Making sensors for harsh environments is not straightforward, and designers working on them can expect some challenges along the way. Here are some strategies for designing sensors and ensuring they’re well-protected.
Understand industry-specific requirements
A good starting point is to understand the particular stresses the sensor will encounter during normal use. For example, the things that could damage poorly designed sensors will differ for those used in the oil and gas industry versus aerospace.
Dana Holmes, global business development manager for sensors at Banner Engineering, explained some of the specifics that constitute a harsh environment in the food and beverage industry. “Harsh environments can imply a washdown environment in the food and beverage industry or it can just mean a setting subject to vibration or temperature swings. But when engineers refer to extreme environments, they typically mean washdown-type settings — as that’s where most end users need rugged sensors,” she said.
Holmes explained some of the specific steps her company takes to protect its sensors. “We manufacture sensors aimed specifically at satisfying specific [ingress protection] ratings needed for these environments. Some of our sensors also include features to support hygienic conditions — to prevent debris buildup and the growth of bacteria. We also put potting material inside certain sensors to help them withstand temperature cycling.”
Certain industries also need sensors that must work reliably with limited human monitoring, such as when companies deploy them in areas not safe for people except for short periods. In such cases, the sensors must be well-safeguarded from the expected elements, and they may require batteries that can last for years.
Speaking to clients to determine the essential requirements for harsh-environment sensors will ensure engineers have their bases covered. It’s also useful to ask those parties what their experiences have been when using other sensors and, most importantly, how they fell short.
Explore conformal coating options
When applied correctly to sensitive electronic components, conformal coatings form a tight bond that’s only micrometers thick and stop moisture and vapors from harming the parts. These coatings have specific formulas and structures that make them work.
Acrylic conformal coatings can go onto the electronics via spraying, dipping or brushing and keep their shape during the curing process. This coating may be a good choice if the sensor needs protection from humidity and fungus. However, acrylic coatings are more likely to break down at high temperatures than other options. Moreover, they require a thicker application to ensure the required effectiveness. These factors and others have made them gradually less popular over the years.
Epoxy coatings get applied the same way as acrylic ones. Additionally, these options provide excellent abrasion and chemical resistance, as well as protection against humidity. However, they do not offer robust safeguards against temperature extremes. One of the downsides of this coating is its potential to shrink during the polymerization process.
Silicone coatings are another widely used conformal coating option. People can customize them to a product’s needs, such as by making them elastomeric for stress-relieving purposes or more rigid and durable. Additionally, these coatings adhere to substrates well and protect them from ultraviolet light, moisture, humidity and temperature extremes. However, silicone is like some other coatings in that people must apply it relatively thickly, which may mean it’s not an ideal choice for some sensors.
Parylene is another possibility. It can tolerate temperature extremes and physical stress and provides uniform coverage to prevent leakage. However, this coating is applied with chemical vapor deposition, so it’s associated with higher manufacturing costs than the other options. In any case, people who take the time to weigh the pros and cons of specific conformal coatings for their sensors make practical efforts to protect them.
Consider how simulations could help
Simulations could accelerate the design process of sensors for harsh environments. Sensors used in industrial environments assist with essential needs, such as remote machine monitoring. Decision-makers must feel confident in their reliability, and good design and protection from the elements help create that trust.
Simulation tools won’t uncover all relevant insights, but they could support designers in addressing potential issues not previously considered. That’s especially true when sensors must last for a product’s life span, which could be decades. Think about the sensors used in connected cars. The environments they’re exposed to vary significantly depending in which markets the automotive brand operates. How might the sensors fare if exposed to a dust storm versus subzero temperatures and blizzards?
Warren Ahner, CEO of simulation software provider RightHook, noted, “Precipitation such as rain and snow can definitely reduce the performance of a lidar sensor. They are particularly affected due to the beam divergence and the short pulse duration. Snow detection noise is really concentrated near that sensor and manifests itself in these kinds of large clusters.”
He continued, “What we see is snow cluster noise really introduces false detection, as well as obscures important obstacles, leading to some really, really critical false-negative situations, and you really get into that once you start approaching this 3-to-4-feet of snow accumulation an hour [rate].” However, Ahner said if the snowfall speed is less, creating a 30-second simulation could take hours. Therefore, his company uses empirical data models on top of the simulations that work as noise models.
Simulations won’t reveal every possible aspect of conditions future sensors might face. However, they can help designers evaluate all likely harsh environments that could affect the sensors. Knowing those details makes it easier to plan how to protect them.
Sensors for harsh environments require special considerations
Designing a sensor is always an intricate task, but there are even more things to consider when the people involved know the products will or may be exposed to demanding settings. Failing to adequately protect a sensor from the effects of high temperatures, moisture or other outside factors could make it malfunction, have a shorter-than-expected life span or even cause accidents that harm people. Taking a thoughtful approach at all stages of the creation process helps prevent these adverse outcomes.
Emily Newton is a technical writer and the Editor-in-Chief of Revolutionized. She enjoys researching and writing about how technology is changing the industrial sector.