Industrial and embedded computers today have it rough. We stick them in harsh environments where they’re subjected to constant electronic noise, radiation, and power fluctuations, but how much do we pay attention to how those environmental factors affect our systems?
Compounding the issue are immunity and emission ratings that don’t always cover the areas where you need protection. It can be frustrating and costly to assume you’re covered by an FCC or CE marking, only to discover that your system isn’t protected after it gets zapped by a power outage. How were you supposed to know?
We want to clear up the confusion and help prevent future catastrophe with an overview of the types of immunities and certifications to consider when selecting embedded and industrial systems and what can be done to protect them. This is especially important for applications where immunity is critical, like factory controllers, medical devices, and emergency communication equipment.
What is Immunity Testing?
Immunity testing allows manufacturers to test tolerances to real-world situations. Static discharges, magnetic fields, power dips and fluctuations, fast electrical surges, transients, and broadband radio noise are all forms of interference your system faces on a daily basis. What are they and what do they look like in the real world?
This is caused by changes in polarization from nearby sources. Magnetic interference can be caused by things like inductive smelters or ovens, large motors, or MRI machines and commonly manifest as erased storage devices and inductor damage in power supplies or other components.
Radio frequencies can disrupt embedded systems by interfering with its own operating frequencies. Common suspects include VHF radios or transceivers, like the ones frequently found in busses, police cars, or handheld transceivers. If you’re experiencing standing wave patterns rolling across displays, audio chirps, hums or bursts over line-out connections, lost video syncs, or computer lock-ups, you might need to investigate for RF interference.
Changes in voltage happen more frequently than you think. An HVAC unit kicking on, a power-hungry tool, heavy machinery, or current supplied by a generator can change the amount of power being delivered to your system. If your technology isn’t protected by the right filters, system outage or permanent damage could occur.
Electrical Fast Transients
Long communication lines, like LAN cables, may see electrical surges from other devices or inclement weather. The surges can couple onto the cable and shoot right into your system through its communication ports, zapping it.
Static electricity wreaks havoc on unprotected systems by destroying delicate semiconductors. Installations with low relative humidity, especially during winter months or in high desert environments, present ideal conditions for higher than normal static discharges. Conveyor belts, belt-driven exercise machines, or other devices that create rapid or circular friction are prime suspects for undesired on/offs, hangups, or reboots.
When To Consider Immunity Testing
If you’re stuck trying to discern whether your system is protected, and how, start by looking at its markings. Just make sure you’re looking for the right things. It’s commonly misunderstood that the FCC marking applies to immunity, but it only applies to device emissions.
Instead, look for the CE mark, which covers both emissions and immunity. Here’s the rub, though: having the CE mark doesn’t guarantee the device has been tested properly for immunity. Manufacturers can self-declare that their devices conform to CE standards without testing them, but are required to show proof of compliance if audited.
How do you ensure that the systems you’re buying are protected? The key is to ask the manufacturer for their declaration of conformance for EN 55024 if the CE marking is present. EN 55024 is the Information Technology Equipment Immunity standard and is a safe bet for most computer applications. The declaration can be based on a technical file or lab verification and will give you insight into how the device was tested, its level of immunity, and whether it conforms to other standards.
If the manufacturer has no evidence of compliance, you might consider your own testing or seek out a solution that meets your immunity needs. It’s better not to take the chance that the system is vulnerable.
With a better understanding of the types of interference that can affect your systems, let’s explore the ways we can test and protect them.
How We Test Systems For Immunity
Immunity is a major concern for our customers, so we design our systems to conform to EN 55024 and go through exhaustive testing to exceed those standards. To simulate the noisiest possible scenario, we test the entire device in its most complicated configuration, which includes the power supply and all connectors hooked up to external devices.
Testing begins with a healthy dose of 8,000 volts from a taser (also a great way to blow off steam on a Monday). We drown the system in a magnetic field, feed it horrible power conditions, and blast it with huge amounts of concentrated broad spectrum radio waves with the goal of trying to cause hiccups, power failures, or any non-recoverable condition. It might seem excessive, but these tests exceed the real-world events that happen to our systems every day.
This kind of testing is the most effective way to ensure a system can handle common real-world fault conditions. It’s especially important when it’s known that the equipment will be going near magnetic fields, sparks, or inconsistent power to verify if its level of immunity will actually protect the device.
Fortunately, a lot can also be done through engineering design to protect computer systems from harm.
Our ML400 system being tested for RF interference. All systems go!
The systems we build go into a wide range of applications, so we need to make sure they can take whatever’s dished out. We start with electronics that were designed for the task: we isolate the I/O input signals, separate the chassis and digital grounds, use wide input power with proper filtering, install transient voltage suppressors that ‘eat’ erratic inputs, and employ grounding schemes that bolster the circuit and chassis’s ability to protect the heart and brains of the system.
The next stage of defense comes from the chassis itself. We leverage our industry-leading Hardshell™ Technology to form a protective force-field around the system and use highly conductive nickel plated steel to quickly route discharges to the ground. Double right-angle interfaces at the body panels ensure radio frequencies can’t sneak in or out. We also use laser ablation on contact surfaces to maintain the integrity of the grounding scheme.
We add yet another layer of protection with compressive EMI gaskets, sealing it from emissions and radiation while offering a layer of dust and debris protection. Lastly, we only use top-tier power supplies with international certifications and world power inputs to ensure that proper safety and power filtering defenses are in place.
While there’s a lot to consider when it comes to immunity, we hope this clears up some of the confusion. We take pride in engineering our systems to operate in these kinds of environments and leverage our field experience to help you avoid system failures as a result of adverse environmental factors. To help you keep these factors in mind, click here to download our Device Immunity quick reference guide which covers the types of device immunities, their sources, and the regulatory information that will keep your systems safe.
To learn more about what systems Logic Supply offers that match to your specific application, click here or call US +1 802 861 2300 or EU +31 85 2733760 to get in touch with one of our system experts.
Darek is the Communications Manager at OnLogic. His passion for both journalism and technology has led him from the newsrooms of local papers to the manufacturing floor of IBM. His background in news gathering has him always on the lookout for the latest in emerging tech and the best ways to share that information with readers. In addition to his affinity for words, Darek is a music lover, juggler and huge fan of terrible jokes.