Only conductor resistance can be measured with a multimeter
Conductor/Insulator
Conductor: an object that conducts electricity well
Insulators: objects that conduct electricity poorly (note, not objects that do not conduct electricity)
Common conductors in our life are: copper, iron, aluminium, gold, silver, graphite, etc.
Common insulators in our life are: plastic, rubber, glass, ceramics, pure water, air, various natural mineral oils, etc.
Here we should pay special attention to is that the insulator is poor conductivity of the object, not non-conductive objects. Strictly speaking, absolutely non-conductive objects do not exist. Plastics, for example, can be punctured at higher temperatures and thus conduct electricity. Therefore, insulators are classified into five grades according to their heat-resistant temperature: Y, A, E, B, F, H and C.
Similarly, insulators may be punctured at higher voltages and thus conduct electricity. Therefore, the insulator
Whether the conductor is relative to a certain voltage, the voltage is called the insulator's rated voltage.
According to reason, whether the wire burns and the voltage does not have much to do. Then why does he still have to mark the rated voltage? This is because the wire outside the insulating skin has a voltage tolerance range. We can simply understand that when the water pressure exceeds the range of the water pipe, then the pipe will be destroyed, the water inside will spray out. Similarly, when the voltage of the wire more than the range of insulation skin, wire insulation will be destroyed, the current will run out, commonly known as "leakage".
A multimeter actually uses Ohm's law to measure resistance. We all know that when measuring resistance, the multimeter is powered by 1.5V and 9V batteries. When the two pens are connected to the resistor, the current in the meter starts from the positive terminal of the battery, then passes through the meter head, the resistor, and then returns to the negative terminal of the battery. Based on the current size of the meter head, you can judge the resistance size, because the voltage is certain, the current size depends on the resistance size.
For measuring the resistance of a conductor, this is perfectly fine; but for measuring an insulator, it won't work, because whether the insulator conducts or not depends on the voltage and temperature. For example, an insulator at 9V is not conductive, so when measured with a multimeter, the meter naturally has no current through the head, so the display resistance is infinite. But if you continue to apply a higher voltage, it may be breakdown conductive. So when measuring whether an insulator is conductive or not, a voltage is specified.
