What Is Constant Temperature and Humidity Testing?
Constant temperature and humidity testing maintains a controlled temperature and relative humidity condition around a test specimen for a defined duration.
Unlike temperature cycling, which repeatedly changes the temperature, a constant temperature and humidity test normally holds the environmental conditions at a stable set point.
The test can be used to evaluate:
Moisture resistance
Corrosion susceptibility
Insulation degradation
Sealing performance
Electrical leakage
Material degradation
Connector reliability
PCB and electronic component reliability
Long-term environmental stability
Typical test conditions depend on the applicable product specification and standard. Common engineering conditions may include elevated temperature with high relative humidity for extended exposure, but the actual severity, duration, preconditioning, and acceptance criteria should always be determined from the applicable standard or product qualification specification.
Which Standards Are Used for Temperature and Humidity Testing?
Different industries use different environmental testing standards depending on the product type, application environment, and qualification requirements. The following standards are commonly referenced for temperature and humidity testing:
| Standard | Main Test Focus | Typical Application | Related Test Equipment |
|---|---|---|---|
| IEC 60068-2-78 | Damp Heat, Steady State | Electronics, electrical components, industrial equipment | Temperature & Humidity Test Chamber |
| IEC 60068-2-30 | Damp Heat, Cyclic | Automotive electronics, consumer electronics, aerospace and industrial products | Temperature & Humidity Test Chamber |
| IEC 60068 Series | General Environmental Testing | Electrical and electronic products | Environmental Test Chamber |
| ISO 16750-4:2023 | Climatic Loads | Automotive electrical and electronic components | Temperature & Humidity Test Chamber |
| MIL-STD-810H | Environmental Engineering Tests | Military, aerospace and defense equipment | Environmental / Temperature & Humidity Chamber |
| JESD22 Series | Semiconductor Reliability Testing | ICs, semiconductor devices and packages | Environmental Test Chamber / Reliability Test System |
Engineering note: The exact temperature, relative humidity, exposure duration, number of cycles, preconditioning, and acceptance criteria should be determined from the applicable standard and product-specific qualification requirements rather than from generic industry test conditions.
IEC 60068-2-78: Damp Heat, Steady State
IEC 60068-2-78 is specifically concerned with damp heat, steady-state testing.
The purpose is to determine the ability of components or equipment to withstand high humidity at a constant temperature without condensation over a specified period.
The IEC published a new edition, IEC 60068-2-78:2025, which replaces the previous edition. The 2025 edition includes revisions to test chamber requirements, severities, dew-point temperatures, temperature tolerances, preconditioning, and test reporting.
This makes IEC 60068-2-78 particularly relevant when engineers need to evaluate long-duration exposure to stable high-humidity conditions.
What Does IEC 60068-2-78 Evaluate?
Typical failure mechanisms may include:
Moisture penetration
Insulation deterioration
Electrical leakage
Corrosion
Material degradation
Seal and enclosure performance
Surface contamination effects
The test is applicable to both heat-dissipating and non-heat-dissipating specimens.
IEC 60068-2-30: Damp Heat, Cyclic
IEC 60068-2-30 evaluates resistance to cyclic damp heat.
Unlike steady-state damp heat testing, cyclic damp heat testing exposes the specimen to changing temperature and humidity conditions. These cycles can create condensation and repeated environmental stress.
This makes IEC 60068-2-30 useful when the product is expected to experience changing climatic conditions rather than a constant high-humidity environment.
Typical applications include:
Automotive electronics
Electronic assemblies
Sensors
Communication equipment
Industrial controllers
Aerospace electronics
Consumer electronics
Renewable energy equipment
For TestEQ, this standard is especially relevant to programmable temperature humidity chambers capable of automatically controlling temperature and humidity profiles.
ISO 16750-4 for Automotive Temperature and Humidity Testing
For automotive electrical and electronic components, ISO 16750-4 is an important reference.
The current published edition is ISO 16750-4:2023, titled "Road vehicles — Environmental conditions and testing for electrical and electronic equipment — Part 4: Climatic loads." It applies to electrical and electronic systems and components for road vehicles, including electric propulsion systems, and describes climatic loads and related test requirements.
Automotive engineers may use this standard when developing and qualifying:
• ECUs
• Sensors
• Connectors
• Power electronics
• Battery-related electronic systems
• On-board chargers
• Motor controllers
• Control modules
The exact test conditions should be selected according to the component's installation location, environmental exposure, and applicable product requirements.
Constant Temperature and Humidity vs Temperature Cycling
| Feature | Constant Temperature and Humidity Testing | Temperature Cycling Testing |
|---|---|---|
| Primary Purpose | Evaluate resistance to long-term temperature and moisture exposure | Evaluate reliability under repeated temperature changes |
| Temperature Condition | Maintained at a relatively constant temperature | Repeatedly changes between defined temperature levels |
| Humidity Condition | Usually controlled at a constant high relative humidity | Humidity may be controlled, varied, or not be the primary test parameter |
| Main Environmental Stress | Continuous heat and moisture exposure | Repeated thermal expansion and contraction |
| Typical Failure Mechanisms | Corrosion, moisture ingress, insulation degradation, electrical leakage, material deterioration | Solder fatigue, cracking, delamination, seal failure, mechanical stress |
| Condensation Risk | Generally minimized in steady-state damp heat testing | Depends on the temperature profile and humidity conditions |
| Test Profile | Stable temperature + stable relative humidity for a specified duration | Repeated transitions between high and low temperature |
| Typical Test Duration | Often long-duration exposure | Usually defined by the number of temperature cycles |
| Typical Standards | IEC 60068-2-78, IEC 60068-2-30, applicable ISO or product specifications | IEC 60068-2-14, ISO 16750-4, JESD22 and applicable product specifications |
| Typical Products | PCBs, connectors, sensors, electronic assemblies, automotive electronics | Semiconductor packages, PCBs, automotive electronics, connectors, assemblies |
| Recommended Chamber | Temperature Humidity Test Chamber | Temperature Cycling Chamber or Rapid Temperature Change Chamber |
| Key Selection Parameter | Temperature range, humidity range, stability, uniformity, exposure duration | Temperature range, temperature change rate, cycle profile, stability, uniformity |
| Typical Engineering Question | “Can the product withstand prolonged heat and humidity?” | “Can the product withstand repeated temperature changes?” |
Constant temperature and humidity testing focuses on sustained climatic exposure, while temperature cycling focuses on repeated thermal transitions. The appropriate test method depends on the product's intended environment, failure mechanism, and applicable qualification standard.
Constant Humidity vs Cyclic Damp Heat Testing
The key difference is whether the environmental condition remains stable or changes during the test.
Constant Humidity Testing
The specimen remains at a controlled temperature and high relative humidity for a defined period.
The main objective is to investigate long-term exposure to moisture.
Cyclic Damp Heat Testing
Temperature and humidity are programmed through repeated environmental cycles.
The changing conditions can create condensation and repeated moisture stress.
Therefore, engineers should not automatically substitute one test for the other.
The correct method depends on the applicable product specification and environmental qualification plan.
Typical Test Conditions
Temperature and humidity conditions vary significantly between standards and product specifications.
Examples of engineering test variables include:
• Test temperature
• Relative humidity
• Exposure duration
• Number of cycles
• Preconditioning
• Recovery conditions
• Specimen operating state
• Electrical monitoring
• Functional checks
• Acceptance criteria
Do not select a temperature or humidity value solely because it is commonly used in industry.
The test severity should be taken from the applicable standard, product specification, customer requirement, or qualification plan.
How Is a Constant Temperature and Humidity Test Performed?
A typical environmental qualification workflow includes:
1. Specimen Preparation
Inspect the product and record its initial condition.
Depending on the test plan, electrical or functional parameters may also be recorded.
2. Chamber Stabilization
The temperature humidity test chamber is stabilized at the required environmental condition before or during specimen installation according to the applicable test procedure.
3. Environmental Exposure
The chamber maintains the specified temperature and relative humidity for the required exposure duration.
4. Monitoring
Important parameters may include:
• Temperature
• Relative humidity
• Product temperature
• Voltage
• Current
• Functional status
• Alarm conditions
5. Recovery
After exposure, the specimen may be allowed to recover under specified environmental conditions before inspection or functional testing.
6. Evaluation
The product is evaluated against the applicable acceptance criteria.
Potential failures include corrosion, insulation degradation, electrical leakage, sealing failure, functional instability, and permanent performance changes.
What Should a Temperature Humidity Test Chamber Provide?
A chamber used for standards-based temperature and humidity testing should provide stable and repeatable environmental conditions.
Important engineering characteristics include:
Precise Temperature Control
Stable temperature control is necessary for repeatable exposure conditions.
Accurate Humidity Control
The humidity generation and measurement system should maintain the required relative humidity range without excessive fluctuation.
Good Temperature and Humidity Uniformity
The chamber should maintain consistent conditions throughout the working space so that specimen position does not create significant environmental differences.
Programmable Test Profiles
Engineers should be able to create long-duration temperature and humidity programs, including constant exposure and cyclic profiles.
Data Logging
Continuous recording of temperature and humidity helps verify the test history and supports test documentation.
Safety Protection
Long-duration environmental testing requires appropriate electrical, refrigeration, over-temperature, humidity, and system protection.
Custom Chamber Configuration
Large products, battery systems, automotive assemblies, and production equipment may require customized chamber dimensions, access doors, electrical interfaces, and monitoring systems.
Applications of Constant Temperature and Humidity Testing
Temperature and humidity testing is widely used for products exposed to moisture and climatic stress.
Automotive
Typical products include:
• ECU
• Sensors
• Connectors
• BMS components
• Power electronics
• On-board chargers
• Motor controllers
ISO 16750-4 is an important automotive reference for climatic loads.
Electronics
Temperature humidity testing can help identify:
• PCB corrosion
• Insulation deterioration
• Connector degradation
• Electrical leakage
• Moisture ingress
Semiconductor
Environmental humidity exposure may be incorporated into semiconductor reliability programs together with applicable JEDEC reliability methods.
Aerospace
Electronic systems and components may require environmental qualification for humidity and climatic exposure according to the applicable aerospace specification.
Industrial Equipment
Control systems, power supplies, sensors, communication devices, and other industrial products can be evaluated for long-term environmental stability.
Common Failure Modes Identified by Humidity Testing
Constant temperature and humidity testing can expose several environmental reliability problems.
Moisture Ingress
Moisture may penetrate through seals, interfaces, connectors, or enclosure openings.
Corrosion
High humidity can accelerate corrosion of exposed metals and conductive interfaces.
Insulation Degradation
Moisture can reduce insulation performance and contribute to leakage or dielectric problems.
Connector Failure
Humidity and contamination can increase contact resistance or promote corrosion.
PCB Failure
Moisture can contribute to corrosion, leakage currents, and long-term degradation of electronic assemblies.
Seal Failure
Environmental exposure can reveal weaknesses in gaskets, adhesives, coatings, and enclosure designs.
How to Select the Right Temperature Humidity Test Chamber
Before purchasing a chamber, engineers should define the actual test requirements.
Step 1: Identify the Standard
Determine whether the project references IEC 60068, ISO 16750, MIL-STD-810, JESD22, or another industry-specific requirement.
Step 2: Define Temperature Range
Identify the minimum and maximum test temperatures required by the qualification program.
Step 3: Define Humidity Range
Determine the required relative humidity range and whether low-humidity operation is also necessary.
Step 4: Determine Specimen Size
Select the chamber based on the specimen dimensions, fixture requirements, airflow requirements, and working volume.
Step 5: Define Test Duration
Long-duration testing places greater demands on refrigeration, humidity generation, control stability, water management, and data logging.
Step 6: Determine Whether Cycling Is Required
If the test requires changing temperature and humidity conditions, the chamber should support programmable cyclic profiles rather than only constant exposure.
Step 7: Consider Future Test Requirements
A chamber used for multiple standards may require additional control functions, monitoring interfaces, rapid temperature change capability, or customized specimen connections.
TestEQ Temperature Humidity Test Chamber
TestEQ designs and manufactures temperature humidity test chambers for environmental reliability testing across automotive, EV battery, semiconductor, aerospace, electronics, and industrial applications.
Available solutions include standard chambers, benchtop systems, floor-standing chambers, and customized walk-in environmental chambers.
Typical configurations can support:
• Temperature ranges down to approximately -70°C
• High-temperature operation up to approximately +150°C or higher depending on configuration
• Humidity control
• Programmable temperature and humidity profiles
• Long-duration environmental exposure
• Cyclic temperature and humidity testing
• Data logging and remote monitoring
• Customized chamber dimensions
• Laboratory and production testing
TestEQ's temperature humidity test chamber portfolio is designed to support environmental testing programs based on IEC 60068, ISO 16750, MIL-STD-810, JEDEC, and other applicable requirements.
For applications requiring large specimens or vehicle-level components, customized walk-in environmental chambers can also be engineered according to the required workspace and environmental conditions.
Temperature and Humidity Testing Standards: Quick Reference
| Standard | Main Test Area | Typical Test Focus | Typical Applications |
|---|---|---|---|
| IEC 60068-2-78 | Damp Heat, Steady State | Constant temperature and high humidity exposure | Electronics, components, industrial equipment |
| IEC 60068-2-30 | Damp Heat, Cyclic | Cyclic temperature and humidity exposure, including condensation effects | Automotive electronics, aerospace, industrial products |
| ISO 16750-4 | Climatic Loads | Temperature, humidity and other climatic environmental loads | Automotive electrical and electronic components |
| MIL-STD-810H Method 507 | Humidity | Humidity exposure under military environmental conditions | Military, aerospace, defense equipment |
| JESD22-A101 | Steady-State Temperature-Humidity Bias Life Test | Temperature, humidity and electrical bias stress | Semiconductor devices and packages |
| IEC 60068-2-1 | Cold | Low-temperature environmental exposure | Electronics, automotive, aerospace |
| IEC 60068-2-2 | Dry Heat | High-temperature environmental exposure | Electronics, industrial equipment, automotive |
| IEC 60068-2-14 | Temperature Change | Controlled temperature transitions | Electronics, automotive, aerospace |
| IEC 60068-2-38 | Composite Temperature/Humidity Cyclic Test | Combined temperature and humidity cycling | Electronic components and assemblies |
Note: The applicable test method, temperature, relative humidity, exposure duration, cycle profile, and acceptance criteria should always be determined according to the latest applicable standard and the product-specific qualification requirements.
Why Choose TestEQ for Temperature & Humidity Testing?
Choosing the right temperature humidity test chamber is important for achieving stable, repeatable, and standards-based environmental testing. TestEQ combines environmental chamber manufacturing with application-focused engineering support for laboratory and industrial testing.
Engineering-Focused Chamber Design
TestEQ designs temperature humidity test chambers around actual test requirements, including temperature range, humidity range, working volume, test profile, uniformity, stability, and specimen configuration.
Support for International Testing Standards
TestEQ chambers can be configured for environmental testing programs based on standards such as IEC 60068, ISO 16750, MIL-STD-810, and JEDEC, depending on the required test method and application.
Standard and Custom Solutions
From benchtop and floor-standing chambers to large-capacity and customized environmental test systems, TestEQ can provide configurations for electronics, automotive, EV battery, semiconductor, aerospace, and research applications.
Technical Support from Selection to Testing
TestEQ can assist engineering and procurement teams with chamber selection, test-condition evaluation, chamber configuration, and application requirements, helping ensure that the selected system matches the intended qualification program.
Need help selecting a temperature humidity test chamber? Contact TestEQ for a technical recommendation or customized quotation.
Frequently Asked Questions
1.What is the main standard for constant temperature and humidity testing?
IEC 60068-2-78 is one of the most directly relevant standards because it covers damp heat, steady-state testing at high humidity and constant temperature without condensation. The current IEC edition is IEC 60068-2-78:2025.
2.What is the difference between IEC 60068-2-78 and IEC 60068-2-30?
IEC 60068-2-78 focuses on damp heat, steady state, while IEC 60068-2-30 focuses on cyclic damp heat. The latter introduces changing temperature and humidity conditions and can produce condensation-related environmental stress.
3.Is ISO 16750 used for temperature and humidity testing?
Yes. ISO 16750-4:2023 addresses climatic loads for electrical and electronic systems and components used in road vehicles.
4.What chamber is used for constant temperature and humidity testing?
A programmable temperature humidity test chamber is normally used. The chamber should provide appropriate temperature and humidity control, uniformity, monitoring, and programmable test profiles.
5.What products require temperature humidity testing?
Automotive electronics, sensors, connectors, PCBs, semiconductor devices, communication equipment, industrial controllers, aerospace electronics, battery-related components, and other products exposed to climatic environments may require this type of testing.
6.Does humidity testing always require temperature cycling?
No. Constant damp heat and cyclic damp heat are different test approaches. The applicable standard and product qualification plan determine whether the environmental condition should remain constant or change during the test.
7.How long does a constant temperature humidity test take?
The duration depends on the applicable standard, product specification, test severity, and qualification objective. Engineers should not assume a universal test duration.
8.Can TestEQ customize a temperature humidity test chamber?
Yes. TestEQ can engineer chamber capacity, temperature range, humidity range, access configuration, monitoring interfaces, and other system requirements for laboratory, production, automotive, EV battery, semiconductor, aerospace, and research applications.
Internal Linking Module
Recommended Equipment
Designed for constant temperature and humidity testing, this chamber provides controlled temperature and relative humidity conditions for IEC 60068, automotive, electronics, semiconductor, and reliability testing applications.
A versatile solution for temperature, humidity, and environmental reliability testing. It is suitable for laboratories and manufacturers that need programmable environmental conditions across multiple test standards.
Designed for large components, battery systems, vehicle parts, and production-scale testing. Walk-in configurations provide a large working space for temperature and humidity qualification of oversized specimens.
Related Standards
Explore the IEC 60068 environmental testing series, including temperature, humidity, thermal cycling, vibration, and other environmental test methods used for electrical and electronic product reliability.
Learn how IEC 60068-2-30 evaluates product resistance to cyclic damp heat and changing temperature and humidity conditions, including applications and chamber requirements.
Understand combined temperature and humidity testing under IEC 60068-2-38 and how environmental chambers are configured for reliability evaluation of electronic and industrial products.
Technical Resources
Understand the major standards used for temperature and humidity testing, including IEC 60068 and automotive environmental testing requirements, with practical guidance for engineers selecting test equipment.
Learn how to select an environmental test chamber based on temperature range, humidity control, chamber volume, test profile, uniformity, and applicable reliability testing standards.
Learn how chamber temperature, humidity, uniformity, stability, and measurement performance can be validated and calibrated to support repeatable environmental testing.
CTA
Need a Temperature Humidity Test Chamber for Standards-Based Testing?
If you are planning IEC 60068, ISO 16750, MIL-STD-810, JEDEC, or another environmental qualification program, the chamber should be selected according to the actual test method rather than temperature range alone.
TestEQ can help engineers and procurement teams evaluate:
• Required temperature and humidity range
• Chamber working volume
• Test profile and cycle requirements
• Temperature and humidity uniformity
• Long-duration stability
• Data logging requirements
• Custom chamber configuration
• Laboratory or production integration
"Request a Temperature Humidity Test Chamber Solution from TestEQ"
