# Insulation resistance meter

Canonical URL: https://eloragrid.ai/symbols/insulation-resistance-meter
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: MΩ
Drawing use: Schematic
Reference families: IEC, Manufacturer

Indicating instrument applying a high DC test voltage to read insulation resistance in megohms.

## In plain English

### What does Insulation resistance meter mean?

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.

### A simple example

The test voltage can damage electronics and leaves charge on capacitive cables, so the drawing should show what must be disconnected and how the circuit is discharged afterwards. The symbol itself does not state the test voltage or the acceptance value.

### What the drawings help you do

Identify electronics that must be disconnected before testing. Check the test voltage suits the insulation rating. An insulation resistance meter is a periodic test instrument; an insulation monitoring relay checks an unearthed system continuously in service.

### This particular reference

Indicating instrument applying a high DC test voltage to read insulation resistance in megohms. An insulation resistance meter is a periodic test instrument; an insulation monitoring relay checks an unearthed system continuously in service.

### Terms

- DC: Direct current: electricity flowing in one direction.
- Rating: A value stating the conditions for which equipment is specified.
- Schematic: A drawing showing function and connections rather than physical appearance.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/)


## What it represents

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.
The test voltage can damage electronics and leaves charge on capacitive cables, so the drawing should show what must be disconnected and how the circuit is discharged afterwards. The symbol itself does not state the test voltage or the acceptance value.

## How to read it

- Identify electronics that must be disconnected before testing.
- Check the test voltage suits the insulation rating.

## Information to show or reference

- State test voltage
- Show disconnection points
- Reference discharge procedure

## Important distinction

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

## Facts

- Measured quantity: Insulation resistance in megohms
- Test source: High-voltage DC from the instrument
- Preview: Independent educational concept; consult the applicable standard and project legend for the exact graphic

## Public references

- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/) — IEC. IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.