Ω
Ohmmeter
Indicating instrument for electrical resistance, shown as an instrument circle marked with the ohm sign.
Schematic
Symbols · MΩ
Insulation resistance meter
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.
- 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.
Read the source: IEC graphical symbols for diagrams
Schematic · MΩ
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
A distinction that matters
An insulation resistance meter is a periodic test instrument; an insulation monitoring relay checks an unearthed system continuously in service.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
IEC graphical symbols for diagrams
IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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