Caliper - Wiki

Caliper 1

Caliper

A vernier caliper

Caliper with graduated bow 0-10 mm

A caliper (British spelling also calliper) is a device used to measurethe distance between two opposing sides of an object. A caliper can beas simple as a compass with inward or outward-facing points. The tipsof the caliper are adjusted to fit across the points to be measured, thecaliper is then removed and the distance read by measuring betweenthe tips with a measuring tool, such as a ruler.

It is used in many fields such as metalworking, mechanicalengineering, gunsmithing, handloading, woodworking, woodturningand in medicine.

Nomenclature variants

A plurale tantum sense of the word "calipers" coexists in natural usagewith the regular noun sense of "caliper". That is, sometimes a caliper istreated cognitively like a pair of glasses or a pair of scissors, resultingin a phrase such as "hand me those calipers" or "those calipers aremine" in reference to one unit. However, this usage is mostlycolloquial and the regular noun sense of caliper usually dominates,especially in writing. There is no rigorous grammatical logic to defendthe plurale tantum sense; it is just the way language sometimesnaturally flows colloquially.

Also existing colloquially but not in formal usage is referring to avernier caliper as a "vernier".

HistoryThe earliest caliper has been found in the Greek Giglio wreck near the Italian coast. The ship find dates to the 6thcentury BC. The wooden piece already featured a fixed and a movable jaw.[1] [2] Although rare finds, caliperremained in use by the Greeks and Romans.[2] [3]

By the Han Dynasty (202 BC – 220 AD), the Chinese also used the sliding caliper, which they made of bronze andmanufactured each tool with an inscription of the day, month, and year it was made (according to Chinese era namesand their lunar calendar).[4]

The modern vernier caliper, reading to thousandths of an inch, was invented by American Joseph R. Brown in 1851.His Brown and Sharpe company inaugurated true precision manufacture in the United States. It was the firstpractical tool for exact measurements that could be sold at a price within the reach of ordinary machinists.[5]

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Types

Inside caliper

Two inside calipers

The inside calipers are used to measure the internal size of an object.• The upper caliper in the image (at the right) requires manual

adjustment prior to fitting, fine setting of this caliper type isperformed by tapping the caliper legs lightly on a handy surfaceuntil they will almost pass over the object. A light push against theresistance of the central pivot screw then spreads the legs to thecorrect dimension and provides the required, consistent feel thatensures a repeatable measurement.

• The lower caliper in the image has an adjusting screw that permits itto be carefully adjusted without removal of the tool from theworkpiece.

Outside caliper

Three outside calipers.

Outside calipers are used to measure the external size of an object.The same observations and technique apply to this type of caliper, asfor the above inside caliper. With some understanding of theirlimitations and usage these instruments can provide a high degree ofaccuracy and repeatability. They are especially useful when measuringover very large distances, consider if the calipers are used to measure alarge diameter pipe. A vernier caliper does not have the depth capacityto straddle this large diameter while at the same time reach theoutermost points of the pipe's diameter.

Divider caliper

A pair of dividers

In the metalworking field divider calipers are used in the process ofmarking out suitable workpieces. The points are sharpened so that theyact as scribers, one leg can then be placed in the dimple created by acenter or prick punch and the other leg pivoted so that it scribes a lineon the workpiece's surface, thus forming an arc or circle.

A divider caliper is also used to measure a distance between two pointson a map. The two caliper's ends are brought to the two points whosedistance is being measured. The caliper's opening is then eithermeasured on a separate ruler and then converted to the actual distance, or it is measured directly on a scale drawn onthe map. On a nautical chart the distance is often measured on the latitude scale appearing on the sides of the map:one minute of arc of latitude is approximately one nautical mile or 1852 metres.

Dividers are also used in the medical profession. They are used to measure electrocardiogram (ECG) lines. Thisinstrument is called an ECG caliper or EKG caliper. These calipers have changed through the years, and there areeven pocket calipers, invented 20 years ago by cardiologist Robert A. Mackin.

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Oddleg caliper

Odd leg calipers

Oddleg calipers, Hermaphrodite calipers or Oddleg jennys, or Ol'Jennys, as pictured on the left, are generally used to scribe a line a setdistance from the edge of workpiece. The bent leg is used to run alongthe workpiece edge while the scriber makes its mark at apredetermined distance, this ensures a line parallel to the edge.

In the diagram at left, the uppermost caliper has a slight shoulder in thebent leg allowing it to sit on the edge more securely, the lower caliperlacks this feature but has a renewable scriber that can be adjusted forwear, as well as being replaced when excessively worn.

Vernier caliper

Parts of a vernier caliper:Outside jaws: used to measure external diameter or width of anobjectInside jaws: used to measure internal diameter of an objectDepth probe: used tomeasure depths of an object or a holeMain scale: scale marked every mmMain scale:

scale marked in inches and fractionsVernier gives interpolated measurements to 1/10 mmor betterVernier gives interpolated measurements in fractions of an inchRetainer: used to

block movable part to allow the easy transferring of a measurement

The vernier, dial, and digital calipersgive a direct reading of the distancemeasured to high accuracy. They arefunctionally identical, with differentways of reading the result. Thesecalipers comprise a calibrated scalewith a fixed jaw, and another jaw, witha pointer, that slides along the scale.The distance between the jaws is thenread in different ways for the threetypes.The simplest method is to read theposition of the pointer directly on thescale. When the pointer is between two markings, the user can mentally interpolate to improve the precision of thereading. This would be a simple calibrated caliper; but the addition of a vernier scale allows more accurateinterpolation, and is the universal practice; this is the vernier caliper.

Vernier, dial, and digital calipers can measure internal dimensions (using the uppermost jaws in the picture at right),external dimensions using the pictured lower jaws, and in many cases depth by the use of a probe that is attached tothe movable head and slides along the centre of the body. This probe is slender and can get into deep grooves thatmay prove difficult for other measuring tools.The vernier scales may include metric measurements on the lower part of the scale and inch measurements on theupper, or vice versa, in countries that use inches. Vernier calipers commonly used in industry provide a precision to ahundredth of a millimetre (10 micrometres), or one thousandth of an inch. They are available in sizes that canmeasure up to 72 in (1800 mm).[6]

Dial caliper

Mitutoyo dial caliper

Instead of using a vernier mechanism, which requires some practice touse, the dial caliper reads the final fraction of a millimeter or inch on asimple dial.

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In this instrument, a small, precise gear rack drives a pointer on a circular dial, allowing direct reading without theneed to read a vernier scale. Typically, the pointer rotates once every inch, tenth of an inch, or 1 millimeter. Thismeasurement must be added to the coarse whole inches or centimeters read from the slide. The dial is usuallyarranged to be rotatable beneath the pointer, allowing for "differential" measurements (the measuring of thedifference in size between two objects, or the setting of the dial using a master object and subsequently being able toread directly the plus-or-minus variance in size of subsequent objects relative to the master object).The slide of a dial caliper can usually be locked at a setting using a small lever or screw; this allows simple go/no-gochecks of part sizes.

Digital caliper

Digital caliper

A refinement now popular is the replacement of the analog dial with anelectronic digital display on which the reading is displayed as a singlevalue. Some digital calipers can be switched between centimeters ormillimeters, and inches. All provide for zeroing the display at any pointalong the slide, allowing the same sort of differential measurements aswith the dial caliper. Digital calipers may contain some sort of "readinghold" feature, allowing the reading of dimensions even in awkwardlocations where the display cannot be seen. Ordinary 6-in/150-mmdigital calipers are made of stainless steel, have a rated accuracy of.001" (.02mm) and resolution of .0005" (.01mm). [7] The sametechnology is used to make longer 8-in and 12-in calipers; the accuracy

for bigger measurements declines to .001" (.03mm) for 100-200mm and .0015" (.04mm) for 200-300mm. [8]

Many Chinese-made digital calipers are available very cheaply, and perform reasonably well. One point worthnoting is battery current and switching. Many calipers do not stop drawing power when the switch is in the offposition; they shut down the display but continue drawing nearly as much current. The current may be as much as20 microamperes,[9] much higher than for many established brands. Sometimes calipers may not work properlywhen the battery voltage has dropped relatively little; silver cells, preferably selected from a datasheet to have aconstant voltage for most of their life, may give a much longer usable life than alkaline button cells (e.g., SR44instead of LR44).[9] [10]

Increasingly, digital calipers offer a serial data output to allow them to be interfaced with a dedicated recorder or apersonal computer. The digital interface significantly decreases the time to make and record a series ofmeasurements, and it also improves the reliability of the records. A suitable device to convert the serial data outputto common computer interfaces such as RS-232, Universal Serial Bus, or wireless can be built or purchased. Withsuch a converter, measurements can be directly entered into a spreadsheet, a Statistical Process Control program, orsimilar software.The serial digital output varies among manufacturers. Common options are• Mitutoyo's Digimatic interface. This is the dominant name brand interface. Format is 52-bits arranged as 13

nibbles.[11] [12] [13] [14]

• Sylvac interface. This is the common protocol for inexpensive, non-name brand, calipers. Format is 24 bit 90 kHzsynchronous.[15] [16]

• Starrett[17]

• Brown & Sharpe[17]

• Federal• Mahr (appears to offer Digimatic, RS232, and USB)• Tesa[17]

• Aldi. Format is 7 BCD digits.[16]

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Like dial calipers, the slide of a digital caliper can usually be locked using a lever or thumb-screw.Digital calipers contain a capacitive linear encoder. A pattern of bars is etched directly on the printed circuit board inthe slider. Under the scale of the caliper another printed circuit board also contains an etched pattern of lines. Thecombination of these printed circuit boards forms two variable capacitors. As the slider moves the capacitancechanges in a linear fashion and in a repeating pattern. The two capacitances are out of phase. The circuitry built intothe slider counts the bars as the slider moves and does a linear interpolation based on the magnitudes of thecapacitors to find the precise position of the slider.

Micrometer caliperA caliper using a calibrated screw for measurement, rather than a slide, is called a micrometer caliper or, more often,simply a micrometer. (Sometimes the term caliper, referring to any other type in this article, is held incontradistinction to micrometer.)

ComparisonEach of the above types of calipers have their relative merits and faults.Vernier calipers are rugged and have long lasting accuracy, are coolant proof, are not affected by magnetic fields,and are largely shock proof. They may have both centimeter and inch scales. However, vernier calipers require goodeyesight or a magnifying glass to read and can be difficult to read from a distance or from awkward angles. It isrelatively easy to misread the last digit.Dial calipers are comparatively easy to read, especially when seeking exact center by rocking and observing theneedle movement. They can be set to 0 at any point for comparisons. They are usually fairly susceptible to shockdamage. They are also very prone to getting dirt in the gears, which can cause accuracy problems.Digital calipers switch easily between centimeter and inch systems.They can be set to 0 easily at any point with fullcount in either direction, and can take measurements even if the display is completely hidden, either by using a"hold" key, or by zeroing the display and closing the jaws, showing the correct measurement, but negative. They canbe mechanically and electronically fragile. Most also require batteries, and do not resist coolant well. They are alsoonly moderately shockproof, and can be vulnerable to dirt.Calipers may read to a resolution of 0.01 mm or 0.0005", but accuracy may not be better than about ±0.02 mm or0.001" for 150 mm (6") calipers, and worse for longer ones.[18]

Use

Using the vernier caliper

A caliper must be properly appliedagainst the part in order to take thedesired measurement. For example,when measuring the thickness of aplate a vernier caliper must be held atright angles to the piece. Some practicemay be needed to measure round orirregular objects correctly.Accuracy of measurement when usinga caliper is highly dependent on theskill of the operator. Regardless oftype, a caliper's jaws must be forced into contact with the part being measured. As both part and caliper are always to

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some extent elastic, the amount of force used affects the indication. A consistent, firm touch is correct. Too muchforce results in an underindication as part and tool distort; too little force gives insufficient contact and anoverindication. This is a greater problem with a caliper incorporating a wheel, which lends mechanical advantage.This is especially the case with digital calipers, calipers out of adjustment, or calipers with a poor quality beam.Simple calipers are uncalibrated; the measurement taken must be compared against a scale. Whether the scale is partof the caliper or not, all analog calipers—verniers and dials—require good eyesight in order to achieve the highestprecision. Digital calipers have the advantage in this area.Calibrated calipers may be mishandled, leading to loss of zero. When a calipers' jaws are fully closed, it should ofcourse indicate zero. If it does not, it must be recalibrated or repaired. It might seem that a vernier caliper cannot getout of calibration but a drop or knock can be enough. Digital calipers have zero set buttons.Vernier, dial and digital calipers can be used with accessories that extend their usefulness. Examples are a base thatextends their usefulness as a depth gauge and a jaw attachment that allows measuring the center distance betweenholes. Since the 1970s a clever modification of the moveable jaw on the back side of any caliper allows for step ordepth measurements in addition to external caliper measurements, in similar fashion to a universal micrometer (e.g.,Starrett Mul-T-Anvil or Mitutoyo Uni-Mike).

References[1] Mensun Bound: The Giglio wreck: a wreck of the Archaic period (c. 600 BC) off the Tuscany island of Giglio, Hellenic Institute of Marine

Archaeology, Athens 1991, p.27 & 31 (Fig.65)[2] Roger B. Ulrich: Roman woodworking, Yale University Press, New Haven, Conn., 2007, ISBN 0-300-10341-7, p.52f.[3] "hand tool." Encyclopædia Britannica from Encyclopædia Britannica 2006 Ultimate Reference Suite DVD .[Accessed July 29, 2008][4] Temple, Robert. (1986). The Genius of China: 3,000 Years of Science, Discovery, and Invention. With a forward by Joseph Needham. New

York: Simon and Schuster, Inc. ISBN 0671620282. Page 86–87.[5] Joseph Wickham Roe, English and American tool builders (1916) p. 203 (http:/ / books. google. com/ books?id=kw8LAAAAIAAJ&

pg=PA215& lpg=PA215& dq="Joseph+ R. + Brown"+ "vernier+ caliper"& source=web& ots=iEWHMoR6yj&sig=6Z9jCPivd_4CtL45ZMcCWhZODss& hl=en& sa=X& oi=book_result& resnum=3& ct=result#PPA203,M1)

[6] http:/ / www. starrett. com/ download/ 246_p108_114. pdf[7] www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=47257 6" Digital Caliper[8] http:/ / www. msi-viking. com/ digital_caliper/[9] Caliper Battery Life (http:/ / www. davehylands. com/ Machinist/ Caliper-Batteries/ )[10] Buying Button Cells for Digital Calipers (http:/ / www. truetex. com/ buttons. htm)[11] Mitutoyo 1715 (http:/ / www. mitutoyo. com/ pdf/ 1715. pdf), page 22.[12] Mitutoyo E4174-524 (http:/ / www. mitutoyo. com/ pdf/ E4174-542. pdf), page 33.[13] Don Lancaster, Tech Musings 145 (http:/ / www. tinaja. com/ glib/ muse145. pdf)[14] AllAboutCircuits (http:/ / forum. allaboutcircuits. com/ showthread. php?t=25147)[15] Shumatech (http:/ / www. shumatech. com/ support/ chinese_scales. htm)[16] Yadro (http:/ / www. yadro. de/ digital-scale/ protocol. html)[17] Don Lancaster, Tech Musings 142 (http:/ / www. tinaja. com/ glib/ muse142. pdf), page 142.3[18] Accuracy of calipers (http:/ / www. tresnainstrument. com/ accuracy_of_calipers. html)

External links• Animated Vernier calipers (http:/ / members. shaw. ca/ ron. blond/ Vern. APPLET/ )• RS-232 Interface Design Details For Digital Caliper (http:/ / www. compendiumarcana. com/ caliper/ )• How Digital Calipers work (http:/ / www. biotele. com/ digital_caliper. htm)• How Digital Calipers work (http:/ / www. yadro. de/ digital-scale/ working. html) at YADRO• Caliper interface with lcd and led (http:/ / rchobby. gmxhome. de/ elektro/ pic/ caliper/ calip_eng. htm)• B.C. Ames (http:/ / www. bcames. com/ main. html)• Adobe AIR application screen ruler based on a Vernier caliper (http:/ / www. adobe. com/ cfusion/ marketplace/

index. cfm?categoryid=6& marketplaceid=1& event=marketplace. offering& offeringid=10142)

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• Simulator of use and interpretation: Vernier caliper in millimeter, resolution of 0.05mm (http:/ / www. stefanelli.eng. br/ webpage/ en-vernier-caliper-pachymeter-calliper-simulator-millimeter-05-mm. html)

• Simulator of use and interpretation: Dial caliper in inch, resolution of 1/64in (http:/ / www. stefanelli. eng. br/ en/dial-caliper-pachymeter-calliper-simulator-fractional-inch. html)

• Simulator of use and interpretation: Digital caliper in inch, resolution of 0.0005in (http:/ / www. stefanelli. eng.br/ en/ digital-caliper-pachymeter-calliper-simulator-inch-one-thousandth. html)

Article Sources and Contributors 8

Article Sources and ContributorsCaliper  Source: http://en.wikipedia.org/w/index.php?oldid=420115186  Contributors: 10metreh, 4twenty42o, Abigail number 1, Aboalbiss, Alvesgaspar, Andrejj, Andrew c, Angr,ArséniureDeGallium, Atlant, Audionaut, Bobblewik, Bryancpark, Calicocatz, Coolhandscot, DARTH SIDIOUS 2, Danpeirce, Darren Foong, Davidbspalding, Demorphica, DennisIsMe,Dinferno, Diomidis Spinellis, Discospinster, Dysprosia, E Wing, Ecographer, Ed g2s, Ekboy, Epbr123, Erik Baas, Everyking, Falcon8765, GVnayR, Gargoyle888, GargoyleMT, Gene Nygaard,Glrx, Gonzalo Diethelm, Graibeard, GreyCat, Gun Powder Ma, Hacktivist, Honmingjun, Hooperbloob, Iampariah, J.delanoy, JForget, Java13690, Jebba, John Reid, Jóna Þórunn, Katieh5584,Kjlewis, KnightRider, Krawi, La Pianista, Leonard G., Lkinkade, Lookang, Luigizanasi, Lumos3, M.Colcher, MER-C, Mackin-pen, Mackinmfg, Mandarax, Mani1, Marchiks, Marek69,Markn951, MassimoAr, Mgiganteus1, Michael Daly, Michael Hardy, Mikeblas, Mmowat, Monkeyblue, Motorhead, Napalm Llama, PeaceNT, PericlesofAthens, Persian Poet Gal, Pfftpfftpfftpfft,Philip Trueman, Pichote, Playatown, Poiuyt Man, Pol098, Quality Measurement, R sirahata, RainbowOfLight, Reach Out to the Truth, Rich Farmbrough, Rjensen, RoyBoy, SF007, Samw,Slysplace, Someonesdad363616, Specter01010, Splarka, Srleffler, Stepho-wrs, Stevertigo, Streng-l, Stupidwhiteman, Tamariki, Tedickey, The Thing That Should Not Be, Three-quarter-ten,Trevinci, WikikiwiKW, WikipedianProlific, Wikipelli, Wizard191, Xofc, ZacBowlingAlt, Zs, 238 anonymous edits

Image Sources, Licenses and ContributorsImage:Messschieber.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Messschieber.jpg  License: GNU Free Documentation License  Contributors: User:ArtMechanicFile:Calibro archetto graduato.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Calibro_archetto_graduato.JPG  License: Public Domain  Contributors: User:TrevinciImage:InsideCalipers.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:InsideCalipers.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: User:graibeardImage:OutsideCalipers.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:OutsideCalipers.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: User:graibeardImage:DividerCalipers.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:DividerCalipers.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: User:graibeardImage:OddlegCalipers.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:OddlegCalipers.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: User:graibeardImage:Vernier caliper.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Vernier_caliper.svg  License: Creative Commons Attribution 2.5  Contributors: User:Alvesgaspar,User:ed_g2sImage:Dial calipers.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Dial_calipers.jpg  License: unknown  Contributors: SplarkaImage:DigitalCaliperEuro.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:DigitalCaliperEuro.jpg  License: Public Domain  Contributors: Original uploader was Xofc aten.wikipediaImage:Using the caliper new en.gif  Source: http://en.wikipedia.org/w/index.php?title=File:Using_the_caliper_new_en.gif  License: Creative Commons Attribution 2.5  Contributors:User:Alvesgaspar

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