4. The electrometer
“What can be done that’s any good if things can’t be reduced to degrees and measurements - specially in Physics?…”
In the strength of this conviction Volta adapted the electroscopes in current use and made linear and universal tension-measuring instruments: straw electrometers, using two pieces of straw instead of elder-wood pith balls. He also introduced a scale with zero in the middle.
To make measuring independent of the electrometers employed, Volta used an electrometric balance which exploited the force of electrostatic attraction between two plates at some distance from each other. The unit of tension is then defined as a function of the force of attraction.