ASME B89.1.7:2009 pdf download Performance Standard for Steel Measuring Tapes
4.9 Definition of the Calibrated Distance
The calibrated distance between graduations shall betaken as the intervals between the centerlines of pairsof graduations at the edge of the tape where the shortestgraduations appear.
In the absence of short graduations,the calibrateddistance is defined to be the intervals between center-lines of the graduations at the bottom edge of the tapewhen viewed with the numbers right side up. The dis-tance is defined at 20°C, when the tape is fully supportedwith specified tension (possibly zero) applied (seesection 6).
It should be noted that cases exist that are not coveredabove.In these cases the owner should specify the defini-tion of the calibrated distance. In the absence of a cleardefinition, the calibrating technician shall use his or herdiscretion in defining the calibrated distance, and thedefinition of the calibrated distance shall be documentedin the calibration report.
5 ‘STEEL MEASURING TAPES
This Standard applies to numerous tapes,as describedin paras.5.1 through 5.4.
5.1 Retractable Steel Tape Rule
A retractable steel tape rule is a graduated and num-bered flexible steel blade with either a curved cross sec-tion that provides a measurable degree of stiffness,ora flat rectangular cross section, with an end fitting andoptionally a spring motor within a case. It is to be con-structed in a manner that allows easy extension andprovides for quick retraction into the case.
5.2 Measuring Tape – Steel General Purpose
A steel general purpose tape is a graduated and num-bered flexible steel blade with an end fitting and a caseor reel having a winding drum and handle, or othermechanism, for retraction of the tape into the case.5.3 Measuring Tape – Surveying/Engineering
A surveying/ engineering tape is a graduated andnumbered flexible steel blade that may be fitted withclips at one or both ends to permit attachment of handlesand tensioning devices.It usually is attached to a reelhaving a winding drum and handle in such a way asto be easily removable.
5.4 Measuring Tape – Liquid Gaging
A liquid gaging tape is a graduated and numberedflexible steel blade with an end fitting to which a plumbbob is attached. Liquid gaging tapes are either innagetapes or outage tapes. The tapes are similar in designbut differ in their mode of use.
Innage tapes measure the depth of the product fromits surface to the tank bottom or datum plate. Therefore,the end (tip) of the plumb bob, when the tape is hungvertically, is the zero reference mark for an innage tape(see Fig.1).
Outage tapes measure the height of space above theliquid from a reference point on the tank to the surfaceof the product. The outage tape is lowered into the tankuntil the plumb bob breaks the surface of the liquid.The zero reference mark on an outage tape is locatedon the hook where the plumb bob is attached (see Fig. 1).
6CALIBRATION AND MAXIMUM PERMISSIBLE
ERRORS
6.1 Tension
Steel tapes with a flat rectangular cross section shall becalibrated while fully supported on a horizontal surfacewith tension applied as given in Table 1. Tapes witha curved cross section,regardless of length, shall becalibrated without tension.
6.2 Calibration Procedure
The measuring tape to be calibrated shall be laid outflat on a smooth horizontal surface and compared to alength standard whose uncertainty has been evaluated.Specified tension (possibly zero) shall be applied. Fric-tion between the surface and tapeline shall be mini-mized.If the comparison is between two tapes, acorrection for differential expansion of the materialsshould be applied.
For the most accurate results, the tape to be calibratedshould be tested against an interferometer system (seeNonmandatory Appendix B).The interferometer mea-surements shall be corrected for the environmentalconditions.
In all cases,the uncertainties associated with mea-sured errors shall be evaluated (see MandatoryAppendix I and Nonmandatory Appendices A and B).
6.3 Decision Rule Each length under test, L j , has a corresponding error, ? j , equal to the nominal value of the length, indicated on the tape, minus the measured value for that length. Each of these errors has an associated standard uncer- tainty, u( ? j ) (see Nonmandatory Appendix A or B). The index j p 1, 2, …, n, where n is the total number of lengths under test.
ASME B89.1.7:2009 pdf download
