The history and technology of weighing
by Bill Wedderburn, chairman
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The history and technology of weighing by Bill Wedderburn, chairman |
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Instrumentation and Weighing: the history and technology of weighing
The ability to weigh and measure was one of themajor developments of early civilization and has since grown into one of man's most sophisticated skills. In this article. Bill Wedderburn brings us up to date on an area of technology which is vital to our modern way of life.
The history of standardization in weighing and measurement is itself a study in the history of the civilization of man. Earliest historical evidence shows man using barter as the means of exchange; avoiding the need to weigh merchandise in exchange for money. However, with the growing permanency of dwellings, and the slow evolution of village and city living, measures of length establishing property and territory began to emerge.
One of the earliest systems for measuring length was developed around the Mediterranean. The basis of this system was the cubit, the Egyptian hieroglyphical symbol of the forearm. This length was measured from the point of the elbow to the tip of the middle finger. Overcoming the problem of varying lengths of men's forearms, each ancient civilization standardized one customary length for its particular cubit and maintained it to around ± 2%.
The Royal Egyptian cubit (524mm) was divided into 7 palms (74.9mm) and 28 digits (18.7mm). It was the Egyptian cubit which evolved to form the general Mediterranean standard, and both the Greek and Roman imperial measures were based upon the Egyptian.
Around 3000BC the Northern Cubit, which was thought to have originated in the Orient, became widely adopted. This measure was used from that time onwards in Egypt, North Africa, North India and China. Following imperial conquest and Teutonic migration, this standard (with some minor local variants) was adopted as far as Germany, England and Ireland.
The Northern Cubit, under the direction of the Roman general and administrator Drusus (38BC - 9AD) who adopted the measure from the localpeople under his control, became the virtual standard unit for all land measurement through to the mid-nineteenth century. The Drususian foot measured 333mm, 37mm longer than the Roman foot o< 296mm.
The English yard, known as the Imperial System was defined by Statute in the fourteenth century and continued in use until the mid-nineteenth century from where it has been gradually replaced with the metric system.
Unlike linear measurements which first evolved in ancient Egypt, the earliest recorded commercial use of weighing (for weighing gold and silver) was 2500BC. In early Egypt, historical evidence shows commerce to have been by barter, removing the need to measure by weight and exchange for currency. The first use of the balance scale in ordinary trade has been dated to 1300BC. Prior to that date, balances were only used for weighing gold.
The earliest beam balances had a capacity of 6.5g and a sensitivity of 0. 13g and beam balances with a 130g capacity had a sensitivity of 1.95g. The eight standards of weight used by the ancient civilization of the Middle East each evolved from the shekel. Shekel standards ranged from 7.78g (Palestine) to 14.13g (Phoenician). The larger units only evolved over time as there were no early commercial applications for weighing. These larger weights were known as minas and comprised 25,50 or 60 shekels.
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Crane
scales are now available with remote (wireless)
digital weight display which enables operators
to weigh large difficult-to-handle items from the crane
hook and have the digital weight display beside them
for easy reading and convenience.
Semi-micro electronic balances suitable for laboratory and factory offer readability down to 0.01 mg and capacities up to 200g. A convenient feature of these balances is a simple touch key which can change the weight system from grams to metric carats (CM), ounce troy, piece counting and percentage determination. Electronic digital force measuring instruments which can be hand-held or mounted in a test stand are suitable for tension and compression testing in capacities from 500g to 500kg. These accurate and easy-to-use test instruments greatly assist industry to improve quality control in production. Compact electronic sensors have allowed the design of low profile digital platform scales. These machines are available in niatform size typically ranging from 200 X 1200mm to 1800 X 1800mm. Weighing capacities range from 600 through to 6000kg. One of the main advantages of these scales is that the low profile platform height and the use of optional ramps provide for easy movement of trollies, etc on and off the platform.
Previously, platform scales were installed in pits so that the platform was flush with ground level. These pits collected water and foreign matter and caused "housekeeping" problems. Modem scales now no longer need pits in the floor and if fitted with fork lift ramps can be conveniently moved to any area in the factory in which the scale is needed.
An interesting development in weighing technology is the light weight low profile portable truck wheel and axle weigher. Although the scale has a weighing capacity of lO,OOOkg it weighs only 14.5kg and has a platform height above ground level of 15mm. This instrument is most convenient for weighing vehicles in remote areas.
What of the future of weighing and measurement? It is very hard to guess exactly which direction or directions it will take. With electronics we are only limited by man's imagination and with the constant research and development being carried out the future shall be very exciting. However, whatever the technology of the future, the words of John Quincy Adams ring true:
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