ASTM E1951 PDF

A number in parentheses indicates the year of last reapproval. Reflected light microscopes areused to characterize material microstructures. Many materialsengineering decisions may be based on qualitative and quan-titative analyses of a microstructure. It is essential that micro-scope magnifications and reticle dimensions be accurate. It is recommended that the stagemicrometer or scale used in the calibration should be traceableto the National Institute of Standards and Technology NIST or a similar organization. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.

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A number in parentheses indicates the year of last reapproval. Reflected light microscopes areused to characterize material microstructures. Many materialsengineering decisions may be based on qualitative and quan-titative analyses of a microstructure. It is essential that micro-scope magnifications and reticle dimensions be accurate.

It is recommended that the stagemicrometer or scale used in the calibration should be traceableto the National Institute of Standards and Technology NIST or a similar organization. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Referenced Documents2. Significance and Use4. For a precise determinationof the magnification observed through an eyepiece, see theprocedure describe in 5.

An expression for the total magnification isshown in Eq 1. Mt5 Mo3 Me3 Mi 1 5. Mt5 First, photograph the stage micrometer using thedesired combination of objective, bellows extension, zoom andintermediate lens, and then measure the apparent ruling lengthon the photomicrograph. The measurement should be madeconsistently from an edge or center of one division to thecorresponding edge or center of another see Note 1. Bydividing this apparent length of ruling by the known dimensionof the micrometer, the magnification of the photomicrograph isdetermined see Fig.

The accuracy of the calibration isdependent on the accuracy of the calibrated stage micrometerand the scale used to measure the apparent length of thephotographed ruling. NOTE 1—The choice of using the edge or center of a reticle line dependson the method of manufacture used to produce the measuring device.

Some devices are calibrated from center to center while others aremeasured from one edge to another. Consult with the manufacturer todetermine which method should be employed. Current edition approved Nov. Published December Originallyapproved in Last previous edition approved in as E—02 United States A rule was overlaid. From one corresponding edge of adivision to another, using the rule, a distance of 62 mm wasmeasured over a known distance of 0.

Dividing 62 mm by 0. Mechanical play in thesedevices can be a significant source of error. Focus an image of a stage micrometer onthe screen, and then measure the projected apparent length ofthe ruling.

If convenient, the measurement can be madedirectly on the screen, or by transferring the apparent length toa scale using pinpoint dividers. Virtually all modern computermonitors use square pixels, so the x horizontal and y vertical magnifications are the same provided that the monitor isdisplayed in its native resolution.

If the monitor screen reso-lution is set to other than its native resolution, the magnifica-tions may be different between the x and y axes and result in adistorted image. The measurement should be made consistentlyfrom an edge or center of one division to the correspondingedge or center of another.

The magnification is calculated bydividing the measured apparent length by the known dimen-sions of the micrometer see Example 2 in 5. Overlay theeyepiece micrometer image on the stage micrometer image,with one end of each coincident upon one another. Themeasurement should be made consistently from an edge of onedivision to the corresponding edge of another Fig. Theeyepiece reticle calibration can be determined by dividing theknown length of the stage micrometer by the number ofoverlaid eyepiece micrometer divisions.

This calculation yieldsa length per division value of the micrometer for a givenoptical setup. Eighty-five divisionswere counted over a distance of 0. The length per division can then be calculated asfollows. Also,the positioning of the reticle in the eyepiece must be repeatable.

NOTE 3—Caution must be observed if both eyepiece tubes are adjust-able. Also, change in interpupillary distance may change themagnification, particularly in older microscopes. NOTE 1—This schematic shows the procedure used to determine the calibrated magnifications of video screens, video printers, projection screens, andphotographs.

This procedure will require a stage micrometer withhigh contrast markings. Acircular projection of the lightwill appear. Initially, the size of the beam will decrease until the eyepointdistance is reached, then at a distance greater than the opticaleyepoint, the size of the circular projection will increase.

The calibration measurement can thenbe made directly on the ground glass or on the developed filmor resulting print. The calibration is completed by placing thedivisions of a rule coincident upon the projected image of thestage micrometer. The alignment should be made consistentlyfrom an edge of one division to the corresponding edge ofanother. A large-format bellows camera, without lens, may beconveniently used here. If this is done, a film of the image canalso be exposed, with the calibration then performed on thedeveloped film.

NOTE 1—This schematic diagram illustrates the procedure used to calibrate an eyepiece measuring reticle. Next, a distanceof mm was measured perpendicular from the plane of theeyepiece. The divisions of a rule wereplaced coincident upon the projected image of the stagemicrometer consistently from an edge of one division to thecorresponding edge of another.

A distance of 89 mm wasmeasured over a known distance of 0. By dividing the measured length by the knownlength a calibrated magnification of 99X was determined.

Themoveable cross-hair in the eyepiece is positioned at an extremeend of a stage micrometer coincident with one micrometerdivision. The measurement should be made consistently froman edge or the center of one division to another.

Traverse the cross-hair over as many micrometer divi-sions as possible that are visible in the central region of thefield of view. Note the new micrometer drum value. To obtainthe total drum movement, subtract the final drum value fromthe initial value.

The value of each increment on the filar drumis determined by dividing the actual length traversed on thestage micrometer by the total drum movement. Repeat thisprocedure for each objective of interest.

This calculation issimilar to that of determining an eyepiece micrometer calibra-tion Example 3 in Section 5. NOTE 1—A schematic diagram illustrating the procedure used to determine the magnification observed through the microscope eyepieces. Traverse the stagemicrometer as described in the previous section. If the mea-sured distance is incorrect, adjust the multiplier accordingly.

Reset to zero, and traverse the stage micrometer again. The filareyepiece measured 17 The multiplier was then determinedby dividing by 17 The resulting multiplier is 0. Next, the accuracy of the multiplier was checked. First, thesystem was zeroed, then the multiplier 0. The filar eyepiece measured

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First, photograph the stage micrometer using the desired combination of objective, bellows extension, zoom and intermediate lens, and then measure the apparent ruling length on the photomicrograph. The measurement should be made consistently from an edge or center of one division to the corresponding edge or center of another see Note 1. By dividing this apparent length of ruling by the known dimension of the micrometer, the magnification of the photomicrograph is determined see Fig. The accuracy of the calibration is dependent on the accuracy of the calibrated stage micrometer and the scale used to measure the apparent length of the photographed ruling.

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ASTM E1951 PDF

There were no books found for the applied search filters. Are you sure you want to empty the cart? This standard is not w in any packages. Print 1 2 3 4 5 page sstarting from page current page. It is essential that microscope magnifications and reticle dimensions be accurate.

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