Insulation resistance is the resistance value of an insulator and represents its insulating property. Materials that conduct electricity easily, such as copper and aluminum, are called conductors that have very low resistance values. On the other hand, materials such as rubber and glass which are difficult to conduct electricity, are called insulators (non-conductors) that have extremely high resistance values.

As for electrical equipment and electronic circuits, electricity flows through the electronic circuits, but in unnecessary areas, electricity must be stopped flowing. Not only will the circuit not work as intended, but there is a risk of short circuits, electrical leakage, and electric shock. Therefore, proper insulation must be provided by using insulators.

The insulator measures insulation resistance to check for insulation defects, that is called insulation resistance measurement. In this method, a dedicated megger insulation tester is used because the resistance value to be measured is very high.

Insulation testers are used by switching between ranges for low and high voltages. With an insulation resistance tester, a high voltage is applied to the object to be measured, and the resistance is determined from the flowing current.