What Is Humidity?
This test is carried out to evaluate the equipment in high relative humidity conditions within the scope of Chapter 6 (“Humidity”) of the RTCA DO-160 “Environmental Conditions and Test Procedures for Airborne Equipment” standard. DO-160 is the exact same text as EUROCAE ED-14 and is recognized by ISO as ISO 7137.
Purpose of Humidity
The aim is to certify that aviation equipment meets the requirements for evaluation of equipment in high relative humidity conditions in flight and ground conditions and to complete equipment qualification.
Which Products Is Humidity Applied To?
- Avionics units and displays
- In-flight electronic equipment
- Communication and navigation devices
- Cabin and cargo compartment equipment
- Sensors and actuators
In Which Sectors Is Humidity Used?
Standards Related to Humidity
- RTCA DO-160Environmental conditions and test methods in aviation equipment test
- EUROCAE ED-14
- ISO 7137
- EN 50155electronic equipment in railway vehicles test
- EN 50121electromagnetic compatibility in railway applications test
- EN 45545fire safety in railway vehicles test
- IEC 61373vibration and shock in railway vehicle equipment test
Humidity Conditions
- Kategoriler
- A (standard humidity), B (severe humidity), C
- Cycle
- Temperature and humidity cycles; number of days by category
- Relative humidity
- High humidity levels defined in the standard
- Function check
- At the end of the cycle and, if necessary, in the cycle
Equipment for Humidity
- Temperature-humidity chamber
- Insulation resistance measuring instrument
- Function monitoring
Sample Requirements for Humidity
- Category must be defined
- Initial insulation resistance should be measured
- Condensation management should be planned
Duration of Humidity
It depends on the category; The severe humidity category may exceed ten days.
Humidity Procedure
- 1The category and cycle program are determined.
- 2The specimen is placed in the chamber.
- 3Temperature-humidity cycles are applied.
- 4At the end of the cycle, function and insulation are measured.
- 5A visual inspection is performed.
Humidity Acceptance Criteria
The acceptance criteria are that the function continues, the insulation resistance meets the limit and there is no corrosion.
Evaluation of Results
Moisture ingress usually occurs at connector and housing junctions.
Humidity Report
- Applied standard, revision and Chapter 6
- Selected equipment category and justification
- Applied conditions and measurement results
- Function monitoring method and observations
- Environmental Qualification Form (DO-160 Environmental Qualification Form) entry
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 authorisationsRelated Regulations
- Aviation equipment qualification requirements
- EASA/FAA certification principles
Demiryolu Testleri — What Does This Testing Field Cover?
The section below describes the field that the 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.
Railway testing shows that vehicles and components operate safely and reliably in the rail environment. The character of this family comes from the ASSUMPTION OF LONG LIFE: a rail vehicle is designed for a service life exceeding thirty years and its components remain under vibration, temperature cycling and intensive use throughout that period.
Long life also shapes the component supply chain. Spare parts must remain available for thirty years, electronic components going out of production must be replaced, and every substitution must be re-verified. This takes railways out of a "certify once and carry on" logic.
Fire safety is the most tightly regulated part of the field and runs through the EN 45545 series. The logic of the series rests on the LOCATION OF USE and the OPERATION CATEGORY: a metro running in tunnels and an intercity train do not carry the same risk, and seat fabric and cable are not assessed in the same category. Evacuation time is the main factor setting these categories; because evacuation takes longer in an enclosed tunnel, the material requirements become stricter.
For electronic equipment, EN 50155 is the framework standard and carries environmental, electrical and functional requirements together: supply voltage variations, temperature classes, humidity, vibration and shock. On the vibration and shock side the EN 61373 categories are used and these differ by mounting location — a box mounted on the body and a sensor mounted on the bogie do not go through the same profile.
On electromagnetic compatibility the EN 50121 series applies and addresses a problem peculiar to railways: the traction system switches at very high power and can affect both the systems on board and the signalling along the line. The series therefore carries separate parts for the vehicle, lineside installations and signalling.
For safety-related systems a separate body of work applies, and here the evidence is not testing but PROCESS: EN 50126 (RAMS), EN 50128 (software) and EN 50129 (safety-related electronic systems) define the safety life cycle and the safety integrity levels (SIL). Signalling and brake control systems are assessed within this framework.
On the quality side, the sector's own scheme IRIS (ISO/TS 22163) comes into play; major vehicle manufacturers require this certificate from their suppliers.
On the mechanical structure side, the car body and bogie frame have standards of their own: structural verification under static and fatigue loads, weld quality and crashworthiness. These tests are carried out on full-scale rigs and can take months.
Method groups in this field
Fire safety
Classification of materials and components under EN 45545; the requirement set according to operation and design category.
Electronic equipment
EN 50155 environmental and electrical requirements; supply interruptions, temperature classes, humidity and degree of protection.
Vibration and shock
EN 61373 categories; body, bogie and axle-mounted profiles according to mounting location.
Electromagnetic compatibility
The EN 50121 series: separate parts for the vehicle, lineside installations and signalling.
Safety life cycle
EN 50126 RAMS, EN 50128 software and EN 50129 safety-related systems; SIL determination and the safety case.
Structural verification
Static and fatigue loads on the car body and bogie frame, weld quality, crashworthiness.
Commonly confused in this field
- EN 45545 requirements vary with the location of use and the operation category; there is no single "railway fire class".
- Conformity to EN 50155 does not cover the vibration requirements; EN 61373 is applied in addition.
- A civil EMC report is not sufficient for railways; the EN 50121 series defines a different environment and different limits.
- For safety-related systems, testing alone is not evidence; safety life cycle records are required.
- A component change (even one driven by obsolescence) requires re-verification; in long-life projects this is routine work.
- An IRIS certificate is not a product approval; it is a quality system certificate.
Which decisions these results support
- Vehicle and component approval, operator acceptance processes
- Material selection according to the fire safety category
- The safety case and SIL evidence for safety-related systems
- Supply chain quality certification
- Continuity of component supply and change management
Related Tests
Frequently Asked Questions About Humidity
How is the equipment category determined?
The category is selected based on the equipment's mounting location on the aircraft (pressurized/non-pressurized, heated/unheated area) and aircraft type. Category selection directly determines the test conditions and is declared in the qualification form.
Is there any difference between DO-160 and ED-14?
No. RTCA DO-160 and EUROCAE ED-14 are exactly the same text; the two are considered equivalent.