What is a Dynamometer

A dynamometer is a device designed to measure the force and weight of objects from the elasticity of a spring or elastic spring. The word is formed from the Greek term dynamis meaning ‘force’, and the term meter (metron) meaning ‘measure’.


Mechanical dynamometer and electronic dynamometer

Among its functions is:

  • Measurement of body weight;
  • Application in testing machines (measure penetrations of hardness, tensile strength, etc.);
  • Measure applied forces.

The traditional dynamometer was invented by Isaac Newton. This scientist applied the principles of Hooke’s law of elasticity, according to which the stretching of a certain flexible or elastic material is directly proportional to the force exerted on it.

Originally, the dynamometer works with a hook at the lower end on which the object whose force or weight is to be measured is hung. Today there are scales that use this spring system, but they replace the hook with plates on which the objects are placed, which is why there is a tendency to confuse dynamometers with balances.


Operating mechanism of the dynamometer and the
scales that also apply Hooke’s law.

parts of a dynamometer

A dynamometer is made up of the following parts:

  • A spring or spring;
  • A cylinder that houses the spring;
  • Two hooks, each one distributed to each end of the dynamometer:
    • A hook that serves as a support or enclave;
    • A hook on which force or weight is exerted;
  • A scale of measurement in newtons, kilograms, or both.


Dynamometer Types

There are at least two types of dynamometers: mechanical and digital. Let’s see each of them.

  • Mechanical dynamometer: These are traditional dynamometers, along the same lines as the one developed by Newton, based on a totally mechanical system. This dynamometer does not require power for its operation. It usually offers greater precision, since its difference range is just 0.3%.
  • Digital or electronic dynamometer: are those in which digital measuring instruments are used. Their mechanism is much more complex and they require energy sources for their operation, such as batteries or electric current.
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Difference Between Dynamometer and Balance

The dynamometer and the balance are different instruments, although they are often confused. The dynamometer measures the force and weight of objects while the balance measures only their mass. Certainly the weight is related to the mass of the object, but it varies according to the gravitational field while the mass does not.

Balances and dynamometers have different operating systems. Balances are artifacts with two equal arms that work by placing masses at each of their ends, which allows their physical properties to be determined by comparison (weight and mass).


From left to right: column balance, Roberval balance and Bérarger balance.

The dynamometer, on the other hand, determines the force and/or weight of a singular object, which is nothing more than the force with which the object is attracted by the gravity field. If gravity (the force) changes, the weight changes. Therefore, the dynamometer must be calibrated every time it is moved, unlike the balance.

All weight measurement systems based on springs or elastic springs are actually dynamometers. All measuring systems that work by mass counterweight are balances.

See also: balance, force, gravity, properties of matter, and weight.