Megger: An Overview

A Megger is a specialized electrical instrument used primarily for measuring very high electrical resistances, commonly known as insulation resistance. It is an essential tool in electrical engineering for testing the quality and integrity of electrical insulation in cables, motors, generators, and other electrical equipment.

Megger's Core Function as a Mega-Ohmmeter

The term "Megger" is actually a brand name that has become synonymous with this type of insulation resistance tester. Its primary function is to measure resistances that are extremely high, typically in the range of mega-ohms (\(10^6\) ohms) or even giga-ohms (\(10^9\) ohms). To do this, a Megger applies a high DC voltage across the insulation and measures the minuscule current that flows through it. According to Ohm's Law (\(R = V/I\)), the resistance is then calculated.

Because the resistances it measures are in the mega-ohm range, the most accurate and descriptive classification for a Megger is a mega-ohmmeter. It is designed specifically to handle and accurately measure these high resistance values, distinguishing it from standard ohmmeters that measure lower resistance ranges.

Distinguishing Megger from Other Ohmmeter Types

• Mega-ohmmeter: This term perfectly describes the Megger's capability. It measures resistances in the mega-ohm range, which is critical for assessing the condition of electrical insulation.
• Dynamometer: A dynamometer is a device used to measure mechanical power or torque. It is not an electrical instrument for measuring resistance, and therefore, it is fundamentally different from a Megger.
• Series-type ohmmeter: This refers to a common circuit configuration for basic ohmmeters used to measure lower resistances. While a Megger is a type of ohmmeter, classifying it merely as "series-type" does not convey its specific high-resistance measurement capability. Standard series-type ohmmeters are not designed for the mega-ohm range.
• Shunt-type ohmmeter: Similar to the series-type, this describes another basic ohmmeter circuit configuration. Shunt-type ohmmeters are also typically used for measuring lower resistances and do not have the specialized high-voltage and high-resistance measurement capabilities of a Megger.

Megger's Significance in Electrical Testing

In conclusion, the Megger is fundamentally designed for measuring extremely high resistances, particularly for insulation testing. Its ability to measure values in the mega-ohm range makes it a specialized instrument beyond a general-purpose ohmmeter. Thus, it is most accurately identified as a mega-ohmmeter.