Physics

# Examples Of Scales

Balances are instruments that measure the mass of an object, substance or living being and are used in laboratories, factories, shops, homes,  and hospitals. Its purpose is to indicate the mass of an object accurately.

What are they?

A balance is a lever that measures the mass of a body by establishing a balance between its mass and mass with standardized patterns. There are many types of scales depending on the applications and their precision.

Its main characteristics are versatility, precision, and sensitivity. Precision defines how accurate the results are, versatility and sensitivity establish the ability to repeat the same result by weighing the object multiple times.

Cross balance

It is the scale that represents justice and is known as the scale of saucers or classic scales. It has an axis or shaft that is crossed by two arms that hang two saucers at its ends and in the center a needle that indicates equality between the masses.

It establishes the mass by comparison between a known and unknown weight of the object to be measured. When equilibrium is reached, it means that the known masses represent the weight of the object.

Roman balance

It has two arms, but one is shorter than the other, balance is achieved with a lower comparison mass, but the weight is indicated by a needle in the center. The object to be weighed is placed on the longest arm and the mass to be compared on the shortest arm.

Roberval balance

The shaft rests on a resting point and has two plates at the end of each side. Compare the masses between the object and the known masses.

Spring balance

They are those that you normally find in a greengrocer, greengrocer or butcher. They can be mechanical or digital. They have a hanging plate where the object you want to weigh is placed. There are models in industries that can weigh up to tons.

Sliding Weight Balance

It has two known masses that move on scales, a macro, and a micro. We obtain the mass of the object or substance by placing them on a tray and sliding the macro scale first and then the micro-scale until obtaining the equilibrium position on the graduated arm. The point where the masses meet will indicate the mass of the object.

Kitchen scale

They are used to weigh the ingredients for a meal. They are exact because it is necessary to have the necessary amounts for a recipe to look good. Its capacity is reduced. They can be mechanical or digital.

Laboratory scales

They are scales that allow us to know the mass by sliding counterweights along a numbered scale. They can also be digital and are perfect for very small masses.

Ohr Balance – Westphal

It allows measuring the density of liquids. It has two arms, one shorter than the other. A weight is placed on the long arm and a thermometer on the short arm that goes into a glass container. This balance allows knowing the temperature of the liquid before measuring its density.

Types of scales

The scales are classified according to different aspects:

According to its minimum division:

Special precision balances: they have a minimum division of 0.001 grams or less. They may be:

1.Semi-analytical: it has a minimum division of 0.001 grams and weighs up to a maximum of 1 to 3 kg,

2.Analytical: it has a minimum division of 0.0001 grams and weighs between 100 and 300 grams maximum.

3.Semi micro-analytical: its minimum division is 0.00001 grams. It weighs a maximum of 10 to 30 g.

4.Micro-analytical: it has a minimum division of 0.000001 grams, it weighs a maximum of between 3 to 10 g.

5.Ultra micro-analytical: it has a minimum division of 0.0000001 grams, it can weigh a maximum of 1 to 3 g.

### Fine precision scales:

they have a minimum division of between 0.1 and 0.01 g. In this group we find:

Granataria: it has a minimum division of 0.1 g. It can weigh up to 30 kg.

Precision: its minimum division is 0.01 grams. It can weigh up to 10 kg.

Medium precision scales: they have a minimum division between 1 and 5 grams.

Ordinary precision scales: its minimum division is 5 grams or more.

## Depending on the operating system or its application:

Two-cymbal scales: they have two cymbals. In this group, we find the cross-scale and the Roberval scale. They usually work by the principle of balance, that is, the masses of the dishes are compared until the desired weight is obtained.

One-pan scales: They have a single pan. They work by sliding weights until the balance is achieved with the body in spite.

Roman scale: it has two arms of different lengths with hooks instead of saucers. In the short arm, you place the object to be weighed and in the long one the masses. The marks on the arms indicate when the object’s balance and weight were reached.

Platform scale: it has a platform where the object to be weighed is placed and some weights that move until the balance is achieved. Balance of greengrocer: it has weights that measure the weight of the product.

Pharmacy scale: it has mobile weights that move until the balance is achieved and an entrance to insert the coins and pay for the weighing process. Medical balance: they are the same as the pharmacy scales, but they do not have the system to pay with coins.

Baby scale: they have a surface to put the baby to bed and some weights that move to measure their weight.

Laboratory balance: they are high precision balances used in a laboratory. Mechanical analytical balance: to function they are based on mechanical principles.