Accuracy is the most important quality for scales and so there are methods for testing and calibrating weighing equipment. The accuracy requirements for scales can vary widely depending on their purpose. For example, scales used to weigh livestock and large equipment generally have lower accuracy requirements. In comparison, scientific scales used in research laboratories typically require exceptionally high resolution and precision.
Our ultra-precision equipment utilizes surface acoustic wave (SAW) technology to provide accuracy and resolution. This accuracy lies in the 1:100,000 to 1:200,000 range.
Take a moment to think about what this figure represents in terms of real-world numbers. That represents an increase of some 10 to 20 times improvement of accuracy versus traditional standard strain gage scales. That’s due to the fact that Arlyn Scales’ engineers used groundbreaking technology that’s drastically different.
Some technicians have pointed out that these numbers are close to what you’d expect from a comparably sized magnetic force restoration scale, at a considerably lower cost. Some studies have suggested that SAW scales will actually outperform even this technology. The developments have created an entirely new collection of fans of the equipment from a variety of sectors.
Regardless of what kind of technology you prefer, however, you’re certainly going to want to consider a handful of metrics that are useful for judging equipment.
Resolution Vs. Precision Vs. Accuracy
When considering scales, three main qualities determine whether they are working properly, the first of which is resolution. Resolution is the value that tells the user how close the scale can read to the object’s true weight. For example, a scale may have a resolution of one gram. What this means is that if an object weighs 20 grams, then the scale will give a reading for the object up to one gram either way from the object’s true weight.
Precision differs from accuracy because accuracy is needed once, precision is needed all of the time. If you weigh the same object repeatedly but get different measurements each time, then the scale has low precision. On the other hand, if you get the same reading every time you weigh the object, then you have perfect precision.
However, precision does not equate to accuracy. For example, if the resolution of the scale is low, even with perfect precision, it will not give you the true weight of an object. In order to have high accuracy, the scale must have both high resolution and high precision.
In fact, it’s possible to create an extremely precise scale that will never return the true weight of an object laid on it. In the past, some retail scale vendors would actually go around bragging about the quality of admittedly bad scales. The reason was, simply, precision on them was really high in spite of all the other metrics being low.
Technically, those kinds of claims don’t constitute false advertising since the person making them isn’t claiming anything that’s untrue. Rather, they’re merely withholding information to make their products look better than they are.
Don’t fall into that kind of trap. Make sure that you’re working with a legitimate vendor that has experience in the field. While you’re at it, learn a little more about why scales may not be as accurate as they initially look to be.
Why Scales May Not Be Accurate
Over time, scales can lose accuracy due to plain old wear and tear due to regular use and age. Scales must maintain their original balance for accuracy. Over time, however, they tend to lose this balance and they will require recalibration.
Electronic scales may suffer malfunction in the circuitry over time that can cause loss of accuracy. Even new scales may become inaccurate in certain conditions especially in extreme temperatures. For this reason, the most accurate scales will have high-temperature stability.
Additionally, new scales may lose accuracy in rough conditions especially when equipment is subject to vibration and jarring. In outdoor, industrial and similar environments, it is necessary to clean weighing equipment to maintain accuracy, especially for high precision work.
Eventually, scales even get dirty and potentially corroded. Cylinder scales should be made from a durable material like stainless steel, for instance. Those that aren’t will eventually start to suffer if they’ve been repeatedly exposed to fluids in the course of work. Those who work under certain specific conditions will also find that moisture levels in their home business community will cause similar problems.
For instance, think about a cosmetics facility that has to maintain a certain humidity level. This will surely start to eat away at scales that aren’t designed to remain durable against all odds. In some cases, only the most durable scales could ever be safely used anyway. This is because of of the presence of hazardous materials in a work environment.
You may want to learn how to test a scale. That way you won’t have to worry about whether or not any particular weighing device is showing the right weight.
How To Test A Scale
For scales that don’t require high precision, it is possible to use objects with known weights to test the scales. Dumbbells are one such example. Although the weight of a dumbbell is not that accurate, it will suffice for these purposes.
The scale must be on a flat and level surface for testing. Start by setting the scale so that it reads zero. For manual scales, you may need to turn a wheel or screw that adjusts the reading. Once the equipment reads zero, place the object with a known weight on the scale.
If the reading is not accurate, adjust the scale to get the correct weight of the object. Digital scales may have calibration options that allow adjusting of the reading. If the scale does not provide any option for calibration, then you can still use the scale. You will have to compensate, however, by correcting measured weights using the error factor.
To test the precision of the scale, it is necessary to repeat the test several times. Evaluate whether the result is the same or nearly the same. If the readings are widely different, then the scale has low precision.
Repeat the test at different times during the day and at different temperatures. Factor in the curvature of the planet itself and the presence of elevated or lower humidity levels. These could actually interfere with readings.
You won’t normally need to consider these issues when working with any piece of weighing equipment in a production environment. Nevertheless, you’re going to want to at least consider them if you’ve been thinking your scale is giving really strange readings.
Fortunately, scales from Arlyn come already calibrated so you won’t have to worry about these and other related issues. You might not even need to conduct a test of a well-made scale.
Testing Precision Equipment
Scales used in scientific, engineering, manufacturing and similar types of operations often require extremely high accuracy. For such testing, it is necessary to use certified calibration weights instead of more common objects like dumbbells.
A good method is to use three weights with a ratio of about 1:2:4. Also use a sum that represents a substantial percentage of the scale’s capacity. Start off by zeroing the equipment as in the process mentioned above. Then begin measuring weights to see whether they produce the same results consistently, as this will test for precision.
To test accuracy, weigh the calibrated weights in different combinations. Then see if the results represent the correct sums of the weighted objects. These procedures measure the linearity of the scales. A taring test determines whether the linearity tests continue to produce the same results when the scale resets to zero or to a non-zero calibration.
When conducting testing of high accuracy scales, use a room with a controlled temperature. For some equipment, the internal temperature of the equipment is also important. Additionally, weighing equipment can be sensitive to static electricity and radiofrequency or electromagnetic interference.
The term ‘drift’ describes inaccuracies caused by environmental factors like temperature and static electricity. For equipment used in conditions in which these variables are not controllable, then it will be necessary to measure the sensitivity drift of the scale.
Manufacturers provide temperature ranges for their equipment along with calibration certification in some cases. Note that calibration certification not might be valid if the equipment comes from a distant location. For devices that require high accuracy, even differences in geomagnetism and barometric pressure can result in measurement differences when compared to the equipment calibration location.
The frequency of calibration will depend on how important accuracy is to the operation. Another important factor is the conditions that might cause the equipment to lose accuracy. Some organizations may recalibrate weighing systems on a monthly basis. Others conduct testing at the start of each shift or even before each use of the equipment.
Test Our Aryln Scales Technology
We use an internationally patented technology known as Surface Acoustic Wave (SAW) scales that provide extremely high resolution and accuracy. The techniques used are similar to those employed to manufacture integrated semiconductor circuits. SAW scales have high-temperature stability and the load cells are rigid with excellent overload and shock tolerance.
As a result, we can offer users certain pieces of gear that they wouldn’t be able to find anywhere else otherwise. Interested parties are invited to contact us through our online form and tell us more about their scale-related challenges. We’ll make sure to find them a piece of equipment that can help them get the job done.