SM0486

LESSON 5.

WEIGHTS AND BALANCES

AIPD Subcourse Number SM0486...........Mechanical

and

Electro-Mechanical

Measurement Principles

Lesson Objective.......................Given learning objectives and supportive

text you should be able to answer all

exercise questions pertaining to mass and

its measurements, and the analytical (micro)

balance with no error.

Credit Hours...........................One

TEXT

1.

INTRODUCTION

The training information in this chapter is a continuation of your training in

the areas of length, mass, and time measurements. This chapter is designed to help

you increase your knowledge of the principles applied when weights and balances are

used in mass measurements.

A review of mass measurement principles is combined

with construction and operation principles to help you become proficient at your

job. The sections in this chapter teach the fundamental theories of mass and its

measurements; construction and operation principles for bullion balances; metric

analytical balances, and the weights associated with each type of balance.

2.

MASS AND ITS MEASUREMENT

a. The mass of an object is a measure of its inertia.

Inertia is usually

defined as that general property of matter which causes a body in motion to remain

in motion or a body at rest to remain at rest unless acted upon by an external

force.

Any discussion on mass and balances must also include a discussion of

weights, since in our gravitional environment any mass always exhibits the property

of weight.

The relationship between mass and weight is so inseparable that mass

determinations by means of comparing unknown weights to reference standards are

referred to as "weighing processes."

b. Mass Standards.

The metric standard of mass in the kilogram.

Smaller

units are used in the measurements you perform. Mass standards similar to the one

in Figure 1 are generally called weights.

The National Bureau of Standards, in

order to identify weights as to their general precision, stability, and use, has

set up classifications for different weights. Although not mandatory, this scheme

has found wide acceptance in commerce and industry. Weights, as described by NBS,

are divided into four basic classifications, which are:

(1) Precision Laboratory Standards.

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