AASHTO M231-95 pdf free download

AASHTO M231-95 pdf free download.Weighing Devices Used in the Testing of Materials.
4.2. accuracy—maximum permissible deviation of indications of a balance or scale from the true value within applicable tolerances.
4.3. balance—an instrument for determining mass, in its simplest form having a beam supported exactly in the middle and having two pans of equal mass suspended from its extremities. Generally, weighing devices of a relatively high degree of accuracy used for determinations of mass in the laboratory.
4.4. direct-reading halance—a balance on which the mass of applied loads of various magnitudes is either automatically indicated, or is indicated by means of a calibrated weighbeam. throughout all or a portion of the range of the balance.
4.5. equal-arm balance—a balance having a beam supported exactly in the middle, having two pans suspended from its extremities, in which the mass of unknown quantity on one pan is compared with a set of standards of mass in the other pan. There may or may not be a weighbeam.
4.6. general-purpose masses—standard masses used for general mass determination, generally being less accurate than standard analytical masses.
4.7. maintenance tolerance—maximum permissible deviation from correct indication for masses or balances in service.
4.8. off-center loading—application of a load to the pan of a balance or scale at a point displaced from the center of the support axis of the load-receiving element.
4.9. readabilTh’—the smallest unit of mass that can be read without estimation over the given range of measurement either directly or by use of a vernier or micrometer.
4.10. scale—an instrument or machine used for mass determination, usually embodying a system of multiplying levers. Generally considered to have a lesser degree of accuracy than balances.
4.11. sensitivity—mass required to produce a discernible movement in the indicating system of the balance or scale.
4.12. sensitivity requirement—the minimum change in the position of rest of the indicating element of a scale or balance in response to a specified change in test load on the load-receiving clement of the scale or balance.
4.13. simple balance—a balance designed primarily for use in conjunction with a set of standard masses. There may or may not be a weighbeam.
4.14. standard anal tical masses—working standards of mass used for analytical work, having relatively small tolerances from the stated values.
5. REQUIREMENTS
5.1. Analytical Balances—Analytical balances of the class specified shall conform to the requirements of Table 1. These requirements apply both to balances with built-in masses and balances used with separate masses. The class for standard masses is suggested to provide the required accuracy (Note 1).
Note 1The tolerances for standard masses are such that a single mass deviating by the full tolerance may cause the balance to exceed the accuracy requirement. In general, an individual mass will deviate only slightly from the stated value, and groups of masses will have some with a positive variation and some with a negative variation, which will tend to be compensating.
5.2. General-Purpose Balances and Sca/es—General-purpose weighing devices shall conform to the
accuracy, readability, and sensitivity indicated in Table 2. Within any interval equal to 10 percent
of the capacity of the balance, the difference in the load indications shall be accurate to within
0.1 percent of the difference in masses (Note 2). The device shall not be loaded in excess of its nominal or stated capacity.AASHTO M231-95 pdf download.