ASME B89.4.19 pdf download

ASME B89.4.19 pdf download.Performance Evaluation of Laser-Based Spherical Coordinate Measurement Systems.
ASME B89.4.19 prescribes methods for the performance evaluation of laser-based spherical coordinate measurement systems and provides a basis for performance comparisons among such systems. Definitions, environmental requirements. and test methods are included with emphasis on point-to-point length measurements, The specified test methods are appropriate for the performance evaluation of a majority of laser-based spherical coordinate measurement systems and are not intended to replace niore complete ests that may be required for special applications.
This Standard establishes requirements and methods for specifying and testing the performance of a dass of spherical coordinate measurement systems called laser trackers) A laser tracker is a system that directs the light from a rangemcasuflng device to a retroreflecting target (called a retroreflector) by means of a two-axis rotary steering mechanism while monitoring the angular position of these rotary axes, thereby forming a spherical coordinate metrology system. Suds a system may measure a static target, track and measure a moving target, or measure (and perhaps track) some combination of static and moving targets. This Standard can also he used to specify and verify the relevant performance tests 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 use in surveying or geodesy. Specified tests are designed to evaluate the static point-to-point length measurement capabilities of these systems. The specified tests are not intended to evaluate the dynamic performance of the laser trackers. Additional testsare included thatevaluate the range mcasurementcapabilityof lasrrtrackersequippcd with absolutedistance meters (ADM5). The tests do not evaluate workpiece thermal compensation capability and are not sensitive to spherically mounted retroreflector (SMR) imperfections.
2 INTRODUCTION
In addition to providing for the performance evaluation of laser trackers, this Standard facilitates perlormance comparisons among different systems by unifying the terminology and the treatment of environmental factors. It defines lest methods appropriate br evaluating the performance of a majority of laser trackers, but it is not intended to replace more complete tests that may be required for spectal appllcatiens.
Systems that have passed the performance evaluation tests of this Standard are considered capable of producing traceable point-to-point length measurements for the conditions required herein. Application of point-to-point length measurements to a specific workpiece or measurement task may require additional testing and analysis in order to establish metrological traceability. This Standard provides technical guidance that may be useful In the calibration 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 I discusses metrological traceability, with particular focus on demonstrating traceability of reference lengths used in laser tracker performance evaluation. Requirements for demonstrating nietrological traceability are presented per ASME B89.75.
(b) Nonmandatory Appendix A discusses the traceability of laser tracker point-to-point length measurements performed subsequent to a system passing the performance evaluation tests described in this Standard,
(c) Nonmandatory Appendix B describes tests and procedures for determining geometric errors in the construction of SMRs so that the suitability of a particular SMR for laser tracker performance testing cats be evaluated.
(d) Nonmandatory Appendix C describes environmental factors that influence the refractive index of light in air. These factors affect the wavelength ofleght and should be carefully understood before proceedingwllh the tests described in this Standard.
I-i GENERAL TRACEABILITY ISSUES
This Standard employs the interpretation of traceability described in ASME B89.7.5-2006. Two issues of traceability arise in the testing and subsequent use of laser trackers. The first issue is that If a perlormance evaluation is conducted on a particular laser tracker, then, in order to demonstrate that the system meets the manufacturer’s specifications, the reference lengths must satisfy the traceability requirements of section 1-2. This provides the connection to the SI deilnition of the meter and allows a comparison of the measured length errors with the specified maximum permissible error (MPE) values.
One of the traceability requirements is for documentation traceability. This is a requirement to describe how the connection to the SI definition of the meter Is achieved. For example, If a scale bar is employed to realize the reference length, then the documentation traceability is the calibration certificate of the scale bar to an appropriate metrological terminus. If the reference length is realized using the laser interferometer internal to the laser tracker (I FM), then this I FM must have metrological traceability to an appropriate metrological terminus (see sectIon 1-3).
The second issue of traceability is that if the laser tracker is to be used for subsequent point-to-point length measurements (e.g., by a user in a factory), then the requirements of ASME B89.7.5 must be fulfilled for the measurements to be considered traceable (see Nonmandatory Appendix A).