Designing embedded hardware to withstand rugged environments

28th September 2012

When fighting a warehouse fire in extraordinary temperatures, you don’t want to worry about the two-way radio breaking down. If a police car is broadsided during a high-speed chase, the on-board computer can’t be torn free to become a dangerous projectile. When staking out a remote location in the desert or on or drilling for oil in the North Sea, electronic equipment needs to withstand the extreme weather.

When designing projects for extreme environments such as the previous examples, you need rugged electronic designs. To make sure your clients and end users in the field have technology they can rely on, a number of organisations have developed stringent industry testing standards and procedures. This has an impact on product design as engineers are required to know, design and test their equipment to comply with set standards. The desired end here is for the products to survive “Torture Tests” and gain compliance certificates.

Ruggedisation is defined as “designed or improved to be hard-wearing or shock-resistant. There are four categories of rugged electronic equipment; commercial-grade; durable; semi-rugged and fully rugged. Today’s most widely used ruggedness standards include those from four highly respected sources: the International Electrotechnical Commission (IEC), the European Committee for Electrotechnical Standardisation (CENELEC) which publishes the European IP (Ingress Protection) standards for electrical equipment, and the United States military.

Most standards provide exceptionally detailed instructions and procedures for product testing. Major tests normally performed include:

  • Water Intrusion: When water or rain penetrates a device, they can cause short circuits and corrosion. Many manufacturers test their rugged products against both MIL-STD-810F and IP54, IP64, IP66 water and rain intrusion standards. Testing for rain intrusion is normally done in a rain chamber that drenches products with jets of water of varying intensities from all possible angles, as well as for dripping water for different periods of time. Fully rugged models are also tested with full immersion, to IP68 and MIL-STD-810F, Method 512.4.
  • Salt and Fog: In coastal and marine environments, salt and fog can cause electronic equipment to short circuit or rust, affecting performance both short and long-term. Engineers normally test to the MIL-STD-810F Method 509.3 standard using the specified five percent saline solutions.
  • Humidity: Conditions of extreme humidity can cause electronic devices to corrode and malfunction over time. Typical tests are to MIL-STD-810F Method 507.3 specifications, which specify 95 percent relative humidity and worst-case scenario high temperatures up to 75°C.
  • Dust Intrusion: Dust and sand intrusion in deserts, shorelines, mines, construction sites, or other environments can cause movable parts like buttons and keypads to clog and malfunction. Often manufacturers test to both MIL-STD-810F, Method 510.3 for sand and dust testing and IP standards for blowing dust.
  • Drop Testing: In the field, it’s common for handheld devices to be knocked over or dropped. Manufacturers test to MIL-STD-810F Method 516.5 with around 90- to 120 cm free-fall drops to concrete, and also with tip-over tests. The equipment is expected to remain fully operational after multiple drops.
  • High and Low Temperatures: Manufacturers test their technology under operating conditions of minus 35°C (MIL-STD-810F Method 502.3) and plus 60°C (MIL-STD-810F 501.3). In addition, equipment is often stored under extreme temperature conditions, and is expected to work to specification when put into service. Many manufacturers tests equipment storage in extreme low temperatures down to minus 57°C (also MIL-STD-810F Method 502.3) and high temperatures up to 85°C (also MIL-STD-810F 501.3).
  • Temperature Shock: Equipment is often transported by aeroplane, or used outdoors and brought inside, meaning it can be under extreme cold for long periods of time, then deposited or stored in extreme heat. Equipment is tested under these precipitous temperature fluctuations to MILSTD- 810F Method 503, testing equipment that has gone from storage of minus 57°C to 80°C and vice versa.
  • Sun Exposure: Equipment that is installed in, or must work in, unrelenting sunshine is tested to MIL-STD-810F Method 505.4 standards for enclosure and performance damage from solar radiation. Tests normally last from three to seven days, and are conducted in a specially designed solar chamber.
  • Shock and Crash Testing: Mobile and vehicle mounted products are tested to make sure they are installed correctly by subjecting them to worst-case scenario accident impact tests. MILSTD- 810F Method 516.4 tests are exceptionally stringent. Equipment must continue to operate correctly under 75Gs, or 75 times the force of gravity. Drop tests of varying heights to a steel floor are also conducted. Equipment must stay intact, mounted and continue to be 100 percent functional.
  • Vibration: Vibration testing to MIL-STD-810F Method 514.5 measures how equipment reacts to different levels of vibration, which can cause wire chafing, intermittent electrical contacts, display misalignment and other issues. Tests are conducted in both standard vehicles such as cars and trucks and under the more severe vibrations caused by more vibration-prone vehicles such as motorcycles, tanks and others.
  • Low Pressure: High altitudes and dropping pressure, such as in aircraft or on mountains, can cause membranes in parts such as speakers, microphones and keypads, to malfunction. Manufacturers conduct low-pressure performance tests to MIL-STD-810F Method 500.3 that ensure 100 percent equipment functionality

To ensure that products go to market quickly and don’t suffer costly delays, engineers should include relevant testing consideration as part of the design process. By confirming assumptions of the product’s compliance—such as the market and classification of the area in which the equipment will be used (Class I, Division 1, Class I, Zone 0 etc.), determining the appropriate protection concept (intrinsic safety, flame-proof, etc.), and establishing the indicative environmental considerations (enclosure ratings, extended ambient temperature range and so on) product development will be smoother and not require reworking to meet aforementioned standards.

The recommendation is for engineers proceeding into research and development stages to keep the submission for final certification in mind. This could mean reaching out to consultants who will help you through your submission process and follow their advice and guidelines.

At the LX Group we can carry out product testing, verification and compliance certification. We also partner with a number of NATA-certified local and international partners to provide independent product compliance and environmental testing.

LX has a range of equipment to support environmental and certification testing including an environmental test chamber, EMC test equipment, ESD simulator (CE testing), and various electrical input simulation devices such as environmental testing, design verification and compliance testing.

Some common compliance standards include:

  • EMC emissions and immunity testing (including C- Tick, FCC and CE)
  • Electrical safety (mains certification)
  • UL certification
  • RoHS and WEEE compliance
  • Industry-specific standards (including medical and mining)
  • Ingress Protection (IP) rating
  • Packaging and labelling requirements

For more information or a confidential discussion about your ideas and how we can help bring them to life – click here contact us, or telephone 1800 810 124.

LX is an award-winning electronics design company based in Sydney, Australia. LX services include full turnkey design, electronics, hardware, software and firmware design. LX specialises in embedded systems and wireless technologies design.

Published by LX Pty Ltd for itself and the LX Group of companies, including LX Design House, LX Solutions and LX Consulting, LX Innovations.

Muhammad AwaisDesigning embedded hardware to withstand rugged environments

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