|Pocket voltmeter made in the USA circa
1925 for battery voltage measuring used in the early radio
|Primitve galvanometer made in France
|In reality the modern
electrical measuring instrument always followed the scientific
and technological development. Thus, the Electric- measuring
concept started firstly with the researches of the physicist
Charles Columb. Columb invented an instrument known as the Columb
pendulum that through the same he established the fundamentals
laws of the Electricity. Later, the Danish physicist H. C. Oersted,
to establish the relation between Electricity and Magnetism
used the same laws. The consequences of such experiment were
very important to the Electrical science as in 1820 the french
scientist André Ampère proved by a series of new
experiments that all the magnetic effects mentioned by Oersted
could be produced by the electric current alone. He demonstrated
the important fact that two parallel wires carrying electric,
attract each other when the current flow in like directions,
and repel each other when they flow in unlike or opposite directions.
He proved that the force of attraction and repulsion is directly
proportional to the strength of the currents, and inversely
proportional to the square distance between them.
Following Arago invented the first electro-magnet by flowing
a current through a wounded wire over a core of soft iron. At
this time, in England Faraday was studying the magnetic field
produced by different types of circuits.
Around 1823 Ampère built the first measuring instrument
known as galvanometer whose term was originated from the name
of the famous Italian phycisist Luigi Galvani. In this way,
through this instrument now the intensity of the current could
be measured accordingly.
If the measurement instruments originated from the evolution
of the electromagnetism were so important, certainly the development
of the osciloscope was the major contribution of Electronics
in the field of measurement of the electrical parameters.
The electron bean generated in the cathode ray tube can be compared
to the pointer of the galvanometer used in a classic measurement
instrument, but now actuating as an indicator in such away the
variations of the measured quantities could be followed in very
The osciloscope can be used as a recorder also.Nowadays, the
modern osciloscope used in several electronic fields is the
technological evolution whose roots was the Braun tube invented
in1897, several years before the appearance of the first thermionic
valve; later known as cathode ray tube. The Braun tube was also
the origin of the modern TV screen.