All About the Types of Balances and Scales!

by Trevor Neve

Balances and scales have dated back to Ancient Egypt, used for trading goods. A simplistic equal-arm balance on a fulcrum was often used to compare two weights. Today, scales are much more complicated and have a multitude of uses, which range from laboratory weighing of chemicals, to weighing of packages for shipping purposes. Scales are used all around us!

Analytical Balance 

Most often used in a laboratory, or in settings where extreme sensitivity is required. Analytical balances are so sensitive, they can even be affected by air currents. They measure mass, which is useful in chemical analysis as the results are not based on gravity at a specific location - which would affect the weight. Precision and accuracy in these balances often exceeds one part in 106 at full capacity, which generally ranges from 1g to a few kg. The delicate internal devices are protected by a beam arrest, which prevents damage when objects are being placed or removed from the pan. The pan is the area on the balance where objects are placed. The balance is brought to the reference position with adjustable leveling feet. The reference position is determined by the leveling bubble, the spirit level, or plumb bob - an integral part of the balance. A draft shield protects against air currents affecting the measurement. This is a plastic or glass enclosure that allows access to the pan.
The A&D HR-100 is our best selling analytical balance

Equal Arm Balance / Trip Balance

Much like the iconic trade scales of ancient Egypt - but modernized. This scale incorporates two pans, placed on opposite sides of a lever. There are two different ways to use this type of scale. The object to be weighed is placed on one of the pans, and standard weights are added to the opposite pan until they are balanced. The sum of the weights is equal to the mass of the object. The second application is to place 2 items on each scale and adjust one side until they are leveled. This is helpful in applications such as balancing tubes or centrifugation where two objects must be the exact same weight.

Platform Scale

This type of scale uses a system of multiplying levers, and allows heavy objects to be placed on a load bearing platform. The weight is transmitted to a beam, which is balanced by moving a counterpoise. The counterpoise is an element of the scale that acts to counterbalance the weight on the platform. This type of scale is used for weighing drums of product, or even weighing animals - for example at a vet's office.
The A&D FG-150KBM is our best selling platform scale

Spring Balance

This balances uses Hooke's Law - stress in the spring is proportional to the strain. Spring balances have a highly elastic helical spring, made of hard steel suspended from a fixed point. The weighing pan is attached at the lowest point of the spring. When it is loaded up, an indicator shows the weight measurement, with no manual adjustment. We often see these scales in the produce section of the grocery store.

Top-Loading Balances

This balance is primarily used in a laboratory setting. They can measure objects weighing around 150g - 5000g. While they offer less readability than an analytical balance, they allow measurements to be made quickly as most are electric, and offer a digital readout in seconds, making it a convenient choice when exact measurements are not required. Top-Loading balances are also more economical than analytical balances.

The A&D FX-120I is our best selling top loading balance

Torsion Balances

Often, microbalances and ultra-micro balances, which weigh fractional gram values, are torsion balances. Measurements are based on the amount of twisting of a wire or fiber, with a common fiber type being quartz crystal.

The A&D BM-20 is our best selling microbalance.

Triple-Beam Balance

Less sensitive than a top-loading balance, triple beam balances are often used in a classroom situation because they are easy to use, durable, and economical. They have three decades of weights - usually in gradations of 100g, 10g, and 1g - that slide along individually calibrated scales. These scales offer less readability, but are useful for many weighing applications.

This Triple Beam Balance is perfect for use in schools

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