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.
| |
Best Strain Gauge |
Force Restoration |
SAW |
| Resolution |
1:10,000 |
1:150,000 |
1:150,000 |
| Repeatability |
1:10,000 |
1:100,000 |
1:100,000 |
| Linearity |
1:10,000 |
1:60,000 |
1:60,000 |
| Creep |
1:5,000 |
not reported |
1:40,000 |
| Sensitivity Drift |
20 ppm/C
(5° to 35°C) |
3 - 10 ppm/C (10° to 35°) |
3 ppm/C
(-10° to 55°C) |
| Battery Operation |
Optional |
No |
Optional |
| Overload (Ruggedness) |
~150% rated Capacity |
~150% rated Capacity |
> 500% rated capacity |
| Cost |
100% |
400%-500% |
100% |
|
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Questions?
 Check our
FAQs page, or to speak to our highly trained scale professionals, call Monday through Friday from 8am to 5pm EST at 800.645.4301. You can also
e-mail us or fax your request to 516.593.4607 anytime.
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