The analytical balance is the common piece of equipment in the scientific laboratory. These highly precise instruments can measure down to ten thousandths or even hundred thousandths of a gram. The triple beam balance is a type of scale that uses counterweights on a three rider beams to counterbalance the sample in the pan. On the other hand, modern analytical balances use a complex system of electronic sensors to accurately mass a substance. The analytical balance is so sensitive that it often has a draft shield to prevent air currents from interfering with the measurement. When weighing, a weigh boat or weigh paper is used to hold the substance being weighed and protect the weighing pan. Before weighing a substance, analytical balances are tarred to subtract the weigh boat or weigh paper and re-zero the scale. Tarring refers to setting the scale back to read zero and allows for a substance to be accurately weighed. Aside from weighing chemical substances, analytical balances are used to animals or insects, and centrifuge tubes in ultracentrifugation experiments.