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Advancing Justice Through DNA Technology
Balances
Home > Forensic Biology > Laboratory Orientation > Use of Basic Equipment > Balances
Measurements
The common meaning of weight is mass, and mass is the amount of matter in an object. Mass and weight are equal at sea level. According to the International System of Units (SI), the unit of weight for mass is kilograms (kg). According to the National Institute of Standards and Technology, weight may be considered synonymous with mass in common parlance, and the SI unit of the quantity weight is the kg.02
A discussion and demonstration of the use of all types of balances in the laboratory, such as top-loaders and analytical balances, should be provided. If necessary, a review of basic math and standard measurements can be presented. Traceable standards, such as weight sets, are easily obtained for this purpose, or a laboratory may employ an outside entity to conduct the calibration. It should be noted that the outside entity must use traceable standards to conduct the calibration. A balance should be calibrated whenever it is moved.
Top-loading Balances
Top-loading balances are generally portable and ideal for easy weighing tasks. They have a larger weighing pan and may offer ranges such as 210g x 0.01g and 8100g x 1g, and are thus applicable for weighing chemicals to make stock reagents, etc. It is imperative that anyone using a balance know how to properly use features such as the external calibration and taring functions.
Analytical Balances
Analytical balances offer higher resolution and measuring quality, in ranges typically to 2.1g x 0.001mg and 510g x 0.1mg. Such tools are necessary in the preparation of some reagents in the forensic biology laboratory.
