479:
467:
439:
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.
799:
790:
109:(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."
674:
431:
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.
699:, 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.
579:
367:" 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.
733:
518:. 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.
587:
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.
814:
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.
376:
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:
419:"... 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."
547:
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
450:
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
124:
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
474:
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
586:
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
348:
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
430:
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
438:
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
212:
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
813:
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
772:
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
434:
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
570:
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
375:
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
161:
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
454:
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.
451:
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.
362:
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
475:
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.
539:
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
174:
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
760:
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
136:
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
752:
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.
387:"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.”
442:
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
435:
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.
478:
280:). 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.
1090:
640:, 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
1002:
691:
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
221:
652:. 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.
1259:
1064:. 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.
575:. 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.
590:
When the instruments being calibrated are integrated with computers, the integrated computer programs and any calibration corrections are also under control.
466:
1094:
216:
Measuring devices and instruments are categorized according to the physical quantities they are designed to measure. These vary internationally, e.g.,
1006:
65:
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
919:
741:
217:
213:
state. Whenever this does happen, it must be in writing and authorized by a manager with the technical assistance of a calibration technician.
486:
An automatic pressure calibrator is a device that combines an electronic control unit, a pressure intensifier used to compress a gas such as
336:
the output or indication on a measurement instrument to agree with value of the applied standard, within a specified accuracy. For example, a
525:
and/or natural physical constants, the measurement standards with the least uncertainty in the laboratory, are reached. This establishes the
163:
544:
is performed. After routine maintenance and deficiencies detected during calibration are addressed, an "as-left" calibration is performed.
409:"Where necessary to ensure valid results, measuring equipment shall...be calibrated or verified at specified intervals, or prior to use...”
106:
1234:
470:
Manual calibration - US serviceman calibrating a pressure gauge. The device under test is on his left and the test standard on his right.
876:
1419:
625:
191:. This may be done by national standards laboratories operated by the government or by private firms offering metrology services.
1200:
1005:. Fluid Control Research Institute (FCRI), Ministry of Heavy Industries & Public Enterprises, Govt. of India. Archived from
30:
This article is about assessing the accuracy of a measurement device, like a scale or a ruler. For the statistical concept, see
1031:
Quality
Control Training Manual: Comprehensive Training Guide for API, Finished Pharmaceutical and Biotechnologies Laboratories
1266:
1466:
1381:
1354:
1327:
1168:
1039:
962:
154:
1065:
94:
Strictly speaking, the term "calibration" means just the act of comparison and does not include any subsequent adjustment.
397:"...shall be calibrated or verified at periodic intervals established and maintained to assure acceptable reliability..."
506:. An automatic system may also include data collection facilities to automate the gathering of data for record keeping.
860:
1519:
1491:
325:
whenever observations appear questionable or instrument indications do not match the output of surrogate instruments
138:
1343:
Franceschini, Fiorenzo; Galetto, Maurizio; Maisano, Domenico; Mastrogiacomo, Luca; Pralio, Barbara (6 June 2011).
1535:
765:. In the absence of differential pressure both levels would be equal, and this would be used as the zero point.
97:
The calibration standard is normally traceable to a national or international standard held by a metrology body.
951:
ISO 17025: "General requirements for the competence of testing and calibration laboratories" (2005), section 5.
1116:
522:
188:
126:
224:-141 in India. Together, these standards cover instruments that measure various physical quantities such as
553:
503:
341:
209:
standards require that these traceable actions are to a high level and set out how they can be quantified.
112:
This definition states that the calibration process is purely a comparison, but introduces the concept of
340:
could be calibrated so the error of indication or the correction is determined, and adjusted (e.g. via
637:
225:
194:
916:
328:
as specified by a requirement, e.g., customer specification, instrument manufacturer recommendation.
834:
668:
31:
24:
1404:
201:
system which includes formal, periodic, and documented calibration of all measuring instruments.
865:
113:
1225:
895:
599:
317:, or physical damage, which might potentially have compromised the integrity of its calibration
1456:
1371:
1344:
1151:
Ligowski, M.; Jabłoński, Ryszard; Tabe, M. (2011), Jabłoński, Ryszard; Březina, Tomaš (eds.),
708:"Throughout the realm there shall be the same yard of the same size and it should be of iron."
1317:
1029:
769:
495:
364:
717:
1545:
762:
180:
62:
807:
Indirect reading design showing a
Bourdon tube from the front (left) and the rear (right).
514:
All of the information above is collected in a calibration procedure, which is a specific
8:
1398:
829:
541:
491:
277:
35:
1430:
1093:. The National Conference of Standards Laboratories (NCSL) International. Archived from
521:
This exact process is repeated for each of the standards used until transfer standards,
403:
1550:
1540:
873:– tuning, in music, means calibrating musical instruments into playing the right pitch.
614:
249:
1191:
1515:
1487:
1462:
1377:
1350:
1323:
1319:
The
Science of Empire: Scientific Knowledge, Civilization, and Colonial Rule in India
1174:
1164:
1035:
849:
839:
824:
745:
557:
237:
58:
778:
756:
In the direct reading hydrostatic manometer design on the right, applied pressure P
1291:
1156:
977:
843:
610:
548:
about 10% of the original purchase price on a yearly basis, as a commonly accepted
444:
1056:
923:
641:
499:
269:
241:
20:
1003:"Metrology, Pressure, Thermal & Eletrotechnical Measurement and Calibration"
482:
Automatic calibration - A U.S. serviceman using a 3666C auto pressure calibrator
881:
870:
678:
649:
628:
and calibration seem to have been created between the ancient civilizations of
564:
265:
253:
245:
1160:
536:
for other factors that are considered during calibration process development.
1529:
1373:
Foundation: The
History of England from Its Earliest Beginnings to the Tudors
721:
629:
549:
381:
150:
1155:, Mechatronics: Recent Technological and Scientific Advances, p. 227,
1122:. Washington, DC: U.S. Department of Defense. 1 August 1998. Archived from
889:
774:
572:
526:
261:
176:
130:
1233:. U.S. Department of the Interior, Bureau of Reclamation. pp. 70–73.
939:
ISO 9001: "Quality management systems — Requirements" (2008), section 7.6.
332:
In general use, calibration is often regarded as including the process of
19:"Zeroing" redirects here. For the U.S. government antidumping duties, see
885:
773:
stimulated the development of indirect reading instruments, of which the
713:
633:
515:
337:
273:
257:
54:
42:
1342:
963:"Calibration Laboratories: Technical Guide for Mechanical Measurements"
183:
which is directly or indirectly related to national standards (such as
1123:
116:
in relating the accuracies of the device under test and the standard.
749:
673:
618:
533:
314:
206:
198:
46:
655:
621:, thought to be derived from a measurement of the calibre of a gun.
798:
487:
463:
Calibration methods for modern devices can be manual or automatic.
229:
202:
1178:
80:
The outcome of the comparison can result in one of the following:
1455:
Fridman, A. E.; Sabak, Andrew; Makinen, Paul (23 November 2011).
854:
345:
158:
66:
1193:
Military
Handbook: Evaluation of Contractor's Calibration System
727:
1486:. London: The Institute of Measurement and Control. p. 5.
789:
129:
plus a number of derived units) which will be used to provide
90:
an adjustment made to correct the error to an acceptable level
561:
233:
74:
70:
578:
1349:. Springer Science & Business Media. pp. 117–118.
1346:
Distributed Large-Scale Dimensional Metrology: New Insights
973:
645:
447:
and other difficult to diagnose post calibration problems.
184:
146:
1028:
Haider, Syed Imtiaz; Asif, Syed Erfan (16 February 2011).
961:
Faison, C. Douglas; Brickenkamp, Carroll S. (March 2004).
1461:. Springer Science & Business Media. pp. 10–11.
1199:. U.S. Department of Defense. 17 August 1984. p. 7.
740:
One of the earliest pressure measurement devices was the
84:
no significant error being noted on the device under test
732:
509:
1336:
1153:
Procedure for Calibrating Kelvin Probe Force Microscope
1146:
1144:
927:— Basic and general concepts and associated terms (VIM)
288:
Calibration may be required for the following reasons:
142:
1260:"KNC Model 3666 Automatic Pressure Calibration System"
1117:"Calibration Systems Requirements (Military Standard)"
87:
a significant error being noted but no adjustment made
1458:
The Quality of Measurements: A Metrological Reference
1227:
Procedure for calibrating pressure gauges (USBR 1040)
1150:
712:
Other standardization attempts followed, such as the
1397:
Bland, Alfred Edward; Tawney, Richard Henry (1919).
1141:
609:
The words "calibrate" and "calibration" entered the
458:
344:
constants) so that it shows the true temperature in
304:
when a specified usage (operating hours) has elapsed
1454:
1411:
917:
JCGM 200:2008 International vocabulary of metrology
425:
960:
313:after an instrument has been exposed to a shock,
295:after an instrument has been repaired or modified
283:
1527:
1510:Crouch, Stanley & Skoog, Douglas A. (2007).
1448:
1484:Guide to the Measurement of Pressure and Vacuum
1390:
582:An instrument rack with tamper-indicating seals
119:
1475:
909:
744:(1643), which read atmospheric pressure using
1021:
728:The early calibration of pressure instruments
567:devices can be even more costly to maintain.
272:), and, thermodynamic or thermal properties (
1265:. King Nutronics Corporation. Archived from
352:
298:moving from one location to another location
179:is accomplished by a formal comparison to a
107:International Bureau of Weights and Measures
105:The formal definition of calibration by the
16:Check on the accuracy of measurement devices
1396:
1363:
736:Direct reading design of a U-tube manometer
1400:English Economic History: Select Documents
1027:
947:
945:
877:Precision measurement equipment laboratory
307:before and/or after a critical measurement
133:to customer's instruments by calibration.
1309:
935:
933:
742:Mercury barometer, credited to Torricelli
720:from France and the establishment of the
593:
187:in the USA), international standards, or
169:
1376:. St. Martin's Press. pp. 133–134.
1058:Simplified Calibration Interval Analysis
731:
672:
577:
477:
465:
301:when a specified time period has elapsed
73:tone, or a physical artifact, such as a
1417:
1369:
942:
1528:
930:
716:(1225) for liquid measures, until the
656:Calibration of weights and distances (
1481:
1315:
644:and the measurement of gravitational
626:earliest known systems of measurement
510:Process description and documentation
1054:
357:
1512:Principles of Instrumental Analysis
494:used to detect desired levels in a
13:
1420:"Pressure and vacuum measurements"
1370:Ackroyd, Peter (16 October 2012).
861:Measurement Microphone Calibration
100:
14:
1562:
459:Manual and automatic calibrations
797:
788:
34:. For the geometry concept, see
1284:
1252:
1240:from the original on 2013-05-12
1218:
1206:from the original on 2014-12-04
1184:
1091:"ANSI/NCSL Z540.3-2006 (R2013)"
1071:from the original on 2007-04-18
695:Early measurement devices were
426:Standards required and accuracy
1514:. Pacific Grove: Brooks Cole.
1403:. Macmillan Company. pp.
1322:. SUNY Press. pp. 23–24.
1109:
1083:
1048:
995:
954:
284:Instrument calibration prompts
1:
1427:Physical Methods of Chemistry
1292:"the definition of calibrate"
902:
884:– a device used to calibrate
657:
554:scanning electron microscopes
523:certified reference materials
189:certified reference materials
857:Association of European NMIs
370:
310:after an event, for example
164:National Physical Laboratory
120:Modern calibration processes
7:
1418:Tilford, Charles R (1992).
817:
748:. Soon after, water-filled
349:and recording the results.
10:
1567:
1504:
666:
604:
597:
498:, and accessories such as
260:), mechanical quantities (
195:Quality management systems
29:
18:
1429:: 106–173. Archived from
1161:10.1007/978-3-642-23244-2
1034:. CRC Press. p. 49.
552:. Exotic devices such as
353:Basic calibration process
320:sudden changes in weather
226:electromagnetic radiation
1482:CuscĂł, Laurence (1998).
835:Calibration (statistics)
669:Weights and Measures Act
32:Calibration (statistics)
25:Zeroing (disambiguation)
866:Measurement uncertainty
781:is a notable example.
244:), time and frequency (
220:150-2G in the U.S. and
114:measurement uncertainty
1536:Accuracy and precision
1316:Baber, Zaheer (1996).
896:Systems of measurement
842:– used to calibrate a
737:
692:
600:History of measurement
594:Historical development
583:
483:
471:
278:temperature controller
197:call for an effective
170:Quality of calibration
57:values delivered by a
23:. For other uses, see
770:Industrial Revolution
735:
676:
617:, in descriptions of
581:
496:hydraulic accumulator
481:
469:
365:engineering tolerance
53:is the comparison of
1055:Bare, Allen (2006).
970:NIST Handbook 150-2G
763:atmospheric pressure
529:of the calibration.
63:calibration standard
830:Calibrated geometry
613:as recently as the
542:routine maintenance
492:pressure transducer
36:Calibrated geometry
922:2019-10-31 at the
738:
718:Mètre des Archives
704:Assize of Measures
693:
615:American Civil War
584:
484:
472:
250:ionizing radiation
1468:978-1-4614-1478-0
1383:978-1-250-01367-5
1356:978-0-85729-543-9
1329:978-0-7914-2919-8
1170:978-3-642-23244-2
1041:978-1-4398-4994-1
850:Deadweight tester
840:Color calibration
825:Calibration curve
558:gas chromatograph
358:Purpose and scope
238:sound level meter
59:device under test
1558:
1498:
1497:
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1016:
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993:
992:
990:
988:
982:
976:. Archived from
967:
958:
952:
949:
940:
937:
928:
913:
844:computer monitor
801:
792:
690:
689:
685:
677:An example of a
662:
659:
611:English language
445:tolerance stacks
292:a new instrument
61:with those of a
1566:
1565:
1561:
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1559:
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1556:
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1190:
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1012:
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1009:on 14 June 2015
1001:
1000:
996:
986:
984:
980:
965:
959:
955:
950:
943:
938:
931:
924:Wayback Machine
914:
910:
905:
900:
886:weighing scales
820:
811:
810:
809:
808:
804:
803:
802:
794:
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642:dividing engine
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512:
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373:
360:
355:
286:
270:pressure switch
242:noise dosimeter
172:
122:
103:
101:BIPM Definition
45:technology and
39:
28:
21:Zeroing (trade)
17:
12:
11:
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654:
650:weighing scale
606:
603:
598:Main article:
595:
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565:interferometer
511:
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415:MIL-STD-45662A
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266:pressure gauge
254:Geiger counter
246:intervalometer
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550:rule-of-thumb
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1440:28 November
1276:28 November
1244:28 November
1210:28 November
1133:28 November
1101:28 November
1075:28 November
888:that weigh
846:or display.
714:Magna Carta
634:Mesopotamia
516:test method
342:calibration
338:thermometer
274:thermometer
258:light meter
166:in the UK.
55:measurement
51:calibration
43:measurement
1530:Categories
1179:2011935381
903:References
750:manometers
667:See also:
502:and gauge
256:), light (
125:(the main
1551:Metrology
1541:Standards
619:artillery
534:Metrology
382:ISO 17025
371:Frequency
334:adjusting
315:vibration
230:RF probes
207:ISO 17025
199:metrology
47:metrology
1301:18 March
1235:Archived
1201:Archived
1066:Archived
920:Archived
818:See also
648:using a
636:and the
504:fittings
488:Nitrogen
404:ISO-9001
203:ISO 9000
181:standard
127:SI units
1505:Sources
1013:14 June
987:14 June
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686:⁄
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346:Celsius
159:Germany
149:in the
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630:Egypt
562:laser
234:sound
75:meter
71:sound
1516:ISBN
1488:ISBN
1463:ISBN
1442:2014
1378:ISBN
1351:ISBN
1324:ISBN
1303:2018
1278:2014
1246:2014
1212:2014
1175:LCCN
1165:ISBN
1135:2014
1103:2014
1077:2014
1036:ISBN
1015:2015
989:2015
974:NIST
768:The
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532:See
490:, a
222:NABL
218:NIST
205:and
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