Every time an object is placed on a scale platform to be weighed the scale must be able to accurately measure the weight of the object and communicate the weight reading to the scale’s indicator—where the weight reading can be viewed. How scales manage to measure the weight of objects and communicate weight readings to the outside world varies, but electronic industrial scales typically manage to do this with transducer devices.
When an object is placed on the platform of an electronic scale, a transducer device will detect the amount of weight being applied to the scale platform and convert the measurement into an electronic signal. A microprocessor within the scale will then take the electronic signal, process it, and display a digital weight reading of the object on the scale’s indicator.
The Most Common Transducer in Electronic Industrial Scales
In electronic industrial scales, the most common type of transducer is the load cell. Load cells can be many different shapes and sizes, and they can be made from a variety of materials. For example, load cells are often made from aluminum because aluminum is inexpensive and easy to machine. Load cells made from aluminum are often used in low capacity scales, such as bench scales.
Load cells can also be made from steel. Steel is more durable than aluminum and capable of better resisting shock loading and overloading. Steel load cells are often used in floor scales and platform scales. Compared to stainless steel, another material used to manufacture load cells, steel is less expensive and easier to machine; however, in order to make steel load cells corrosion-resistant, they must be nickel-plated. This makes steel load cells not as rugged as stainless steel.
Stainless steel load cells are the most durable load cell option available for industrial scales. Although stainless steel is tougher to machine and more costly than aluminum and steel, stainless steel load cells are capable of resisting damage from corrosion, shock loading, and overloading better than load cells made from other materials.
Different Scale Technologies Utilizing Load Cells
Load cells can be made from different materials and the materials used can impact the longevity of load cells, but load cells can also be used differently. There are a number of diverse scale technologies in the weighing industry that manufacture and utilize load cells uniquely.
Strain Gage Technology
One of the most common scale technologies is Strain Gage. On Strain Gage scales, load cells are located under the scale platform and above the floor of the scale. Each load cell contains a spring element that attaches to each end of the scale floor and the underside of the scale platform. Inside the scale there are also strain gages—hence the name—which are wired together with the spring elements of the load cells. Together the spring elements and strain gages form what is known as the Wheatstone’s bridge. The “bridge” produces a voltage output that coincides with any resistance placed on the strain gages.
When weight is placed on the scale platform of a Strain Gage scale, the spring elements in the scale’s load cells bend. How much they bend is proportional to the weight of the object on the scale platform. The bending causes the bridge to bend, which changes the resistance of the gages. When the resistance of the gages changes, an analog signal is sent to the scale’s analog-to-digital (ADC) converter. The ADC then sends a digital signal to the scale’s digital indicator, where the weight reading can be read.
Strain Gage scales are generally accurate to 1/10 of 1%. This means they can produce measurements accurate within .1 pound of an object’s true weight if measured on a scale with a maximum capacity of 100 pounds. A deviation of .1 pound is not very significant for most companies; however, some companies require more accurate weight readings.
Surface Acoustic Wave Technology
Surface Acoustic Wave (SAW) technology was created by Arlyn Scales, a company recognized for high-quality design and scale manufacturing in the weighing industry for over 30 years. SAW technology shares a few similarities with Strain Gage technology, but the two technologies are in no way the same. For example, both technologies use load cells. But where Strain Gage scales measure strain and stress SAW scales measure displacement.
Scales made by Arlyn Scales containing SAW technology are called Ultra Precision Scales because SAW technology is capable of producing extremely accurate weight readings. Compared to the example above—where a 100-pound capacity Strain Gage scale produces an accuracy of 1/10 of 1%—a SAW scale with the same capacity produces results within 1/100 of 1%. How is it done?
Ultra Precision Load Cells
Load cells used in Ultra Precision scales are manufactured from stainless steel, which means they are less likely to be shock loaded or overloaded, and they are corrosion-resistant. Ultra Precision scales measure displacement instead of strain or stress, which means the load cells can be made from thicker metal (stainless steel).
In each stainless steel load cell there are 2 SAW transducers placed at opposing ends of the load cell’s spring element. The distance correlates with the amount of weight of the object on the platform. When weight is applied to the scale platform, the distance between the two transducers increases and a bulk wave is triggered. The wave is transmitted between the two transducers in a continuous loop, the frequency is measured digitally, and the weight reading is displayed on the scale’s digital indicator.
Ultra Precision scales by Arlyn Scales produce weight readings that are more accurate than other scale technologies and the scales are not easily influenced by airflow, temperature, or other operating equipment.
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In industrial scales that utilize load cells, load cells are a vital component of the scales. They must be able to accurately communicate the measurements of objects placed on scale platforms to scale operators—the proper operation of companies might just depend on it.
Learn more about all of the scales Arlyn Scales designs, manufactures, and sells by visiting our website today. On our website you can learn more about SAW technology and the benefits of Ultra Precision Scales too. Contact Arlyn Scales with any questions or comments by calling 800-645-4301 or fill out our online contact form.