Digital Balances: How to Read Specifications

Digital Balances are devices used to precisely measure the mass of an object. The design and inner workings of a digital balance will vary substantially between brands. To help you determine the difference between models and find the best for your needs, our scientists have compiled a list of the standard key terms and definitions you are likely to encounter in digital balance specifications.

Measurement Terms

Mass

Mass is the amount of matter in an object, and the mass of an object stays the same irrespective of location and gravitational forces. The SI unit of mass is the kilogram (kg).

Weight

Weight is the force exerted on an object by gravity, so the weight of an item will vary in proportion to the strength of the gravitational field. For example, you will weigh significantly less on the moon than on earth, but your mass will remain unchanged. The SI unit of weight is the same as that of force: the newton (N).

Digital Balance Terms

Capacity

Capacity refers to the maximum weight that a scale is capable of weighing.

Readability 

Readability designates the number of places after the decimal point that the scale can be read. As there is such a wide variety of digital balances available, readability between digital balance models can vary from 0.1g down to 0.0000001g!

Weighing Units

Weighing units refers to a digital balance’s measurement unit of output. Most commonly, you will see digital balance results expressed in units of mass; for example, grams(g), milligrams(mg) and micrograms (µg) along with other empirical units such as ounces (oz). Speciality balances will offer units specific to certain industries, for example, carats(ct), which are used to weigh gemstones and pearls.

Repeatability

Repeatability is the ability of a digital balance to display the same value when a weight is placed on it more than one time. You will often see repeatability expressed as a standard deviation.

Linearity

Linearity is the ability of a digital balance to display the correct value throughout the entire weighing range. Linearity ensures that your measurements will be consistent and precise as long as the weight is measured within the scale’s capacity and readability ranges.

The best way to describe linearity is with a graph. If you were to graph weighing results across the digital balances entire weighing range, you should get a reasonably straight line. See table 1 (below).

This graph example has a linearity of ±0.3g, so the actual results (orange) must remain between the permissible range of +0.3g (grey) and -0.3g (yellow) across the entirety of the scale’s capacity.

Actual results go above and below the perfect linearity line (blue) throughout the measurement range but, most importantly, at all times remain within the permissible range.

Calibration

Calibration is the procedure to make your digital balance display a specific value of a known standard mass.

Stabilisation Time

Stabilisation time is the time it takes for the digital balance to return a steady measurement. Stabilisation time is listed on device specifications as a ‘typical’ or ‘average’ time.

Sensitivity Drift

Sensitivity drift details how a digital balance’s measurement sensitivity will vary as ambient conditions change. Most commonly, you will see this specification term listed as “temperature sensitivity drift’, as the temperature is the most common environmental factor affecting digital balances.

Pan Size

Pan size is the size of the weighing platform.

Draft Shield

Draft shields are commonly found on analytical and microbalances. Shields protect against measurement disturbances such as drafts and air currents. (In indoor environments such as a lab, such disturbances are often produced by air conditioning systems).

Digital Balance Types

Analytical Digital Balance

Analytical Balances measure mass with an extraordinary degree of accuracy and precision.  Due to the precise nature of analytical balances, they have a high level of readability but a lower capacity.  Analytical balances often require draft shields (see above) to protect against measurement interferences.

Micro Digital Balance

While very similar to analytical balances, microbalances have even smaller capacities and even higher readability. Because of the high readability, micro digital balances are susceptible to static interference, drafts and vibrations. They often have additional features to a standard draft shield to help ensure stable measurements.

Precision Digital Balance

Whilst still very precise, precision digital balances have reduced readability and lower precision than analytical and microbalances. However, they have higher capacities and are less affected by environmental conditions. A wide range of body shapes and style options cater to various applications and offer users versatility and flexibility.

Certifications and Compliance

Good Manufacturing Practices (GMP)

Good Manufacturing Practices refers to guidelines set by agencies endorsed to issue authorisations and licenses affecting the manufacture and distribution of products in industries where health and safety issues are paramount, e.g. pharmaceutical products, food and beverage, cosmetics, and medical devices.

As many digital balances are deployed in the industries mentioned above, some products offer GMP data retention functionality to assist with compliance reporting requirements.

Good Laboratory Practice (GLP)

Good Laboratory Practice describes a quality management system commonly used in research laboratories, organisations and commercial environments to help ensure the consistency, reliability, reproducibility, and quality of products. As many digital balances are used in the abovementioned situations, some have GLP data retention functionality.

Trade Approved

Trade approved scales and balances are measuring devices approved by regulators or industry peak bodies for trade applications.

NMI

National Measurement Institute, Australia, is the measurement standards body of the Australian government.

CE

The CE marking on a scale is a certification mark that indicates conformity with safety, health, and environmental protection standards for products sold within the European Economic Area.

NRCS

National Regulator for Compulsory Specifications is an agency of the South African Government Department of Trade and Industry.

OIML

The Organisation International de Métrologie Légale (International Organization of Legal Metrology) is an intergovernmental treaty organisation based in France to promote the global harmonization of the legal metrology procedures (i.e., the application of legal requirements to measurements and measuring instruments).

NTEP

National Type Evaluation Program evaluates and certifies equipment before being offered for sale for trade use in the United States.

Conclusion

When purchasing a digital balance, having the definitions of critical terms you’ll encounter in the specifications at your fingertips will help you decipher the key terms affecting your choice of the best product for your needs and budget.

Need advice or assistance finding the best digital balance for your application? Speak with an Instrument Choice Scientist: Call 1300 737 871 or email [email protected].