Weights and Scales
The measurement of ingredients in processing is fundamental and it is important that the accuracy of the measurement
is fit for purpose, in other words, it meets the requirements of the application. However, every measurement is inexact
and requires a statement of uncertainty to quantify that inexactness.
Accurate measurement enables us to:
Maintain quality control during production processes
Calibrate instruments and achieve traceability to a national measurement standard
Develop, maintain and compare national and international measurement standards
Successful measurement depends on:
Accurate instruments
Traceability to national standards
An understanding of uncertainty
Application of good measurement practice
Weighing Scales are devices used to determine weight and are divided into two main categories: Spring Scales and Balance Beam Scales. Balance beam type scales are the oldest type and measure weight using a fulcrum or pivot and a lever with the unknown weight placed on one end of the lever, and a counterweight applied to the other end. When the lever is balanced, the unknown weight and the counterweight are equal. Spring scales were introduced in the 1760’s as a more compact alternative to the popular steelyard balance. Spring scales work based on the principal of the spring which deforms in proportion to the weight placed on the load receiving end. Strain gauge scales became popular in the 1960’s and used a special type of spring called a load cell. Strain gauge scales are the most commonly used in today’s market but electronic force restoration balances are used in laboratory and high precision applications. When discussing weights and scales, one question that often gets asked is “What’s the difference between accuracy and precision?”
For example, a scale with an IP-54 Rating is “Protected against dust and splashing water”. The “5” means that protection from dust is not totally prevented, but dust does not enter in sufficient quantity to interfere with satisfactory operation of the equipment. The “4” means water splashed against the enclosure from any direction shall have no harmful effect. The highest IP rating for a scale is an IP-69K Rating. This rating means that a strong water jet directed at the sensor from 4 directions must not have any harmful effects. A jet nozzle at 0°, 30°, 60° and 90° to the scale on a rotating table at 176° + 8°F, 4-6 inches away at 1250-1500psi. The test time is 2 minutes.