Megaohm

A megaohm (symbol MΩ) is a unit of electrical resistance equal to 1,000,000 ohms. The name combines the prefix mega- (10^6) with the ohm (Ω). In SI units, 1 MΩ equals 1,000,000 Ω and is equal to 1,000 kiloohms (kΩ).

Usage: The megaohm is used to express very high resistances commonly encountered in insulation and leakage paths, such as electrical cables, insulators, and high-voltage equipment. Insulation resistance testers, often called megohm meters, apply a DC voltage and measure resistance, reporting values in MΩ.

Practical considerations: Measurements at the megohm scale are sensitive to moisture, temperature, contamination, and measurement setup, so readings may vary with conditions. The symbol MΩ is preferred to avoid confusion with the milliohm symbol mΩ, since M (mega) and m (milli) differ by a factor of one million.

See also: Ohm; Insulation resistance; Electrical resistance.