ASME B89.4.19:2021 pdf free download

ASME B89.4.19:2021 pdf free download Performance Evaluation of Laser-Based Spherical Coordinate Measurement Systems
1 scOPE
This Standard prescribes methods for the performance evaluation of laser-based spherical coordinate measurementsystems and provides a basis for performance comparisons among such systems. Definitions, environmental require-ments, and test methods are included with emphasis on point-to-point length measurements.The specified test methodsare appropriate for the performance evaluation of a majority of laser-based spherical coordinate measurement systemsand are not intended to replace more complete tests that may be required for special applications.
This Standard establishes requirements and methods for specifying and testing the performance of a class of sphericalcoordinate measurement systems called laser trackers.’ A laser tracker is a system that directs the light from a range-measuring device to a retroreflecting target (called a retroreflector) by means of a two-axis rotary steering mechanismwhile monitoring the angular position of these rotary axes, thereby forming a spherical coordinate metrology system.Such a system may measure a static target, track and measure a moving target, or measure (and perhaps track) somecombination of static and moving targets. This Standard can also be used to specify and verify the relevant performancetests of other spherical coordinate measurement systems that use cooperative targets, such as laser radar systems.This Standard focuses specifically on the use of laser trackers as industrial measurement tools rather than on their usein surveying or geodesy.Specified tests are designed to evaluate the staticpoint-to-pointlength measurement capabilitiesof these systems. The specified tests are not intended to evaluate the dynamic performance of the laser trackers. Addi-tional tests are included thatevaluate the range measurement capability oflaser trackersequipped with absolute distancemeters(ADMs).The tests do notevaluate workpiece thermal compensation capability and are notsensitiveto sphericallymounted retroreflector (SMR) imperfections.
2 INTRODuCTION
ln addition to providingfor the performance evaluation oflaser trackers,this Standard facilitates performance compar-isons among different systems by unifying the terminology and the treatment of environmental factors. lt defines testmethods appropriate for evaluating the performance of a majority of laser trackers, but it is not intended to replace morecomplete tests that may be required for special applications.
Systems that have passed the performance evaluation tests of this Standard are considered capable of producingtraceable point-to-point length measurements for the conditions required herein.Application of point-to-pointlength measurements to a specific workpiece or measurement task may require additional testing and analysis inorder to establish metrological traceability.This Standard provides technical guidance that may be useful in the cali-bration of laser-based spherical coordinate systems for point-to-point length measurements.
The Appendices describe various factors that should be considered when using this Standard.
(a) Mandatory Appendix l discusses metrological traceability, with particular focus on demonstrating traceability ofreference lengths used in laser tracker performance evaluation.Requirements for demonstrating metrological trace-ability are presented per ASME B89.7.5.
(b) Nonmandatory Appendix A discusses the traceability of laser tracker point-to-point length measurementsperformed subsequent to a system passing the performance evaluation tests described in this Standard.
(c) Nonmandatory AppendixB describestests and procedures for determininggeometricerrors in the construction ofSMRs so that the suitability of a particular SMR for laser tracker performance testing can be evaluated.
(d)Nonmandatory Appendix C describes environmental factors that influencethe refractive index oflight in air.Thesefactors affect the wavelength oflight and should be carefully understood before proceeding with the testsdescribed in thisStandard.
(e) Nonmandatory Appendix D describes four methods that can be used to establish a calibrated reference length forpoint-to-point length measurement system tests.Uncertainties in realization of such lengths are discussed.Nonmandatory Appendix D also describes the measurement capability index and the simple 4:1 acceptance decisionrule used to accept or reject laser tracker performance evaluation test results.
f) Nonmandatory Appendix E describes the effects of spatial temperature gradients on laser beam propagation.Equations are derived for radial errors due to speed-of-light variations and angular (or transverse) errors due tobeam refraction. A numerical example illustrates the use of the formulas.
(g) Nonmandatory Appendix F describes a number of interim tests that can be used to quickly assess laser trackermeasurement performance in the interval between more complete performance evaluations.
This Standard prescribes performance evaluation tests that may be used by laser tracker manufacturers to generateperformance specifications. These specifications are stated as the maximum permissible error (MPE) allowed for eachtest under specified environmental conditions.