Sabit Nem – IEC 60068-2-78

What Is Steady Humidity — IEC 60068-2-78?

The steady-state humidity test is an environmental test in which the sample is held for an extended period at a constant temperature and constant high relative humidity. It is defined as method Cab in IEC 60068-2-78.

Purpose of Steady Humidity — IEC 60068-2-78

The purpose is to assess the long-term effect of humidity on insulation resistance, corrosion and material degradation.

Which Products Is Steady Humidity — IEC 60068-2-78 Applied To?

Electronic boards and modules
Insulation materials
Coated metal parts
Connector and cable connections
Lighting fixtures

In Which Sectors Is Steady Humidity — IEC 60068-2-78 Used?

ElectronicsElectricalAutomotiveDefenceAerospace

Standards Related to Steady Humidity — IEC 60068-2-78

IEC 60068-2-78constant moist heat test test

Steady Humidity — IEC 60068-2-78 Conditions

Temperature: Defined in the specification; typical values 30, 40 or 85 °C
Relative humidity: Typically 85% or 93%
Time: Defined in the specification; typically 96, 240, 500 or 1000 hours
Operating condition: Working or off; voltage is applied in some specifications

Equipment for Steady Humidity — IEC 60068-2-78

Temperature and humidity chamber
Humidity sensor and calibration setup
Insulation resistance measuring instrument
Function-monitoring rig

Sample Requirements for Steady Humidity — IEC 60068-2-78

The sample must be placed so that no dripping occurs in the chamber
Insulation resistance and function must be measured before the test
If condensation on the sample surface is not desired, conditions must be set accordingly
The number of specimens is set out in the specification

Duration of Steady Humidity — IEC 60068-2-78

Depends on the duration defined in the specification; typically four days to six weeks.

Steady Humidity — IEC 60068-2-78 Procedure

1Initial insulation resistance and function are measured.
2The specimen is placed in the chamber.
3Temperature and humidity are brought to their target values.
4The conditions are maintained for the defined duration.
5The sample is removed; measurements are taken within the time defined in the standard.
6Corrosion and degradation are assessed by visual inspection.

Steady Humidity — IEC 60068-2-78 Acceptance Criteria

The acceptance criterion is defined in the product standard: insulation resistance not falling below the limit, continuity of function, and no corrosion.

Evaluation of Results

How soon after removal the measurements are taken affects the result; the standard limits this time and it is stated in the report.

Steady Humidity — IEC 60068-2-78 Report

Standard and method applied
Temperature, relative humidity and duration
Measurement timing
Insulation resistance and function results
Visual inspection

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

LVD 2014/35/EU
Electronic component specifications

Environmental and Climatic Testing — What Does This Testing Field Cover?

The section below describes the field that the Steady Humidity 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.

Environmental testing shows whether a product withstands ambient factors such as temperature, humidity, pressure, solar radiation, dust, water and corrosive atmospheres. The aim is not to break the product but to bring forward, in ACCELERATED form, the conditions it will meet over its life.

Test profiles are derived from the product's real exposure, and that derivation is the actual engineering work of the field. A device operating in an enclosed office and one mounted on a pole are not tested with the same profile. The IEC 60068 series defines general methods, MIL-STD-810 military profiles, RTCA DO-160 aviation profiles and the ISO 16750 series location-based automotive profiles. A test applied without a profile selection produces both unnecessary cost and false confidence.

Temperature tests simulate three separate phenomena and all three produce different failure modes. Steady high/low temperature tests whether the material can operate at that temperature. Temperature CYCLING creates fatigue at joints between materials with different expansion coefficients — solder cracks appear here. Thermal SHOCK intensifies this effect through an abrupt transition.

There is a distinction in humidity testing too. Steady damp heat shows the diffusion of moisture into the material and its effect on insulation properties. Cyclic damp heat creates condensation: water droplets form on the cooling surface, and this is far more aggressive than dry humidity. Water ingress into enclosures, increased leakage current and corrosion usually appear in the cyclic test.

Dust and water protection is a separate body of work and is expressed by the IP code. The point to note here is that an IP test is not a DURABILITY test: it shows that protection is provided under defined and short-duration conditions, not resistance to long-term immersion or pressure washing.

The most common mistake in this family is translating a test result directly into a LIFE PREDICTION. Accelerated tests are designed for comparison and design verification; a reliable conversion between hours in a chamber and years in the field can only be established with a material-specific acceleration model calibrated against field data.

Functional monitoring determines the value of the test. Keeping a product in a temperature chamber and then switching it on does not show what happened DURING the test. In critical applications the product is operated throughout the test and its parameters are monitored; intermittent faults that appear and disappear can only be caught this way.

Method groups in this field

Temperature
Dry heat, cold, change of temperature and thermal shock; steady and cyclic profiles.
Humidity
Steady damp heat and cyclic damp heat; cycles with condensation are more aggressive.
Water and dust
IP protection tests: dripping, spraying, jets, immersion and dust tightness.
Radiation and ageing
Accelerated ageing by xenon arc and fluorescent UV, solar radiation simulation.
Pressure and altitude
Low pressure (altitude) and rapid pressure change tests.
Corrosive atmosphere
Salt spray, mixed flowing gas corrosion (simulating industrial atmospheres), mould and fungus tests.

Commonly confused in this field

Test duration cannot be converted into field life; a conversion made without an acceleration model is misleading.
Temperature cycling and steady temperature produce different failure modes; neither replaces the other.
If the product is not operated during the test, intermittent faults remain invisible; functional monitoring determines the value of the test.
IP protection is not evidence of durability; it shows protection under defined and short-duration conditions.
A test applied without profile selection both increases cost and gives false confidence.
The mounting and orientation arrangement affects the result; the report must document it.

Which decisions these results support

Design verification and qualification
Declaration of the protection class and operating temperature range
Reproducing field failures in the laboratory and root cause analysis
Supplier component approval
Decisions on warranty period and storage conditions

Related Tests

Frequently Asked Questions About Steady Humidity — IEC 60068-2-78

According to which standard is Steady Humidity made?

Steady Humidity is executed in scope IEC 60068-2-78, IEC 60068-2-56, ISO 16750-4 and MIL-STD-810 Method 507. The limit values and acceptance criteria to be applied are defined in the product standard; The version valid for your product is confirmed in writing at the offer stage.

Which products does Steady Humidity apply to?

Mainly applied to Electronic boards and modules, Insulation materials, Coated metal parts, Connector and cable connections and Lighting fixtures. Whether your product is included in the scope is determined by examining its technical specifications and intended use.

Under what conditions is Steady Humidity done?

The determining parameters are: Temperature — Defined in the specification; typical values 30, 40 or 85 °C, Relative humidity — Typically 85% or 93% and Time — Defined in the specification; typically 96, 240, 500 or 1000 hours. The full terms are in the "Test Conditions" section on the page and vary depending on the product standard.

What kind of sample is needed for Steady Humidity?

The sample must be placed so that no dripping occurs in the chamber, Insulation resistance and function must be measured before the test and If condensation on the sample surface is not desired, conditions must be set accordingly. The number of samples is determined according to the product standard and the scope to be reported.

How long does Steady Humidity take?

Depends on the duration defined in the specification; typically four days to six weeks. This duration belongs to the experiment itself; sample preparation, queuing and reporting are also evaluated. A realistic schedule for your product is given in the offer.

What is the Steady Humidity result called "appropriate"?

The acceptance criterion is defined in the product standard: insulation resistance not falling below the limit, continuity of function, and no corrosion.