Over the last few decades, industrial scale technology has become stagnant. Strain gage load cells have been the predominant technology. However, these scales may not be as precise as some industries require. When strain gage scales are not capable of providing the necessary measurements, magnetic force restoration scales are used. However, these scales are much more expensive than strain gage scales and do not have the capacity to weigh extremely large loads without additional support.
We have recently introduced scales that incorporate Surface Acoustic Wave technology into their design. With an accuracy equal to that of a force restoration scale, Surface Acoustic Wave scales are available at a much lower cost, similar to that of a strain gage scales.
Standard Scale Technologies
Strain Gage Scales
For the last sixty or so years the most popular scales have been those with strain gage technology. Strain gage load cells have been the standard for typical industrial scales. A type of resistor, an aluminum or steel spring is used to produce a measurement. Weight is determined by how far the spring bends when a load is placed on it, or the resistance of the spring to the weight of the load.
However, these scales may not provide the most accurate readings for several reasons, including the adhesive used to place the spring in the scale. This is because the spring has a tensile quality, while the adhesive used doesn’t, which ultimately affects the overall flexibility of the spring and its ability to generate an accurate reading. Also, the spring must be placed with extreme precision. A strain gage load cell is designed to detect vertical forces, but there are also horizontal forces that it must reject. It’s positioning within the weighing device is imperative to manage these different forces accurately.
As with any other resistor, strain gages are affected by changes in temperature, which alters their resistance capacity. While technology has been created that attempts to compensate for this change, load cell output will still vary with temperature. Generally, a strain gage scale has an accuracy of about one tenth of one percent and a resolution from one part in five thousand, with the capacity to reach one part in ten thousand.
Force Restoration Scales
With a higher accuracy and resolution than a strain gage scale, force restoration scales consist of a system that utilizes electromagnetic technology that supports the weighing platform, which must be directed by a precise flexure system. The electromagnetic current necessary to counteract the weight on the platform is directly proportional to the weight of the load. An accurate weight measurement is determined by assessing the amount of current necessary to offset the load.
However, the flexure system that directs the platform is prone to damage due to side forces and shock loading. Shock loading occurs when a large weight is dropped suddenly upon a platform, which can damage a scale’s components.
Another disadvantage of force restoration scales is their inability to weigh loads with larger capacities without the incorporation of a mechanical support. Because the amount of current rises in proportion to the weight of the load, the current required for a large capacity load would become prohibitive. This means that a force restoration scale, while more accurate than a strain gage scale, is also more sensitive and often costs three to five times more than its strain gage counterpart.
The Arlyn Scale Solution: Surface Acoustic Wave Technology
Distinguished by their high accuracy, our Surface Acoustic Wave (SAW) scales are a cost effective, yet extremely accurate, weighing solution for many industries that have struggled to find a scale that suits their exact requirements.
Rather than measure the amount of strain in the spring element, SAW scales measure the amount of displacement using transducers, resulting in strain levels that are less than ten percent of those found in strain gage cells, making readings more accurate.
A transducer is a device that converts between two different kinds of energies, in this case, converting pressure into an electrical signal. The substrate material of the transducer is a crystalline structure composed of lithium niobate, through which a bulk wave runs. The wave is created by a metalized pattern that acts as a transmitter. The wave travels the length of the transducer and generates an equivalent signal on a second, parallel substrate.
A second metalized pattern on the latter substrate acts as a receiver. The signal received by this substrate is amplified and fed back to the transmitter. The distance between the transmitter and receiver and the frequency of oscillation between the two determines the displacement of the spring element.
Compared to strain gage scales, which offer only an accuracy of one-tenth of one percent, a SAW scale provides an accuracy of one one-hundredth of one percent, making it extremely more accurate — the equivalent of a force restoration scale. SAW scales are about five times more rugged than strain gage scales because the strain levels of the load cell are extremely low and are as much as ten to twenty times more rugged than force restoration scales, making them the most suitable option for harsh industrial environments.
Scales with Surface Acoustic Wave technology, while being as accurate but more rugged than a force restoration scale, are only about one third the cost. While slightly more expensive than strain gage scales, they are also much more accurate and durable, able to withstand the high usage and harsh atmosphere of many industrial environments.
Arlyn Scales is a manufacturer and distributor of weighing devices for a variety of industries. Made in our Long Island warehouse, we ship our products factory direct, cutting out the middleman that drives up our competitors’ prices. We never buy foreign and rebrand because we prefer to monitor the quality of our products at home, ensuring that you receive the most accurate, rugged, and efficient tool to manage your operation.
Browse our selection of high accuracy scales to find one best suited to your needs. If you cannot find a scale that meets your requirements, please don’t hesitate to contact us as we can craft a custom option at an affordable price. We can be reached at (516)593-4465 .