Side-by-side reference

Understand the difference.

Compare the meaning, drawing context and source references of two entries. A similar graphic or shared abbreviation does not establish equivalence.

First referenceCompare with

MΩ

Symbols

Insulation resistance meter

An insulation resistance meter applies a DC test voltage, typically hundreds or thousands of volts, between conductors and earth and reads the leakage as resistance in megohms. On drawings it appears in test procedures and in permanently installed test panels for motors and cables.

Drawing use: Schematic
Application: Metering & protection
Reference family: IEC / Manufacturer

A distinction that matters

An insulation resistance meter is a periodic test instrument; an insulation monitoring relay checks an unearthed system continuously in service.

Full reference

Symbols

Ohmmeter

An ohmmeter indicates resistance by passing a small current from its own source and measuring the result. On permanent drawings it appears in test equipment, earthing test points and some machine monitoring panels, while on schematics for test procedures it shows where resistance is to be measured.

Drawing use: Schematic
Application: Metering & protection
Reference family: IEC / IEEE / ANSI

A distinction that matters

An ohmmeter measures ordinary resistance at low voltage; an insulation resistance meter applies a high test voltage to measure megohms.

Full reference

Original educational previews. Follow the source references on each full entry for the appropriate standard or selected product.