio would be 96 to 104 units, inclusive. Changing the acceptable range to 97 to 103 units would remove the potential contribution of all of the standards and preserve a 3.3:1 ratio. Continuing, a further change to the acceptable range to 98 to 102 restores more than a 4:1 final ratio.
810:
801:
120:(BIPM) is the following: "Operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties (of the calibrated instrument or secondary standard) and, in a second step, uses this information to establish a relation for obtaining a measurement result from an indication."
685:
442:
uncertainty of all of the standards involved is considered to be insignificant when the final measurement is also made with the 4:1 ratio. This ratio was probably first formalized in
Handbook 52 that accompanied MIL-STD-45662A, an early US Department of Defense metrology program specification. It was 10:1 from its inception in the 1950s until the 1970s, when advancing technology made 10:1 impossible for most electronic measurements.
710:, i.e. they had the same units as the quantity being measured. Examples include length using a yardstick and mass using a weighing scale. At the beginning of the twelfth century, during the reign of Henry I (1100-1135), it was decreed that a yard be "the distance from the tip of the King's nose to the end of his outstretched thumb." However, it wasn't until the reign of Richard I (1197) that we find documented evidence.
590:
378:" when used within the stated environmental conditions over some reasonable period of time. Having a design with these characteristics increases the likelihood of the actual measuring instruments performing as expected. Basically, the purpose of calibration is for maintaining the quality of measurement as well as to ensure the proper working of particular instrument.
744:
529:. These procedures capture all of the steps needed to perform a successful calibration. The manufacturer may provide one or the organization may prepare one that also captures all of the organization's other requirements. There are clearinghouses for calibration procedures such as the Government-Industry Data Exchange Program (GIDEP) in the United States.
598:
the instrument. There also are labels showing the date of the last calibration and when the calibration interval dictates when the next one is needed. Some organizations also assign unique identification to each instrument to standardize the record keeping and keep track of accessories that are integral to a specific calibration condition.
825:
would be the calibration standard. For measurement of indirect quantities of pressure per unit area, the calibration uncertainty would be dependent on the density of the manometer fluid, and the means of measuring the height difference. From this other units such as pounds per square inch could be inferred and marked on the scale.
387:
organization generally assigns the actual calibration interval, which is dependent on this specific measuring equipment's likely usage level. The assignment of calibration intervals can be a formal process based on the results of previous calibrations. The standards themselves are not clear on recommended CI values:
430:"... shall be calibrated at periodic intervals established and maintained to assure acceptable accuracy and reliability...Intervals shall be shortened or may be lengthened, by the contractor, when the results of previous calibrations indicate that such action is appropriate to maintain acceptable reliability."
558:
More commonly, a calibration technician is entrusted with the entire process and signs the calibration certificate, which documents the completion of a successful calibration. The basic process outlined above is a difficult and expensive challenge. The cost for ordinary equipment support is generally
461:
Also in the example above, ideally the calibration value of 100 units would be the best point in the gauge's range to perform a single-point calibration. It may be the manufacturer's recommendation or it may be the way similar devices are already being calibrated. Multiple point calibrations are also
135:
The increasing need for known accuracy and uncertainty and the need to have consistent and comparable standards internationally has led to the establishment of national laboratories. In many countries a
National Metrology Institute (NMI) will exist which will maintain primary standards of measurement
485:
As an example, a manual process may be used for calibration of a pressure gauge. The procedure requires multiple steps, to connect the gauge under test to a reference master gauge and an adjustable pressure source, to apply fluid pressure to both reference and test gauges at definite points over the
597:
To prevent unauthorized access to an instrument tamper-proof seals are usually applied after calibration. The picture of the oscilloscope rack shows these, and prove that the instrument has not been removed since it was last calibrated as they will possible unauthorized to the adjusting elements of
359:
at specific points on the scale. This is the perception of the instrument's end-user. However, very few instruments can be adjusted to exactly match the standards they are compared to. For the vast majority of calibrations, the calibration process is actually the comparison of an unknown to a known
441:
The next step is defining the calibration process. The selection of a standard or standards is the most visible part of the calibration process. Ideally, the standard has less than 1/4 of the measurement uncertainty of the device being calibrated. When this goal is met, the accumulated measurement
449:
For example, a gauge with 3% manufacturer-stated accuracy can be changed to 4% so that a 1% accuracy standard can be used at 4:1. If the gauge is used in an application requiring 16% accuracy, having the gauge accuracy reduced to 4% will not affect the accuracy of the final measurements. This is
223:
To communicate the quality of a calibration the calibration value is often accompanied by a traceable uncertainty statement to a stated confidence level. This is evaluated through careful uncertainty analysis. Some times a DFS (Departure From Spec) is required to operate machinery in a degraded
824:
In the front and back views of a
Bourdon gauge on the right, applied pressure at the bottom fitting reduces the curl on the flattened pipe proportionally to pressure. This moves the free end of the tube which is linked to the pointer. The instrument would be calibrated against a manometer, which
783:
saw the adoption of "indirect" pressure measuring devices, which were more practical than the manometer. An example is in high pressure (up to 50 psi) steam engines, where mercury was used to reduce the scale length to about 60 inches, but such a manometer was expensive and prone to damage. This
445:
Maintaining a 4:1 accuracy ratio with modern equipment is difficult. The test equipment being calibrated can be just as accurate as the working standard. If the accuracy ratio is less than 4:1, then the calibration tolerance can be reduced to compensate. When 1:1 is reached, only an exact match
581:
The 'single measurement' device used in the basic calibration process description above does exist. But, depending on the organization, the majority of the devices that need calibration can have several ranges and many functionalities in a single instrument. A good example is a common modern
386:
The exact mechanism for assigning tolerance values varies by country and as per the industry type. The measuring of equipment is manufacturer generally assigns the measurement tolerance, suggests a calibration interval (CI) and specifies the environmental range of use and storage. The using
172:
and many others. Since the Mutual
Recognition Agreement was signed it is now straightforward to take traceability from any participating NMI and it is no longer necessary for a company to obtain traceability for measurements from the NMI of the country in which it is situated, such as the
465:
There may be specific connection techniques between the standard and the device being calibrated that may influence the calibration. For example, in electronic calibrations involving analog phenomena, the impedance of the cable connections can directly influence the result.
462:
used. Depending on the device, a zero unit state, the absence of the phenomenon being measured, may also be a calibration point. Or zero may be resettable by the user-there are several variations possible. Again, the points to use during calibration should be recorded.
373:
The calibration process begins with the design of the measuring instrument that needs to be calibrated. The design has to be able to "hold a calibration" through its calibration interval. In other words, the design has to be capable of measurements that are "within
486:
span of the gauge, and to compare the readings of the two. The gauge under test may be adjusted to ensure its zero point and response to pressure comply as closely as possible to the intended accuracy. Each step of the process requires manual record keeping.
550:
After all of this, individual instruments of the specific type discussed above can finally be calibrated. The process generally begins with a basic damage check. Some organizations such as nuclear power plants collect "as-found" calibration data before any
185:
To improve the quality of the calibration and have the results accepted by outside organizations it is desirable for the calibration and subsequent measurements to be "traceable" to the internationally defined measurement units. Establishing
771:
pushes the liquid down the right side of the manometer U-tube, while a length scale next to the tube measures the difference of levels. The resulting height difference "H" is a direct measurement of the pressure or vacuum with respect to
147:
The NMI supports the metrological infrastructure in that country (and often others) by establishing an unbroken chain, from the top level of standards to an instrument used for measurement. Examples of
National Metrology Institutes are
763:
were designed. All these would have linear calibrations using gravimetric principles, where the difference in levels was proportional to pressure. The normal units of measure would be the convenient inches of mercury or water.
398:"A calibration certificate (or calibration label) shall not contain any recommendation on the calibration interval except where this has been agreed with the customer. This requirement may be superseded by legal regulations.”
453:
This is a simplified example. The mathematics of the example can be challenged. It is important that whatever thinking guided this process in an actual calibration be recorded and accessible. Informality contributes to
446:
between the standard and the device being calibrated is a completely correct calibration. Another common method for dealing with this capability mismatch is to reduce the accuracy of the device being calibrated.
489:
291:). The standard instrument for each test device varies accordingly, e.g., a dead weight tester for pressure gauge calibration and a dry block temperature tester for temperature gauge calibration.
1101:
651:, with excavations revealing the use of angular gradations for construction. The term "calibration" was likely first associated with the precise division of linear distance and angles using a
1013:
702:
ounce calibration error at zero. This is a "zeroing error" which is inherently indicated, and can normally be adjusted by the user, but may be due to the string and rubber band in this case
232:
663:. These two forms of measurement alone and their direct derivatives supported nearly all commerce and technology development from the earliest civilizations until about AD 1800.
1270:
1075:. Aiken, SC: NCSL International Workshop and Symposium, under contract with the Office of Scientific and Technical Information, U.S. Department of Energy. pp. 1–2.
586:. There easily could be 200,000 combinations of settings to completely calibrate and limitations on how much of an all-inclusive calibration can be automated.
601:
When the instruments being calibrated are integrated with computers, the integrated computer programs and any calibration corrections are also under control.
477:
1105:
227:
Measuring devices and instruments are categorized according to the physical quantities they are designed to measure. These vary internationally, e.g.,
1017:
76:
of known accuracy. Such a standard could be another measurement device of known accuracy, a device generating the quantity to be measured such as a
930:
752:
228:
224:
state. Whenever this does happen, it must be in writing and authorized by a manager with the technical assistance of a calibration technician.
497:
An automatic pressure calibrator is a device that combines an electronic control unit, a pressure intensifier used to compress a gas such as
347:
the output or indication on a measurement instrument to agree with value of the applied standard, within a specified accuracy. For example, a
536:
and/or natural physical constants, the measurement standards with the least uncertainty in the laboratory, are reached. This establishes the
174:
555:
is performed. After routine maintenance and deficiencies detected during calibration are addressed, an "as-left" calibration is performed.
420:"Where necessary to ensure valid results, measuring equipment shall...be calibrated or verified at specified intervals, or prior to use...”
117:
1245:
481:
Manual calibration - US serviceman calibrating a pressure gauge. The device under test is on his left and the test standard on his right.
887:
1430:
636:
202:. This may be done by national standards laboratories operated by the government or by private firms offering metrology services.
1211:
1016:. Fluid Control Research Institute (FCRI), Ministry of Heavy Industries & Public Enterprises, Govt. of India. Archived from
41:
This article is about assessing the accuracy of a measurement device, like a scale or a ruler. For the statistical concept, see
1042:
Quality
Control Training Manual: Comprehensive Training Guide for API, Finished Pharmaceutical and Biotechnologies Laboratories
1277:
1477:
1392:
1365:
1338:
1179:
1050:
973:
165:
1076:
105:
Strictly speaking, the term "calibration" means just the act of comparison and does not include any subsequent adjustment.
408:"...shall be calibrated or verified at periodic intervals established and maintained to assure acceptable reliability..."
517:. An automatic system may also include data collection facilities to automate the gathering of data for record keeping.
871:
1530:
1502:
336:
whenever observations appear questionable or instrument indications do not match the output of surrogate instruments
149:
1354:
Franceschini, Fiorenzo; Galetto, Maurizio; Maisano, Domenico; Mastrogiacomo, Luca; Pralio, Barbara (6 June 2011).
1546:
776:. In the absence of differential pressure both levels would be equal, and this would be used as the zero point.
108:
The calibration standard is normally traceable to a national or international standard held by a metrology body.
962:
ISO 17025: "General requirements for the competence of testing and calibration laboratories" (2005), section 5.
1127:
533:
199:
137:
235:-141 in India. Together, these standards cover instruments that measure various physical quantities such as
564:
514:
352:
220:
standards require that these traceable actions are to a high level and set out how they can be quantified.
123:
This definition states that the calibration process is purely a comparison, but introduces the concept of
351:
could be calibrated so the error of indication or the correction is determined, and adjusted (e.g. via
17:
648:
236:
205:
927:
339:
as specified by a requirement, e.g., customer specification, instrument manufacturer recommendation.
845:
679:
42:
35:
1415:
212:
system which includes formal, periodic, and documented calibration of all measuring instruments.
876:
124:
1236:
906:
610:
328:, or physical damage, which might potentially have compromised the integrity of its calibration
1467:
1382:
1355:
1162:
Ligowski, M.; Jabłoński, Ryszard; Tabe, M. (2011), Jabłoński, Ryszard; Březina, Tomaš (eds.),
719:"Throughout the realm there shall be the same yard of the same size and it should be of iron."
1328:
1040:
780:
506:
375:
728:
1556:
773:
191:
73:
818:
Indirect reading design showing a
Bourdon tube from the front (left) and the rear (right).
525:
All of the information above is collected in a calibration procedure, which is a specific
8:
1409:
840:
552:
502:
288:
46:
1441:
1104:. The National Conference of Standards Laboratories (NCSL) International. Archived from
532:
This exact process is repeated for each of the standards used until transfer standards,
414:
1561:
1551:
884:– tuning, in music, means calibrating musical instruments into playing the right pitch.
625:
260:
1202:
1526:
1498:
1473:
1388:
1361:
1334:
1330:
The
Science of Empire: Scientific Knowledge, Civilization, and Colonial Rule in India
1185:
1175:
1046:
860:
850:
835:
756:
568:
248:
69:
789:
767:
In the direct reading hydrostatic manometer design on the right, applied pressure P
1302:
1167:
988:
854:
621:
559:
about 10% of the original purchase price on a yearly basis, as a commonly accepted
455:
1067:
934:
652:
510:
280:
252:
31:
1014:"Metrology, Pressure, Thermal & Eletrotechnical Measurement and Calibration"
493:
Automatic calibration - A U.S. serviceman using a 3666C auto pressure calibrator
892:
881:
689:
660:
639:
and calibration seem to have been created between the ancient civilizations of
575:
276:
264:
256:
1171:
547:
for other factors that are considered during calibration process development.
1540:
1384:
Foundation: The
History of England from Its Earliest Beginnings to the Tudors
732:
640:
560:
392:
161:
1166:, Mechatronics: Recent Technological and Scientific Advances, p. 227,
1133:. Washington, DC: U.S. Department of Defense. 1 August 1998. Archived from
900:
785:
583:
537:
272:
187:
141:
1244:. U.S. Department of the Interior, Bureau of Reclamation. pp. 70–73.
950:
ISO 9001: "Quality management systems — Requirements" (2008), section 7.6.
343:
In general use, calibration is often regarded as including the process of
30:"Zeroing" redirects here. For the U.S. government antidumping duties, see
896:
784:
stimulated the development of indirect reading instruments, of which the
724:
644:
526:
348:
284:
268:
65:
53:
1353:
974:"Calibration Laboratories: Technical Guide for Mechanical Measurements"
194:
which is directly or indirectly related to national standards (such as
1134:
127:
in relating the accuracies of the device under test and the standard.
760:
684:
629:
544:
325:
217:
209:
57:
666:
632:, thought to be derived from a measurement of the calibre of a gun.
809:
498:
474:
Calibration methods for modern devices can be manual or automatic.
240:
213:
1189:
91:
The outcome of the comparison can result in one of the following:
1466:
Fridman, A. E.; Sabak, Andrew; Makinen, Paul (23 November 2011).
865:
356:
169:
77:
1204:
Military
Handbook: Evaluation of Contractor's Calibration System
738:
1497:. London: The Institute of Measurement and Control. p. 5.
800:
140:
plus a number of derived units) which will be used to provide
101:
an adjustment made to correct the error to an acceptable level
572:
244:
85:
81:
589:
1360:. Springer Science & Business Media. pp. 117–118.
1357:
Distributed Large-Scale Dimensional Metrology: New Insights
984:
656:
458:
and other difficult to diagnose post calibration problems.
195:
157:
1039:
Haider, Syed Imtiaz; Asif, Syed Erfan (16 February 2011).
972:
Faison, C. Douglas; Brickenkamp, Carroll S. (March 2004).
1472:. Springer Science & Business Media. pp. 10–11.
1210:. U.S. Department of Defense. 17 August 1984. p. 7.
751:
One of the earliest pressure measurement devices was the
95:
no significant error being noted on the device under test
743:
520:
1347:
1164:
Procedure for Calibrating Kelvin Probe Force Microscope
1157:
1155:
938:— Basic and general concepts and associated terms (VIM)
299:
Calibration may be required for the following reasons:
153:
1271:"KNC Model 3666 Automatic Pressure Calibration System"
1128:"Calibration Systems Requirements (Military Standard)"
98:
a significant error being noted but no adjustment made
1469:
The Quality of Measurements: A Metrological Reference
1238:
Procedure for calibrating pressure gauges (USBR 1040)
1161:
723:
Other standardization attempts followed, such as the
1408:
Bland, Alfred Edward; Tawney, Richard Henry (1919).
1152:
620:
The words "calibrate" and "calibration" entered the
469:
355:
constants) so that it shows the true temperature in
315:
when a specified usage (operating hours) has elapsed
1465:
1422:
928:
JCGM 200:2008 International vocabulary of metrology
436:
971:
324:after an instrument has been exposed to a shock,
306:after an instrument has been repaired or modified
294:
1538:
1521:Crouch, Stanley & Skoog, Douglas A. (2007).
1459:
1495:Guide to the Measurement of Pressure and Vacuum
1401:
593:An instrument rack with tamper-indicating seals
130:
1486:
920:
755:(1643), which read atmospheric pressure using
1032:
739:The early calibration of pressure instruments
578:devices can be even more costly to maintain.
283:), and, thermodynamic or thermal properties (
1276:. King Nutronics Corporation. Archived from
363:
309:moving from one location to another location
190:is accomplished by a formal comparison to a
118:International Bureau of Weights and Measures
116:The formal definition of calibration by the
27:Check on the accuracy of measurement devices
1407:
1374:
747:Direct reading design of a U-tube manometer
1411:English Economic History: Select Documents
1038:
958:
956:
888:Precision measurement equipment laboratory
318:before and/or after a critical measurement
144:to customer's instruments by calibration.
1320:
946:
944:
753:Mercury barometer, credited to Torricelli
731:from France and the establishment of the
604:
198:in the USA), international standards, or
180:
1387:. St. Martin's Press. pp. 133–134.
1069:Simplified Calibration Interval Analysis
742:
683:
588:
488:
476:
312:when a specified time period has elapsed
84:tone, or a physical artifact, such as a
1428:
1380:
953:
14:
1539:
941:
727:(1225) for liquid measures, until the
667:Calibration of weights and distances (
1492:
1326:
655:and the measurement of gravitational
637:earliest known systems of measurement
521:Process description and documentation
1065:
368:
1523:Principles of Instrumental Analysis
505:used to detect desired levels in a
24:
1431:"Pressure and vacuum measurements"
1381:Ackroyd, Peter (16 October 2012).
872:Measurement Microphone Calibration
111:
25:
1573:
470:Manual and automatic calibrations
808:
799:
45:. For the geometry concept, see
1295:
1263:
1251:from the original on 2013-05-12
1229:
1217:from the original on 2014-12-04
1195:
1102:"ANSI/NCSL Z540.3-2006 (R2013)"
1082:from the original on 2007-04-18
706:Early measurement devices were
437:Standards required and accuracy
1525:. Pacific Grove: Brooks Cole.
1414:. Macmillan Company. pp.
1333:. SUNY Press. pp. 23–24.
1120:
1094:
1059:
1006:
965:
295:Instrument calibration prompts
13:
1:
1438:Physical Methods of Chemistry
1303:"the definition of calibrate"
913:
895:– a device used to calibrate
668:
565:scanning electron microscopes
534:certified reference materials
200:certified reference materials
868:Association of European NMIs
381:
321:after an event, for example
175:National Physical Laboratory
131:Modern calibration processes
7:
1429:Tilford, Charles R (1992).
828:
759:. Soon after, water-filled
360:and recording the results.
10:
1578:
1515:
677:
615:
608:
509:, and accessories such as
271:), mechanical quantities (
206:Quality management systems
40:
29:
1440:: 106–173. Archived from
1172:10.1007/978-3-642-23244-2
1045:. CRC Press. p. 49.
563:. Exotic devices such as
364:Basic calibration process
331:sudden changes in weather
237:electromagnetic radiation
1493:CuscĂł, Laurence (1998).
846:Calibration (statistics)
680:Weights and Measures Act
43:Calibration (statistics)
36:Zeroing (disambiguation)
877:Measurement uncertainty
792:is a notable example.
255:), time and frequency (
231:150-2G in the U.S. and
125:measurement uncertainty
1547:Accuracy and precision
1327:Baber, Zaheer (1996).
907:Systems of measurement
853:– used to calibrate a
748:
703:
611:History of measurement
605:Historical development
594:
494:
482:
289:temperature controller
208:call for an effective
181:Quality of calibration
68:values delivered by a
34:. For other uses, see
781:Industrial Revolution
746:
687:
628:, in descriptions of
592:
507:hydraulic accumulator
492:
480:
376:engineering tolerance
64:is the comparison of
1066:Bare, Allen (2006).
981:NIST Handbook 150-2G
774:atmospheric pressure
540:of the calibration.
74:calibration standard
841:Calibrated geometry
624:as recently as the
553:routine maintenance
503:pressure transducer
47:Calibrated geometry
933:2019-10-31 at the
749:
729:Mètre des Archives
715:Assize of Measures
704:
626:American Civil War
595:
495:
483:
261:ionizing radiation
1479:978-1-4614-1478-0
1394:978-1-250-01367-5
1367:978-0-85729-543-9
1340:978-0-7914-2919-8
1181:978-3-642-23244-2
1052:978-1-4398-4994-1
861:Deadweight tester
851:Color calibration
836:Calibration curve
569:gas chromatograph
369:Purpose and scope
249:sound level meter
70:device under test
16:(Redirected from
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1509:
1508:
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1003:
1001:
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993:
987:. Archived from
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969:
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948:
939:
924:
855:computer monitor
812:
803:
701:
700:
696:
688:An example of a
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670:
622:English language
456:tolerance stacks
303:a new instrument
72:with those of a
21:
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1020:on 14 June 2015
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1011:
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991:
976:
970:
966:
961:
954:
949:
942:
935:Wayback Machine
925:
921:
916:
911:
897:weighing scales
831:
822:
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439:
384:
371:
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297:
281:pressure switch
253:noise dosimeter
183:
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112:BIPM Definition
56:technology and
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32:Zeroing (trade)
28:
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22:
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609:Main article:
606:
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277:pressure gauge
265:Geiger counter
257:intervalometer
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733:Metric system
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691:
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561:rule-of-thumb
556:
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162:United States
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1557:Measurement
1451:28 November
1287:28 November
1255:28 November
1221:28 November
1144:28 November
1112:28 November
1086:28 November
899:that weigh
857:or display.
725:Magna Carta
645:Mesopotamia
527:test method
353:calibration
349:thermometer
285:thermometer
269:light meter
177:in the UK.
66:measurement
62:calibration
54:measurement
1541:Categories
1190:2011935381
914:References
761:manometers
678:See also:
513:and gauge
267:), light (
136:(the main
18:Calibrated
1562:Metrology
1552:Standards
630:artillery
545:Metrology
393:ISO 17025
382:Frequency
345:adjusting
326:vibration
241:RF probes
218:ISO 17025
210:metrology
58:metrology
1312:18 March
1246:Archived
1212:Archived
1077:Archived
931:Archived
829:See also
659:using a
647:and the
515:fittings
499:Nitrogen
415:ISO-9001
214:ISO 9000
192:standard
138:SI units
1516:Sources
1024:14 June
998:14 June
866:EURAMET
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616:Origins
357:Celsius
170:Germany
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152:in the
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641:Egypt
573:laser
245:sound
86:meter
82:sound
1527:ISBN
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1453:2014
1389:ISBN
1362:ISBN
1335:ISBN
1314:2018
1289:2014
1257:2014
1223:2014
1186:LCCN
1176:ISBN
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1088:2014
1047:ISBN
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779:The
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543:See
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229:NIST
216:and
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