Scale Technology

The scale industry has traditionally offered two major technologies, “Strain Gage” and “Force Restoration” (also known as “Force Motor”).

Strain Gage scales are the most widespread. They are also the least expensive. Typically, the resolution is 1:5,000 (1 part in 5,000). So a scale with a capacity of 50 lb will have a resolution of 0.01 lb. Likewise, a scale with a capacity of 100 lb will have a resolution of 0.02 lb. Premium scales will stretch this to 1:10,000. Recently, with the advent of modern electronics and compensation schemes, some vendors have offered much higher resolution. But actual accuracies have remained fairly similar, so very little is gained.

The majority of Strain Gage scales use load cells made out of aluminum. This helps keep the cost down, because aluminum is relatively inexpensive, and easier to machine into the required shapes. Higher end scale will choose to use plated steel, and the premium units will use stainless steel. This tends to provide increased ruggedness and durability.

“Force Restoration” scales use the principal of an electromagnet force opposing the weight on the scale platform. This has the advantage of very high resolution and accuracy ranging from 1:50,000 to 1:150,000 or even higher. It has disadvantages that include some temperature instability and drift, and difficulty in implementing in scales with capacities of 50 lb and greater. It can also be prone to damage from overload and shock loading. Perhaps the greatest disadvantage is the cost, which can range from four times to more than ten times the cost of strain gage scales.

Arlyn Scales has recently introduced into the market a superior, third technology, Surface Acoustic Wave, or SAW scales. This internationally patented system incorporates similar technology to that used in fabricating semiconductor integrated circuits to produce an extremely precise digital output. Resolution and accuracy are in the 1:100,000 to 1:150,000 range. The large load cell block is extraordinarily rigid, providing a very high level of overload and shock tolerance. Amazingly, the cost is in the range of high end strain gage scales.