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Precision balance: characteristics, functions, parts, uses

Below is one of the hundreds of models that can be found on the market for this type of scale. Note that unlike the analytical balance, in the precision balance your weighing pan is not enclosed in a glass capsule, but protected by a lid.

A small precision balance measuring the mass of a piece of paper. Source: Your Best Digs via Flickr (www.yourbestdigs.com)

Precision balances are often called precision scales. This is due to the superior exposure of its single plate, which is reminiscent of the scales used to weigh food, bags of cement, people, loads of raw materials, and even vehicles.

History

The symbol of the two-plate balance has been known for thousands of years before the birth of Christ. The civilizations of that time could not determine the absolute mass of the objects they traded, or their wealth, but only the relative masses; that is, they used a reference standard and observed which objects weighed more than that.

It was not until the arrival of the industrial age, at the end of the 18th century, when the British Richard Salter invented a scale that related the weight of objects to the tension experienced by the spring. Thus the spring balance was born.

As the years passed, the instruments were separating and differentiating themselves into scales and scales. Another important step took place in 1900 with the appearance of the short-beam analytical balance, by the Sartorius company.

This was then followed by the Mettler Toledo company, which in 1945 had first introduced the single-plate model and its own scale governed by the principle of substitution.

Finally, in 1973, Mettler launched the first precision electronic balance, PT1200, being the model that started the evolution of this type of balance.

Red beaker on precision balance. Source: Davidmimay / CC BY (https://creativecommons.org/licenses/by/4.0)

Visuals

Anyone with a scale on hand will know what a precision balance looks like. Practically, they are the digitized, miniaturized and most accurate version of the scales. Such products are often confused with each other and the dividing line between them is not clear.

The weighing plate or pan is usually round, although in many models it has a square shape, as if it were a heating plate. This is in the upper part of the balance, which is why in English it is called top-loading balances , or top-loading balance .

Capacity

The capacity, that is, how much mass the precision balance can measure, is highly variable, depending on the model and its applications. Therefore, there will be scales that resist more weight than others. Generally speaking, the small ones have a capacity of 200 g. Instead, there are some that measure in the order of kilograms.

Stability

An advantage of precision balances is that they are more stable or less “delicate” than analytical balances. They are less sensitive to the environmental conditions that surround them: humidity, temperature changes, unevenness in the surface where they rest, among other factors.

As a consequence, fewer considerations are taken when weighing with this instrument, making the operations easier and faster.

Precision

They are less accurate than analytical balances. However, because of their much higher capacity, their accuracies of 0.1 to 0.001 g (± 0.1 g or ± 0.001 g) make them extremely accurate instruments for the amounts of mass they carry.

Relative cost

Precision balances are cheaper or cheaper than analytical balances for the reasons stated above. In industry, outside of raw material or quality control laboratories, they are often preferred over analytical balances.

Precision Balance Features

The main function of a precision balance, like any other balance, is to determine the amount of mass of an object by means of variations of electrical signals. Another function that is coupled to this is to tare; without it, it would be necessary to perform the subtractions (or subtractions) of the masses to determine the difference we are looking for.

When the mass of an object is tared, the balance “erases” its mass for the moment and it is as if it weighs absolutely nothing. In this way, an empty container is tared, to remove its mass, is filled, and the reading of the mass will equal that of the content discharged into the container.

This is a very frequent procedure regardless of the end use or the spaces where the weighing is carried out. This is because the object to be weighed should never directly touch the balance plate, as it would stain or damage it, which is why the container where the object will be placed is almost always used and tared.

Parties

Plate

Stainless steel surface where the object whose mass is to be measured is placed.

Screen

Where the numbers and the balance commands are displayed.

Adjustment feet

They are a kind of screws or platform that allows the balance to be leveled.

Board

Composed of keys with different functions. Using the dashboard you can change the reported mass units from grams to kilograms, or tare the containers.

Applications

They are mentioned below, and finally, some examples of use of the precision balance:

– In the low-scale synthesis of some polymers and chemical compounds, it is used to measure the mass of the reactors and thus determine the mass of the final product at the end of the reaction

– Coffee beans, whole or ground, as well as coffee pots and cups, are weighed with this scale to keep track of the quality of the coffee served

– In the pharmaceutical industry to measure the mass of raw material

– Soil, sand, rock, grease or concrete samples can be weighed with this scale

– In jewelry, for the diamond and gem scale

– In the kitchen, to prepare a more rigorous recipe

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