SherbyNet - /page/wikibook/entry.mu

Micron Document

<!DOCTYPE html>

<title>Calibration</title>

</head>

<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Calibration</span></span>

</h1>

</header>

/* start https://en.wikipedia.org/ */

.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}

/* end https://en.wikipedia.org/ */

</style><div role="note" class="hatnote navigation-not-searchable">"Zeroing" redirects here. For the U.S. government antidumping duties, see <a href="Zeroing_(trade)" title="Zeroing (trade)">Zeroing (trade)</a>. For other uses, see <a href="Zeroing_(disambiguation)" class="mw-disambig" title="Zeroing (disambiguation)">Zeroing (disambiguation)</a>.</div>

<div role="note" class="hatnote navigation-not-searchable">This article is about assessing the accuracy of a measurement device, like a scale or a ruler. For the statistical concept, see <a href="Calibration_(statistics)" title="Calibration (statistics)">Calibration (statistics)</a>. For the geometry concept, see <a href="Calibrated_geometry" title="Calibrated geometry">Calibrated geometry</a>.</div>

<p>In <a href="Measurement" title="Measurement">measurement</a> technology and <a href="Metrology" title="Metrology">metrology</a>, <b>calibration</b> is the comparison of <a href="Measurement" title="Measurement">measurement</a> values delivered by a <a href="Device_under_test" title="Device under test">device under test</a> with those of a <a href="Standard_(metrology)" title="Standard (metrology)">calibration standard</a> 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 <a href="Voltage" title="Voltage">voltage</a>, a <a href="Sound" title="Sound">sound</a> tone, or a physical artifact, such as a <a href="Meter" class="mw-redirect" title="Meter">meter</a> ruler.

</p><p>The outcome of the comparison can result in one of the following:

</p>

<ul><li>no significant error being noted on the device under test</li>

<li>a significant error being noted but no adjustment made</li>

<li>an adjustment made to correct the error to an acceptable level</li></ul>

<p>Strictly speaking, the term "calibration" means just the act of comparison and does not include any subsequent adjustment.

</p><p>The calibration standard is normally traceable to a national or international standard held by a metrology body.

</p>

<div class="mw-heading mw-heading2"><h2 id="BIPM_Definition">BIPM Definition</h2></div>

<p>The formal definition of calibration by the <a href="International_Bureau_of_Weights_and_Measures" title="International Bureau of Weights and Measures">International Bureau of Weights and Measures</a> (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."<sup id="cite_ref-metrology_terms_1-0" class="reference"><a href="#cite_note-metrology_terms-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>

</p><p>This definition states that the calibration process is purely a comparison, but introduces the concept of <a href="Measurement_uncertainty" title="Measurement uncertainty">measurement uncertainty</a> in relating the accuracies of the device under test and the standard.

</p>

<div class="mw-heading mw-heading2"><h2 id="Modern_calibration_processes">Modern calibration processes</h2></div>

<p>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 (the main <a href="International_System_of_Units" title="International System of Units">SI units</a> plus a number of derived units) which will be used to provide <a href="Traceability" title="Traceability">traceability</a> to customer's instruments by calibration.

</p><p>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 <a href="National_Physical_Laboratory%2C_UK" class="mw-redirect" title="National Physical Laboratory, UK">NPL</a> in the <a href="UK" class="mw-redirect" title="UK">UK</a>, <a href="NIST" class="mw-redirect" title="NIST">NIST</a> in the <a href="United_States" title="United States">United States</a>, <a href="Physikalisch-Technische_Bundesanstalt" title="Physikalisch-Technische Bundesanstalt">PTB</a> in <a href="Germany" title="Germany">Germany</a> 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 <a href="National_Physical_Laboratory_(United_Kingdom)" title="National Physical Laboratory (United Kingdom)">National Physical Laboratory</a> in the UK.

</p>

<div class="mw-heading mw-heading3"><h3 id="Quality_of_calibration">Quality of calibration</h3></div>

<p>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 <a href="Traceability" title="Traceability">traceability</a> is accomplished by a formal comparison to a <a href="Standard_(metrology)" title="Standard (metrology)">standard</a> which is directly or indirectly related to national standards (such as <a href="NIST" class="mw-redirect" title="NIST">NIST</a> in the USA), international standards, or <a href="Certified_reference_materials" title="Certified reference materials">certified reference materials</a>. This may be done by national standards laboratories operated by the government or by private firms offering metrology services.

</p><p><a href="Quality_management_system" title="Quality management system">Quality management systems</a> call for an effective <a href="Metrology" title="Metrology">metrology</a> system which includes formal, periodic, and documented calibration of all measuring instruments. <a href="ISO_9000" class="mw-redirect" title="ISO 9000">ISO 9000</a><sup id="cite_ref-iso9001_2-0" class="reference"><a href="#cite_note-iso9001-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> and <a href="ISO_17025" class="mw-redirect" title="ISO 17025">ISO 17025</a><sup id="cite_ref-iso17025_3-0" class="reference"><a href="#cite_note-iso17025-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> standards require that these traceable actions are to a high level and set out how they can be quantified.

</p><p>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 state. Whenever this does happen, it must be in writing and authorized by a manager with the technical assistance of a calibration technician.

</p><p>Measuring devices and instruments are categorized according to the physical quantities they are designed to measure. These vary internationally, e.g., <a href="National_Institute_of_Standards_and_Technology" title="National Institute of Standards and Technology">NIST</a> 150-2G in the U.S.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> and <a href="National_Accreditation_Board_for_Testing_and_Calibration_Laboratories" title="National Accreditation Board for Testing and Calibration Laboratories">NABL</a>-141 in India.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> Together, these standards cover instruments that measure various physical quantities such as <a href="Electromagnetic_radiation" title="Electromagnetic radiation">electromagnetic radiation</a> (<a href="RF_probe" title="RF probe">RF probes</a>), <a href="Sound" title="Sound">sound</a> (<a href="Sound_level_meter" title="Sound level meter">sound level meter</a> or <a href="Noise_dosimeter" title="Noise dosimeter">noise dosimeter</a>), time and frequency (<a href="Intervalometer" title="Intervalometer">intervalometer</a>), <a href="Ionizing_radiation" title="Ionizing radiation">ionizing radiation</a> (<a href="Geiger_counter" title="Geiger counter">Geiger counter</a>), light (<a href="Light_meter" title="Light meter">light meter</a>), mechanical quantities (<a href="Limit_switch" title="Limit switch">limit switch</a>, <a href="Pressure_gauge" class="mw-redirect" title="Pressure gauge">pressure gauge</a>, <a href="Pressure_switch" title="Pressure switch">pressure switch</a>), and, thermodynamic or thermal properties (<a href="Thermometer" title="Thermometer">thermometer</a>, <a href="Temperature_control" title="Temperature control">temperature controller</a>). 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.

</p>

<div class="mw-heading mw-heading2"><h2 id="Instrument_calibration_prompts">Instrument calibration prompts</h2></div>

<p>Calibration may be required for the following reasons:

</p>

<ul><li>a new instrument</li>

<li>after an instrument has been repaired or modified</li>

<li>moving from one location to another location</li>

<li>when a specified time period has elapsed</li>

<li>when a specified usage (operating hours) has elapsed</li>

<li>before and/or after a critical measurement</li>

<li>after an event, for example

<ul><li>after an instrument has been exposed to a shock, <a href="Vibration" title="Vibration">vibration</a>, or physical damage, which might potentially have compromised the integrity of its calibration</li>

<li>sudden changes in weather</li></ul></li>

<li>whenever observations appear questionable or instrument indications do not match the output of surrogate instruments</li>

<li>as specified by a requirement, e.g., customer specification, instrument manufacturer recommendation.</li></ul>

<p>In general use, calibration is often regarded as including the process of <b>adjusting</b> the output or indication on a measurement instrument to agree with value of the applied standard, within a specified accuracy. For example, a <a href="Thermometer" title="Thermometer">thermometer</a> could be calibrated so the error of indication or the correction is determined, and adjusted (e.g. via <a href="Operational_definition#Temperature" title="Operational definition">calibration</a> constants) so that it shows the true temperature in <a href="Celsius" title="Celsius">Celsius</a> 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 and recording the results.

</p>

<div class="mw-heading mw-heading2"><h2 id="Basic_calibration_process">Basic calibration process</h2></div>

<div class="mw-heading mw-heading3"><h3 id="Purpose_and_scope">Purpose and scope</h3></div>

<p>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 <a href="Engineering_tolerance" title="Engineering tolerance">engineering tolerance</a>" when used within the stated environmental conditions over some reasonable period of time.<sup id="cite_ref-HaiderAsif2011_6-0" class="reference"><a href="#cite_note-HaiderAsif2011-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> 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.

</p>

<div class="mw-heading mw-heading3"><h3 id="Intervals">Intervals</h3></div>

<p>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 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:<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup>

</p>

<dl><dd>"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.”</dd></dl></dd>

<dl><dd>"...shall be calibrated or verified at periodic intervals established and maintained to assure acceptable reliability..."</dd></dl></dd>

<dl><dd>"Where necessary to ensure valid results, measuring equipment shall...be calibrated or verified at specified intervals, or prior to use...”</dd></dl></dd>

<dl><dd>"... 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."</dd></dl></dd></dl>

<div class="mw-heading mw-heading3"><h3 id="Standards_required_and_accuracy">Standards required and accuracy</h3></div>

<p>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 uncertainty of all of the standards involved is considered to be insignificant when the final measurement is also made with the 4:1 ratio.<sup id="cite_ref-JablonskiBrezina2011_10-0" class="reference"><a href="#cite_note-JablonskiBrezina2011-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> 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.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup>

</p><p>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.<sup id="cite_ref-JablonskiBrezina2011_10-1" class="reference"><a href="#cite_note-JablonskiBrezina2011-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> 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 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.

</p><p>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 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.

</p><p>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 <a href="Tolerance_stacks" class="mw-redirect" title="Tolerance stacks">tolerance stacks</a> and other difficult to diagnose post calibration problems.

</p><p>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 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.

</p><p>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.

</p>

<div class="mw-heading mw-heading3"><h3 id="Manual_and_automatic_calibrations">Manual and automatic calibrations</h3></div>

<p>Calibration methods for modern devices can be manual or automatic.

</p>

<p>As an example, a manual process may be used for calibration of a pressure gauge. The procedure requires multiple steps,<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> 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 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.

</p>

<p>An automatic pressure calibrator <sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> is a device that combines an electronic control unit, a pressure intensifier used to compress a gas such as <a href="Nitrogen" title="Nitrogen">Nitrogen</a>, a <a href="Pressure_transducer" class="mw-redirect" title="Pressure transducer">pressure transducer</a> used to detect desired levels in a <a href="Hydraulic_accumulator" title="Hydraulic accumulator">hydraulic accumulator</a>, and accessories such as <a href="Trap_(plumbing)" title="Trap (plumbing)">liquid traps</a> and gauge <a href="Piping_and_plumbing_fittings" class="mw-redirect" title="Piping and plumbing fittings">fittings</a>. An automatic system may also include data collection facilities to automate the gathering of data for record keeping.

</p>

<div class="mw-heading mw-heading3"><h3 id="Process_description_and_documentation">Process description and documentation</h3></div>

<p>All of the information above is collected in a calibration procedure, which is a specific <a href="Test_method" title="Test method">test method</a>. 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.

</p><p>This exact process is repeated for each of the standards used until transfer standards, <a href="Certified_reference_materials" title="Certified reference materials">certified reference materials</a> and/or natural physical constants, the measurement standards with the least uncertainty in the laboratory, are reached. This establishes the <a href="Traceability" title="Traceability">traceability</a> of the calibration.

</p><p>See <a href="Metrology" title="Metrology">Metrology</a> for other factors that are considered during calibration process development.

</p><p>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 <a href="Planned_maintenance" class="mw-redirect" title="Planned maintenance">routine maintenance</a> is performed. After routine maintenance and deficiencies detected during calibration are addressed, an "as-left" calibration is performed.

</p><p>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 about 10% of the original purchase price on a yearly basis, as a commonly accepted <a href="Rule-of-thumb" class="mw-redirect" title="Rule-of-thumb">rule-of-thumb</a>. Exotic devices such as <a href="Scanning_electron_microscope" title="Scanning electron microscope">scanning electron microscopes</a>, <a href="Gas_chromatograph" class="mw-redirect" title="Gas chromatograph">gas chromatograph</a> systems and <a href="Laser" title="Laser">laser</a> <a href="Interferometer" class="mw-redirect" title="Interferometer">interferometer</a> devices can be even more costly to maintain.

</p><p>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 <a href="Oscilloscope" title="Oscilloscope">oscilloscope</a>. 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.

</p>

<p>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 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.

</p><p>When the instruments being calibrated are integrated with computers, the integrated computer programs and any calibration corrections are also under control.

</p>

<div class="mw-heading mw-heading2"><h2 id="Historical_development">Historical development</h2></div>

<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="History_of_measurement" title="History of measurement">History of measurement</a></div>

<div class="mw-heading mw-heading3"><h3 id="Origins">Origins</h3></div>

<p>The words "calibrate" and "calibration" entered the <a href="English_language" title="English language">English language</a> as recently as the <a href="American_Civil_War" title="American Civil War">American Civil War</a>,<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> in descriptions of <a href="Artillery" title="Artillery">artillery</a>, thought to be derived from a measurement of the calibre of a gun.

</p><p>Some of the <a href="History_of_measurement#Earliest_known_measurement_systems" title="History of measurement">earliest known systems of measurement</a> and calibration seem to have been created between the ancient civilizations of <a href="Ancient_Egypt" title="Ancient Egypt">Egypt</a>, <a href="Mesopotamia" title="Mesopotamia">Mesopotamia</a> and the <a href="Indus_Valley_civilization" class="mw-redirect" title="Indus Valley civilization">Indus Valley</a>, with excavations revealing the use of angular gradations for construction.<sup id="cite_ref-Baber1996_15-0" class="reference"><a href="#cite_note-Baber1996-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> The term "calibration" was likely first associated with the precise division of linear distance and angles using a <a href="Dividing_engine" title="Dividing engine">dividing engine</a> and the measurement of gravitational <a href="Mass" title="Mass">mass</a> using a <a href="Weighing_scale" title="Weighing scale">weighing scale</a>. 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.<sup id="cite_ref-FranceschiniGaletto2011_16-0" class="reference"><a href="#cite_note-FranceschiniGaletto2011-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup>

</p>

<div class="mw-heading mw-heading3"><h3 id="Calibration_of_weights_and_distances_(c._1100_CE)">Calibration of weights and distances (<span title="circa">c.</span><span style="white-space:nowrap;"> 1100 CE</span>)</h3></div>

<div role="note" class="hatnote navigation-not-searchable">See also: <a href="Weights_and_Measures_Act" title="Weights and Measures Act">Weights and Measures Act</a></div>

<p>Early measurement devices were <i>direct</i>, 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."<sup id="cite_ref-Ackroyd2012_17-0" class="reference"><a href="#cite_note-Ackroyd2012-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> However, it wasn't until the reign of Richard I (1197) that we find documented evidence.<sup id="cite_ref-BlandTawney1919_18-0" class="reference"><a href="#cite_note-BlandTawney1919-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup>

</p>

<dl><dd><i>Assize of Measures</i></dd>

<dd>"Throughout the realm there shall be the same yard of the same size and it should be of iron."</dd></dl>

<p>Other standardization attempts followed, such as the <a href="Magna_Carta" title="Magna Carta">Magna Carta</a> (1225) for liquid measures, until the <a href="M%C3%A8tre_des_Archives" class="mw-redirect" title="Mètre des Archives">Mètre des Archives</a> from France and the establishment of the <a href="Metric_system" title="Metric system">Metric system</a>.

</p>

<div class="mw-heading mw-heading3"><h3 id="The_early_calibration_of_pressure_instruments">The early calibration of pressure instruments</h3></div>

<p>One of the earliest pressure measurement devices was the <a href="Evangelista_Torricelli#Suction_pumps_and_the_invention_of_the_barometer" title="Evangelista Torricelli">Mercury barometer, credited to Torricelli</a> (1643),<sup id="cite_ref-tilford1992pressure_19-0" class="reference"><a href="#cite_note-tilford1992pressure-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> which read atmospheric pressure using <a href="Mercury_(element)" title="Mercury (element)">Mercury</a>. Soon after, water-filled <a href="Manometer" class="mw-redirect" title="Manometer">manometers</a> 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.

</p><p>In the direct reading hydrostatic manometer design on the right, applied pressure P<sub>a</sub> 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 <a href="Atmospheric_pressure" title="Atmospheric pressure">atmospheric pressure</a>. In the absence of differential pressure both levels would be equal, and this would be used as the zero point.

</p><p>The <a href="Industrial_Revolution" title="Industrial Revolution">Industrial Revolution</a> saw the adoption of "indirect" pressure measuring devices, which were more practical than the manometer.<sup id="cite_ref-FridmanSabak2011_20-0" class="reference"><a href="#cite_note-FridmanSabak2011-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup>

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.<sup id="cite_ref-cusco1998guide_21-0" class="reference"><a href="#cite_note-cusco1998guide-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> This stimulated the development of indirect reading instruments, of which the <a href="Bourdon_tube" class="mw-redirect" title="Bourdon tube">Bourdon tube</a> invented by <a href="Eug%C3%A8ne_Bourdon" title="Eugène Bourdon">Eugène Bourdon</a> is a notable example.

</p>

/* start https://en.wikipedia.org/ */

.mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}

/* end https://en.wikipedia.org/ */

</style><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:208px;max-width:208px"><div class="trow"><div class="tsingle" style="width:102px;max-width:102px"><div class="thumbimage"><span typeof="mw:File"></span></div></div><div class="tsingle" style="width:102px;max-width:102px"><div class="thumbimage"><span typeof="mw:File"></span></div></div></div><div class="trow" style="display:flex"><div class="thumbcaption">Indirect reading design showing a Bourdon tube from the front (left) and the rear (right).</div></div></div></div>

<p>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 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.

</p>

/* start https://en.wikipedia.org/ */

.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .infobox .side-box{font-size:100%}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:720px){.mw-parser-output .side-box{width:238px}.mw-parser-output .side-box-right{clear:right;float:right;margin-left:1em}.mw-parser-output .side-box-left{margin-right:1em}}

/* end https://en.wikipedia.org/ */

</style><style data-mw-deduplicate="TemplateStyles:r1237033735">

/* start https://en.wikipedia.org/ */

@media print{body.ns-0 .mw-parser-output .sistersitebox{display:none!important}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}

/* end https://en.wikipedia.org/ */

</style><div class="side-box side-box-right sistersitebox"><style data-mw-deduplicate="TemplateStyles:r1126788409">

/* start https://en.wikipedia.org/ */

.mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}

/* end https://en.wikipedia.org/ */

</style>

<div class="side-box-text plainlist">Look up <i><b><a href="https://en.wiktionary.org/wiki/calibration" class="extiw external" title="wiktionary:calibration">calibration</a></b></i> in Wiktionary, the free dictionary.</div></div>

</div>

/* start https://en.wikipedia.org/ */

.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}

/* end https://en.wikipedia.org/ */

</style><div class="div-col" style="column-width: 22em;">

<ul><li><a href="Calibration_curve" title="Calibration curve">Calibration curve</a></li>

<li><a href="Calibrated_geometry" title="Calibrated geometry">Calibrated geometry</a></li>

<li><a href="Calibration_(statistics)" title="Calibration (statistics)">Calibration (statistics)</a></li>

<li><a href="Color_calibration" title="Color calibration">Color calibration</a> – used to calibrate a <a href="Computer_monitor" title="Computer monitor">computer monitor</a> or display.</li>

<li><a href="Deadweight_tester" title="Deadweight tester">Deadweight tester</a></li>

<li><a href="EURAMET" title="EURAMET">EURAMET</a> Association of European NMIs</li>

<li><a href="Measurement_Microphone_Calibration" class="mw-redirect" title="Measurement Microphone Calibration">Measurement Microphone Calibration</a></li>

<li><a href="Measurement_uncertainty" title="Measurement uncertainty">Measurement uncertainty</a></li>

<li><a href="Musical_tuning" title="Musical tuning">Musical tuning</a> – tuning, in music, means calibrating musical instruments into playing the right pitch.</li>

<li><a href="Precision_measurement_equipment_laboratory" title="Precision measurement equipment laboratory">Precision measurement equipment laboratory</a></li>

<li><a href="Scale_test_car" title="Scale test car">Scale test car</a> – a device used to calibrate <a href="Truck_scale" title="Truck scale">weighing scales</a> that weigh <a href="Railroad_car" title="Railroad car">railroad cars</a>.</li>

<li><a href="Systems_of_measurement" class="mw-redirect" title="Systems of measurement">Systems of measurement</a></li></ul>

</div>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

/* start https://en.wikipedia.org/ */

.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}

/* end https://en.wikipedia.org/ */

</style><div class="reflist">

<li id="cite_note-metrology_terms-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-metrology_terms_1-0">^</a></b></span> <span class="reference-text"><i><a rel="nofollow" class="external text" href="http://www.bipm.org/utils/common/documents/jcgm/JCGM_200_2008.pdf">JCGM 200:2008 International vocabulary of metrology</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20191031152041/https://www.bipm.org/utils/common/documents/jcgm/JCGM_200_2008.pdf">Archived</a> 2019-10-31 at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a></i> — Basic and general concepts and associated terms (VIM)</span>

</li>

<li id="cite_note-iso9001-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-iso9001_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-iso9001_2-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">ISO 9001: "Quality management systems — Requirements" (2008), section 7.6.</span>

</li>

<li id="cite_note-iso17025-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-iso17025_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-iso17025_3-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">ISO 17025: "General requirements for the competence of testing and calibration laboratories" (2005), section 5.</span>

</li>

/* start https://en.wikipedia.org/ */

.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("./mw/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("./mw/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("./mw/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("./mw/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}

/* end https://en.wikipedia.org/ */

</style><cite id="CITEREFFaisonBrickenkamp2004" class="citation journal cs1">Faison, C. Douglas; Brickenkamp, Carroll S. (March 2004). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150512215554/http://www.nist.gov/nvlap/upload/hb150-2g-1.pdf">"Calibration Laboratories: Technical Guide for Mechanical Measurements"</a> <span class="cs1-format">(PDF)</span>. <i>NIST Handbook 150-2G</i>. <a href="NIST" class="mw-redirect" title="NIST">NIST</a>. Archived from <a rel="nofollow" class="external text" href="https://www.nist.gov/nvlap/upload/hb150-2g-1.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 12 May 2015<span class="reference-accessdate">. Retrieved <span class="nowrap">14 June</span> 2015</span>.</cite></span>

</li>

<li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150614205726/http://www.fcriindia.com/national-training-2/metrology-pressure-thermal-electrotechnical-measurement-calibration/">"Metrology, Pressure, Thermal & Eletrotechnical Measurement and Calibration"</a>. Fluid Control Research Institute (FCRI), Ministry of Heavy Industries & Public Enterprises, Govt. of India. Archived from <a rel="nofollow" class="external text" href="http://www.fcriindia.com/national-training-2/metrology-pressure-thermal-electrotechnical-measurement-calibration/">the original</a> on 14 June 2015<span class="reference-accessdate">. Retrieved <span class="nowrap">14 June</span> 2015</span>.</cite></span>

</li>

<li id="cite_note-HaiderAsif2011-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-HaiderAsif2011_6-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFHaiderAsif2011" class="citation book cs1">Haider, Syed Imtiaz; Asif, Syed Erfan (16 February 2011). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=-djll_c9Z9MC&pg=PA49"><i>Quality Control Training Manual: Comprehensive Training Guide for API, Finished Pharmaceutical and Biotechnologies Laboratories</i></a>. CRC Press. p. 49. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-1-4398-4994-1</bdi>.</cite></span>

</li>

<li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><cite id="CITEREFBare2006" class="citation book cs1">Bare, Allen (2006). <a rel="nofollow" class="external text" href="http://sti.srs.gov/fulltext/2006/ms2006099.pdf"><i>Simplified Calibration Interval Analysis</i></a> <span class="cs1-format">(PDF)</span>. Aiken, SC: NCSL International Workshop and Symposium, under contract with the Office of Scientific and Technical Information, U.S. Department of Energy. pp. <span class="nowrap">1–</span>2. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20070418143512/http://sti.srs.gov/fulltext/2006/ms2006099.pdf">Archived</a> <span class="cs1-format">(PDF)</span> from the original on 2007-04-18<span class="reference-accessdate">. Retrieved <span class="nowrap">28 November</span> 2014</span>.</cite></span>

</li>

<li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20141120230954/http://www.ncsli.org/I/i/p/z3/c/a/p/NCSL_International_Z540.3_Standard.aspx?hkey=7de83171-16ff-416c-9182-94c8447fb300">"ANSI/NCSL Z540.3-2006 (R2013)"</a>. The National Conference of Standards Laboratories (NCSL) International. Archived from <a rel="nofollow" class="external text" href="http://www.ncsli.org/I/i/p/z3/c/a/p/NCSL_International_Z540.3_Standard.aspx?hkey=7de83171-16ff-416c-9182-94c8447fb300">the original</a> on 2014-11-20<span class="reference-accessdate">. Retrieved <span class="nowrap">28 November</span> 2014</span>.</cite></span>

</li>

<li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20051030004254/http://medivactech.com/revA.pdf">"Calibration Systems Requirements (Military Standard)"</a> <span class="cs1-format">(PDF)</span>. Washington, DC: U.S. Department of Defense. 1 August 1998. Archived from <a rel="nofollow" class="external text" href="http://www.medivactech.com/revA.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 2005-10-30<span class="reference-accessdate">. Retrieved <span class="nowrap">28 November</span> 2014</span>.</cite></span>

</li>

<li id="cite_note-JablonskiBrezina2011-10"><span class="mw-cite-backlink">^ <a href="#cite_ref-JablonskiBrezina2011_10-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-JablonskiBrezina2011_10-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><cite id="CITEREFLigowskiJabłońskiTabe2011" class="citation cs2">Ligowski, M.; Jabłoński, Ryszard; Tabe, M. (2011), Jabłoński, Ryszard; Březina, Tomaš (eds.), <i>Procedure for Calibrating Kelvin Probe Force Microscope</i>, Mechatronics: Recent Technological and Scientific Advances, p. 227, <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2F978-3-642-23244-2">10.1007/978-3-642-23244-2</a>, <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-3-642-23244-2</bdi>, <a href="LCCN_(identifier)" class="mw-redirect" title="LCCN (identifier)">LCCN</a> <a rel="nofollow" class="external text" href="https://lccn.loc.gov/2011935381">2011935381</a></cite></span>

</li>

<li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><cite class="citation book cs1"><a rel="nofollow" class="external text" href="http://www.barringer1.com/mil_files/MIL-HDBK-52.pdf"><i>Military Handbook: Evaluation of Contractor's Calibration System</i></a> <span class="cs1-format">(PDF)</span>. U.S. Department of Defense. 17 August 1984. p. 7. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20141204234336/http://www.barringer1.com/mil_files/MIL-HDBK-52.pdf">Archived</a> <span class="cs1-format">(PDF)</span> from the original on 2014-12-04<span class="reference-accessdate">. Retrieved <span class="nowrap">28 November</span> 2014</span>.</cite></span>

</li>

<li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text"><cite class="citation book cs1"><a rel="nofollow" class="external text" href="https://www.usbr.gov/pmts/geotech/rock/EMpart_2/USBR1040.pdf"><i>Procedure for calibrating pressure gauges (USBR 1040)</i></a> <span class="cs1-format">(PDF)</span>. U.S. Department of the Interior, Bureau of Reclamation. pp. <span class="nowrap">70–</span>73. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20130512121612/http://www.usbr.gov/pmts/geotech/rock/EMpart_2/USBR1040.pdf">Archived</a> <span class="cs1-format">(PDF)</span> from the original on 2013-05-12<span class="reference-accessdate">. Retrieved <span class="nowrap">28 November</span> 2014</span>.</cite></span>

</li>

<li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20141204112439/http://www.kingnutronics.com/Model%203666%20Automatic%20Pressure%20Calibration%20System.pdf">"KNC Model 3666 Automatic Pressure Calibration System"</a> <span class="cs1-format">(PDF)</span>. King Nutronics Corporation. Archived from <a rel="nofollow" class="external text" href="http://www.kingnutronics.com/Model%203666%20Automatic%20Pressure%20Calibration%20System.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 2014-12-04<span class="reference-accessdate">. Retrieved <span class="nowrap">28 November</span> 2014</span>.</cite></span>

</li>

<li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://dictionary.reference.com/browse/calibrate">"the definition of calibrate"</a>. <i>Dictionary.com</i><span class="reference-accessdate">. Retrieved <span class="nowrap">18 March</span> 2018</span>.</cite></span>

</li>

<li id="cite_note-Baber1996-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-Baber1996_15-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFBaber1996" class="citation book cs1">Baber, Zaheer (1996). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=ucDBJSxaCPYC&pg=PA14"><i>The Science of Empire: Scientific Knowledge, Civilization, and Colonial Rule in India</i></a>. SUNY Press. pp. <span class="nowrap">23–</span>24. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-7914-2919-8</bdi>.</cite></span>

</li>

<li id="cite_note-FranceschiniGaletto2011-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-FranceschiniGaletto2011_16-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFFranceschiniGalettoMaisanoMastrogiacomo2011" class="citation book cs1">Franceschini, Fiorenzo; Galetto, Maurizio; Maisano, Domenico; Mastrogiacomo, Luca; Pralio, Barbara (6 June 2011). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=bIwbFtXyMcMC&pg=PA117"><i>Distributed Large-Scale Dimensional Metrology: New Insights</i></a>. Springer Science & Business Media. pp. <span class="nowrap">117–</span>118. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-85729-543-9</bdi>.</cite></span>

</li>

<li id="cite_note-Ackroyd2012-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-Ackroyd2012_17-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFAckroyd2012" class="citation book cs1">Ackroyd, Peter (16 October 2012). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=Z2XHs80O0OEC&pg=PT133"><i>Foundation: The History of England from Its Earliest Beginnings to the Tudors</i></a>. St. Martin's Press. pp. <span class="nowrap">133–</span>134. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-1-250-01367-5</bdi>.</cite></span>

</li>

<li id="cite_note-BlandTawney1919-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-BlandTawney1919_18-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFBlandTawney1919" class="citation book cs1">Bland, Alfred Edward; Tawney, Richard Henry (1919). <a rel="nofollow" class="external text" href="https://archive.org/details/ajc0024.0001.001.umich.edu"><i>English Economic History: Select Documents</i></a>. Macmillan Company. pp. <a rel="nofollow" class="external text" href="https://archive.org/details/ajc0024.0001.001.umich.edu/page/154">154</a>–155.</cite></span>

</li>

<li id="cite_note-tilford1992pressure-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-tilford1992pressure_19-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFTilford1992" class="citation journal cs1">Tilford, Charles R (1992). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20141205044516/http://www.glb.nist.gov/calibrations/upload/pmc-2.pdf">"Pressure and vacuum measurements"</a> <span class="cs1-format">(PDF)</span>. <i>Physical Methods of Chemistry</i>: <span class="nowrap">106–</span>173. Archived from <a rel="nofollow" class="external text" href="http://www.glb.nist.gov/calibrations/upload/pmc-2.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 2014-12-05<span class="reference-accessdate">. Retrieved <span class="nowrap">28 November</span> 2014</span>.</cite></span>

</li>

<li id="cite_note-FridmanSabak2011-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-FridmanSabak2011_20-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFFridmanSabakMakinen2011" class="citation book cs1">Fridman, A. E.; Sabak, Andrew; Makinen, Paul (23 November 2011). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=kyX-1VzPokQC&pg=PA111"><i>The Quality of Measurements: A Metrological Reference</i></a>. Springer Science & Business Media. pp. <span class="nowrap">10–</span>11. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-1-4614-1478-0</bdi>.</cite></span>

</li>

<li id="cite_note-cusco1998guide-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-cusco1998guide_21-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFCuscó1998" class="citation book cs1">Cuscó, Laurence (1998). <i>Guide to the Measurement of Pressure and Vacuum</i>. London: The Institute of Measurement and Control. p. 5. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-904457-29-X</bdi>.</cite></span>

</li>

</ol></div></div>

<div class="mw-heading mw-heading2"><h2 id="Sources">Sources</h2></div>

<ul><li>Crouch, Stanley & Skoog, Douglas A. (2007). <i>Principles of Instrumental Analysis</i>. Pacific Grove: Brooks Cole. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-495-01201-7</bdi>.</li></ul></div><div><div class="zim-footer">

This article is issued from <a class="external text" title="Last edited on 2025-02-13" href="https://en.wikipedia.org/wiki/?title=Calibration&oldid=1275474609">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

</div>

</div></div>

</div>

</main>

</div>

</body></html>