Weighing and proportioning

Weighing is the operation of determining the mass of any material as represented by one or more objects or by a quantity of bulk material. Proportioning is the control, by weighing, of relative quantities of two or more ingredients according to a specific recipe in order to make a mixed product, or to prepare the ingredients for use in a chemical process. 

It is likely that volumetric measures were used for quantity deterrnination when commodities were first bartered however, it has been established with certainty that weighing scales or balances have been in use for at least 7,000 years (1). Measuring by weight instead of by volume eliminates some very considerable inaccuracies from, for example, changes in specific gravity of liquids with temperature, or changes in density of solids owing to voids. 

Some common industrial weighing appHcations include the following  

Verifying quantities of incoming raw materials Controlling ingredients to the proper proportions 

Putting the product into packages of uniform weight, either by packaging direcdy on a scale or by using a scale to check the performance of filling equipment 

Weighing outgoing shipments for purposes of billing and deterniination of transportation charges Weighing interdepartmental material transfers for accounting purposes 

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H. Cohjn, Weighing and Proportioning of Bulk Solids, Trans Tech Pubhcations, Aedermaimsdorf, Swit2edand, 1975. 

Another anomalous property of some nickel—iron aHoys, which are caHed constant-modulus aHoys, is a positive thermoelastic coefficient which occurs in aHoys having 27—43 wt % nickel. The elastic moduH in these aHoys increase with temperature. UsuaHy, and with additions of chromium, molybdenum, titanium, or aluminum, the constant-modulus aHoys are used in precision weighing machines, measuring devices, and osciHating mechanisms (see Weighing AND proportioning). 

The weighing and proportioning of liquids and solids has also benefited from this technical revolution. Sensing devices and special-purpose computers give a level of precision and speed not possible in the era of elec tromechanical devices. The net result is that packaging and material handling systems now have the sophistication of chemical processes. 

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