SOLUTION

• Secondary instruments can be classified according to the effects of electricity they utilize.
• Secondary instruments can be classified based on the effects of electric current or voltage that their operation depends on.
• These effects include magnetic, heating, chemical, electrostatic, and electromagnetic induction.
• For example, ammeters and voltmeters can utilize the magnetic or heating effect, while DC ampere-hour meters use the chemical effect.
• The classification of secondary instruments can also be based on their function (indicating, recording, or integrating) or the kind of current they measure (AC, DC, or AC/DC)