Insulation Resistance Test — ISO 6469-3 / UNECE R100

What Is Insulation?

The insulation resistance test measures the resistance between the high-voltage circuit and the vehicle chassis (electrical chassis) in electric vehicles. This resistance is the basic protection against the risk of touching high voltage, and is a safety parameter that must be monitored throughout the vehicle's lifetime.

Purpose of Insulation

The purpose is to verify that the high-voltage system is adequately insulated from the chassis, and to produce the evidence required for type approval.

Which Products Is Insulation Applied To?

Electric and hybrid vehicles
Battery packs
Inverters and DC/DC converters
High-voltage wiring harnesses
Charging systems

In Which Sectors Is Insulation Used?

AutomotiveElectrical & Electronics

Standards Related to Insulation

ISO 6469-3
UNECE R100electric vehicle and battery safety test
IEC 60664-1
ISO 6469-1

Insulation Conditions

Measurement voltage: DC is applied at the value prescribed by the standard, according to the system's operating voltage
Measurement points: Separately between the positive and negative poles and the electrical chassis
Environment: Since the measurement is affected by humidity, ambient conditions are recorded

Equipment for Insulation

High-voltage insulation-resistance meter (megohmmeter)
Safety barriers and personal protective equipment
Climatic chamber (for assessing the effect of humidity)
Data logger

Sample Requirements for Insulation

Complete vehicle or high-voltage component
The system must be de-energised and made safe before the measurement
System voltage and topology information must be provided
Access to the measurement points must be planned

Duration of Insulation

The measurement itself is short; if measurement after humidity conditioning or an environmental test is required, the duration extends accordingly.

Insulation Procedure

1The system is de-energised and safety measures are taken.
2Measurement points are determined and access is provided.
3The measurement voltage prescribed by the standard is applied.
4The resistance between the positive pole and the chassis is measured.
5The resistance between the negative pole and the chassis is measured.
6Ambient temperature and relative humidity are recorded.
7The measurement is repeated after environmental tests, if required.

Insulation Acceptance Criteria

Under UNECE R100 and ISO 6469-3, insulation resistance must be above a minimum value (in Ω/V) referenced to the system's operating voltage. The applicable value is taken from the standard's text, according to whether the system is DC or AC and its topology.

Evaluation of Results

The measured resistance is compared with the minimum value required by the system voltage. Since humidity and contamination markedly lower the values, measurements after environmental tests show the design's real robustness.

Insulation Report

Standard applied
System description and operating voltage
Measurement voltage and points
Ambient temperature and humidity
Measured resistance values
Comparison with the minimum requirement

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

UNECE R100
ISO 6469-3

Otomotiv Testleri — What Does This Testing Field Cover?

The section below describes the field that the Insulation test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Automotive testing shows that a component keeps working under conditions representing the loads it will meet over the life of the vehicle. A vehicle is not a single product but an ENVIRONMENT: vibration, temperature cycling, salt water, stone impact, electrical transients and electromagnetic noise are all present at the same time and for years.

What distinguishes this family is that VEHICLE MANUFACTURER SPECIFICATIONS sit on top of the standards. ISO and SAE publications establish the common ground; but Volkswagen, BMW, Ford, Stellantis, Toyota and Renault define different severity levels, additional tests and different acceptance criteria in their own specifications. For a component, the phrase "complies with automotive standards" is not sufficient on its own; which manufacturer's specification, and which revision of it, must be answered.

The family carries three separate processes together and they are often confused. Homologation covers the type approvals a vehicle needs to enter traffic and runs under state authority. Supplier approval means passing the vehicle manufacturer's own quality and testing requirements and is a commercial relationship. The third is design verification: the engineering team demonstrating that its own design meets its targets.

At component level the test plan is built around the LOCATION OF USE. A module in the engine bay and a module in the boot do not go through the same temperature and vibration profile; a component inside a door and one in the roof console do not see the same water and dust exposure. The ISO 16750 series is the common framework for this location-based approach.

The shift to electric vehicles has reshaped the field. High-voltage safety, insulation coordination, battery safety, charging interface conformity and the electromagnetic behaviour of high-voltage components have been added to the classical automotive test set. In a quiet vehicle, acoustic and vibration expectations have changed too; sounds once masked by the combustion engine are now audible.

The quality system side cannot be separated from testing in this field. A manufacturer under IATF 16949 presents test results in the PPAP file; measurement system analysis, process capability study and the control plan stand around the test report. A single good result is not enough — the process must be shown to be able to repeat it.

Method groups in this field

Environmental and climatic
Temperature cycling, thermal shock, damp heat, salt spray, dust and water ingress (IP), solar radiation. Severity levels vary with the mounting location.
Mechanical
Sine and random vibration, shock, mechanical loads, fastener torque and durability cycles.
Electrical
Supply voltage variations, transients (ISO 7637), reverse polarity, overvoltage, short circuit and sleep current measurements.
EMC
Component emissions (CISPR 25), radiated and conducted immunity (ISO 11452 series), electrostatic discharge (ISO 10605).
Materials and emissions
Odour, fogging and VOC emissions from interior materials; flammability; UV ageing; coating durability and stone impact.
Functional safety and cyber security
Functional safety evidence under ISO 26262 and cyber security engineering under ISO/SAE 21434; these are tied to regulation through UNECE R155 and R156.

Commonly confused in this field

An automotive report without a specification reference is not accepted in the supply chain; which OEM specification and revision was applied must be stated.
Type approval and supplier approval are different processes. A component with E-Mark approval is not thereby considered to have passed the OEM's own acceptance tests.
A result obtained on a prototype does not carry over to series production; PPAP is done with series production parts.
On the EMC side, measuring emissions alone is incomplete; immunity is a separate body of work and is more critical in a vehicle.
On electric vehicle components, high-voltage safety is a distinct competence; classical 12 V test infrastructure is not sufficient.

Which decisions these results support

Supplier component approval and the PPAP file
UNECE type approval and E-Mark marking
Design verification and durability evidence
Root cause analysis of field complaints and warranty returns
Assessing the impact of a design or supplier change

Related Tests

Frequently Asked Questions About Insulation

The vehicle monitors its own insulation — is testing also required?

Yes. The on-vehicle insulation-monitoring system provides protection during operation, while type approval requires verification by an independent measurement. That the monitoring system itself operates correctly is also verified separately.

Why does humidity affect the result?

Moisture and contamination on the surface form a conductive path across insulating surfaces and lower the measured resistance. Ambient conditions are therefore recorded in the report, and critical assessments are performed under conditioned conditions.