Final answer:
The insulation resistance tester is known as a megohmmeter. It measures high resistances using Ohm's law to ensure the effectiveness of electrical insulation.
Step-by-step explanation:
The device that is also called an insulation resistance tester is the megohmmeter. Ohmmeters, including megohmmeters, are used to measure resistance. They apply a known voltage to a resistance, measure the resulting current, and then use Ohm's law (V = I x R) to calculate and display the resistance. A megohmmeter, or insulation resistance tester, specifically measures high resistances that regular ohmmeters cannot accurately measure, which is important when testing the insulation of electrical wiring and components.