Backgrounder: sensing in harsh industrial environments
The use of sophisticated electronic and sensing devices to improve and expand manufacturing, machining, and production processes in industrial applications is only possible if all components survive the environment. Some systems must endure hot, humid, and harsh conditions and destructive electric and magnetic fields. This report from Farnell explains the basics
The specific environmental conditions in which a product is used affects its specifications. Such specifications must be determined at the beginning. Difficult conditions in industrial applications include particulate ingress, extreme temperature, physical impact, Electrostatic Discharge (ESD), Electromagnetic Interference (EMI), and vibration. All these conditions, if unchecked, will destroy electronic equipment over time.
High temperatures are a major contributor to a punishing environment. A cool climate is a necessity for effective electronic device operational performance. The microclimate inside the automobile hood is a toxic one where the ambient temperature rarely drops below 125°C. Combustion and exhaust gas sensors must work in heated, harsh environments. High-temperature electronics must make up the control circuitry administering the actuators and sensors.
When used in high-temperature environments, electronics must have active or passive cooling to keep parts within their respective operating temperature ranges. This is impractical in most real-world situations. Semiconductor (IC) robustness includes operating temperature range, fault protection, managing high electrical noise, and ESD. Robustness is a crucial performance factor for an extended operation and obtains a reputable, reliable final product. Durability is a must in an industrial ecosystem characterized by extreme operating conditions, with IC temperatures swinging anywhere between -40 to +85°C. Elevated temperature operation is here to stay, and the automotive industry may eventually witness working temperatures between -40 to +125°C.
Thermal issues crop up when electronic devices are kept in an air-tight industrial indoor environment. The devices dissipate heat, and rising temperatures will damage devices if improperly managed. Voltage regulators and power ICs use thermal shutdowns to prevent such a scenario. Choosing packages with super low thermal impedances help to transfer heat away from the device. The addition of aluminium heat pipes or heat sinks to the concerned case offers a lower thermal impedance path to air. This reduces operating temperature, greatly improving its longer-term reliability.
Intrinsic safety considerations
Intrinsic safety refers to a designed explosion protection method shielding the electrical circuit. Intrinsically safe systems restrict energy even when there are multiple failure conditions. These barriers are employed to restrict the energy discharged if a component or wiring fails. The aim is to stop ignition. A few recommendations for intrinsic safety design are described in the following content.
Batteries used must be sufficiently robust to survive anticipated environmental conditions. There should be minimal electrolyte leakage, which can happen during severe short-circuit environments.
Energy-storing parts like capacitors, inductors, and ferrite beads can be vulnerable to compliance with spark-ignition parameters. The stored available energy in them must be restricted so that there is insufficient energy to ignite an explosive atmosphere. Encapsulation is used to shield circuits against any chances of spark ignition.
Conformal coatings are essential to enhance the long-term performance and reliability of electronic assemblies. The product offers enhanced protection against dust, shock, vibration, chemicals, dirt, abrasion, fungus, moisture, and mechanical stress. Conformal coatings include: one part UV curing formulations, one and two-part silicones, one and two-part epoxies, and a specialized, cost-effective latex system.
To learn more about safety tips in harsh industrial environments, download the e-book The Ultimate Guide to Harsh Environment Ratings & Design.
Ingress protection (IP) and NEMA Ratings
A sealed enclosure is used to prevent the ingress of water or dust. The sealed-off volume of space is used to safe-house electronics within harsh environments. The contextual standard is IEC 60529, as defined by the International Electrotechnical Commission (IEC). This standard designates the number of types and degrees of protection afforded by an enclosure to its electrical equipment. The IP code itself bears the form “IP XY,” where the digits X and Y denote protection from particle ingress and water, respectively. They are commonly used for applications exposed to the elements, along with dust or moisture. Typical user industries include marine, offshore oil and gas platforms, security, lighting, leisure, and food processing.
The National Electrical Manufacturers Association (NEMA) offers a popular protective enclosures standard similar to IP Code (IEC 60529). The NEMA 250 covers a wider sweep of harsh conditions than the IP code. It also includes ratings, both hazardous and non-hazardous, for indoor and outdoor locations. Such conditions include the ingress of foreign objects (like dust or fibres), water, and corrosive agents, including various gases and atmospheres. AE1360 is an example of IP66, NEMA 4 metal enclosure for electrical use in a harsh industrial environment.