Aggregates are everywhere we look in the world around us. These materials, which are made up of an aggregate of different other materials, including various types of stones, clay, silt, and sand, include the asphalt that paves our roads, the concrete that is used for the foundations of our skyscrapers, or the cement that makes up the bricks of our homes. There is no single aggregate-each one is made differently for a different purpose. One aggregate that uses a certain mixture of stones, silt, and petroleum-based binding may have very different characteristics than one that uses another mixture of pebbles, clay, and a different binding. One aggregate may be more suitable for roads while another may be more suitable for sidewalks.

On any construction site, construction managers must ensure that the aggregate they are using, whether concrete or asphalt, meets the specifications necessary for the job. Therefore, at set intervals of time, the team must carry out a compositional analysis of the aggregate. The aggregate is poured into a sieve with large holes that will only block the largest pieces of stone from falling through. Following this, it is poured into sieves with consecutively smaller and smaller holes until each component of the aggregate is in its own sieve. Then, the sieves and their contents must be weighed with an electronic scale. The total percentage of each material is calculated and compared with the necessary standards.

It is necessary to measure the composition of each aggregate very accurately. This becomes particularly difficult when each component may weigh up to 100 pounds. A standard digital scale may only be able to weigh each component to .01 pounds, which is not precise enough. One scale company, Arlyn Scales, has developed ultra-precision electronic scales that use Surface Acoustic Wave (SAW) technology for aggregate testing. These industrial scales are rugged enough to withstand the force of aggregate components while being able to weigh each component to .001 pounds.

Digital scales manufacturers have had a choice of two prevalent technologies. The most common has been industrial scales that use one or more strain gage type load cells. Smaller bench scales and parts counting scales use a single load cell mounted in the center of the scale platform. Larger platform scales and floor scales use one load cell under each corner of the scale platform. Depending on the size of the scale platform, intermediate sized scales, such as cylinder scales and drum scales may use either a single load cell or four. The accuracy of this type of scale is quite good, often delivering error levels of only one tenth of one percent. Using modern electronics, some of the other error terms, such as temperature effects and non linearity, have been improved with smart algorithms. But there is still a limit of accuracy that cannot be exceeded.

The second technology is known as force restoration. Industrial scales using this method can achieve accuracy levels up to twenty times better than strain gage electronic scales. Unfortunately, the cost is generally two or three times higher.

Arlyn Scales has invented a third technology for precision scales called Surface Acoustic Wave scales. Semiconductor transducers provide digital weight values that are equal to force restoration, but at costs that are similar to strain gage digital scales. These precision scales are also much more rugged than the other technologies.