In the world of measurement, accuracy is defined as how well the measurement’s result agrees with the true value of whatever is being measured.
In other words, if the actual amount is equal to the result of the measurement, the scale is perfectly accurate. There are different degrees or classes of accuracy:
Class I: Special (i.e. a high-precision balance)
Class II: High (i.e. a high-precision industrial scale)
Class III: Medium (i.e. a commercial scale)
Class IV: Ordinary (i.e. a high-capacity scale)
Accuracy means different things for different applications. Accuracy matters more when you want to minimize operating errors, or prevent overfill or underfill of a product. Product safety is also a consideration, as is weighing speed and when you weigh two products of varying weights on the same scale.
Many confuse precision with accuracy. Precision measures how well repeated measurements of the same quantity agree. If you weigh a 10mg amount an infinite amount of times, and you get the same result each time, your scale is perfectly precise. In another way, precision can be expressed as repeatability.
Precision is important when you want stable and reproducible production. If you want your batches to have similar quality, you want a precise pharmaceutical scale. Also, you can reduce operating errors by ensuring you get the same weight no matter what area of the scale the product is placed.
Note that a highly-precise scale isn’t necessarily a highly-accurate scale.
The resolution of a scale is the weighing range of the scale divided by the display readability.
Resolution can be likewise defined as capacity divided by readability. High-quality pharmaceutical scales are both accurate and have high resolution. These resolutions are certified by institutes of Weights & Measures; a certified resolution (also known as “approved resolution”) makes a scale legal for trade.
Note that high readability delivers a high resolution, but doesn’t necessarily result in high accuracy.
Resolution matters when you want to reduce weighing errors, control for ambient conditions like temperature, wind, and vibrations, and make sure your scales are legal for trade.
Finding the right pharmaceutical scales depends on what you need between accuracy, precision, and resolution.