Mettler Toledo LJ16 Spezifikationen PDF herunterladen (Seite 26)

Chapter 3: General Considerations

Industry Standards

(12/99) 3-11

Industry Standards

There are several organizations that set standards for the scale industry and provide type

evaluation to ensure the accuracy of scales. In the United States, type approval is given

by the National Type Evaluation Program (NTEP), which is administered by the Office of

Weights and Measures of the National Institute of Standards and Technology (NIST). In

Europe, type approval is given by the European Economic Community (EEC) according

to recommendations set by the Organisation Internationale de Métrologie Légale (OIML).

United States Standards

NIST is part of the United States Department of Commerce. It sponsors the National

Conference on Weights and Measures (NCWM), an association of industry

representatives and federal, state, and local officials. This organization adopts uniform

laws and regulations recommended by NCWM members, and it publishes those

regulations in NIST Handbook 44. Adopted by most states and localities, NIST

Handbook 44 is the official listing of specifications, tolerances, and other technical

requirements for weighing and measuring devices.

Type evaluation is the procedure used to test a particular type (or model) of weighing

device. NTEP tests a sample of each model in a laboratory or in the field. If the model is

produced in various sizes and capacities, NTEP will evaluate a selection of these based

on the availability of sizes and capacities, the number of divisions, and the smallest

division size. If the tests show that the scale(s) complies with the applicable technical

requirements of NIST Handbook 44, NTEP issues a Certificate of Conformance for that

model of scale.

A Certificate of Conformance indicates that the particular scale tested by NTEP met NIST

Handbook 44 requirements, not that all scales produced meet the requirements. It is the

scale manufacturer’s responsibility to make sure that every scale of a certified model

meets the published specifications. Whether or not all models of an NTEP-certified scale

conform to NIST Handbook 44 specifications is solely up to the discretion of the

manufacturer. METTLER TOLEDO has procedural controls in place to guarantee that

every scale is produced according to the same specifications.

NIST Handbook 44 defines both acceptance and maintenance tolerances. Acceptance

tolerances must be met when the scale is first certified by NTEP. Maintenance tolerances

are twice as large as acceptance tolerances and apply after the scale has been installed.

Figure 3-6 shows NIST Handbook 44 acceptance tolerances for Class III scales.

1 2 ... 21 22 23 24 25 26 27 28 29 30 31 ... 197 198

Keine Kommentare

Mettler Toledo LJ16 Spezifikationen Seite 26