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Tasks for which removable memory devices are used include the transfer or storage of files, a means of implementing software or firmware upgrades and for user authentication purposes. The most common removable memory device is the USB stick (thumb drive), launched in 1997. It is hugely popular in the commercial sector, for general IT and infotainment, for example. However, there are several drawbacks associated with using USB drives in the industrial sector.
When designing an industrial system that will interface with a removable memory device it is essential to consider the following points. For convenience we shall illustrate the disadvantages of commercial USB drives against the benefits of bespoke form factor removable memory devices, developed for industrial applications. Before doing so it is worth stating that so widely accepted is the USB stick that we often hear from even experienced engineers that they never knew there even was an alternative to USB.
For industrial applications, the environment is much harsher than in commercial/consumer sectors. Even for a typical manufacturing application, line-side process and control equipment must contend with temperatures, moisture and vibration levels not found in the home or office. Push into sectors like defence and renewable energies (e.g. solar and wind farms) and some of the parameters become extremes. USB flash drives and their corresponding receptables are unsuitable for harsh environment applications.
Conversely, industrial removable memory devices and receptacles are available that were designed for the ‘hard life’. For example, IP67-rated panel-mount receptacles are available for applications where moisture is problem or risk. Also, the physical interface between device and receptable is far better (with some devices locking into place – see Figure 1), so surviving long-term high vibration levels and mechanical shocks is far more likely. Also, the devices cannot be accidentally dislodged.
Depending on the application, the memory devices might be inserted and removed several times a day, and in this respect, USB is only rated for up to 1,500 connect/disconnect cycles. Granted, you are likely to get more than that, but if a thumb drive is to be used ten times a day for 48 five-day weeks that totals 2,400 connect/disconnect cycles, and you enter the realms of uncertainly in less than eight months.
Figure 1 – A panel-mounted receptacle and key. The key must be inserted and turned through 90 degrees for the electrical connections to be made. Once turned, the key is locked in place and can’t be accidently dislodged.
Conversely, industrial removable memory devices (and their corresponding receptacles) are available that are rated up to 200,000 connects/disconnects, so more than 83 years under the same scenario.
Though it feels like USB and other commercial removable memory devices – such as Secure Digital (SD) – have been around forever they are both survivors in the evolution of removable flash memory devices. Many other form factors have come and gone over the years (see Figure 2). Also, the survivors have been through various iterations, and backwards compatibility between a new device and an older reader is not supported; not without making software/firmware modifications.
Devices intended for industrial applications became available in the late 1980s, some 10 years before USB took off, and have remained physically and (largely) electronically unchanged since. Their long-term availability looks good too, whereas in the commercial sector the popularity of cloud storage is likely to reduce the need for (and by association the availability of) USB drives.
By virtue of providing access to a system for communications purposes, USB ports are a potential weakness in terms of security. This was demonstrated most clearly almost a decade ago when the Stuxnet virus was allegedly introduced, via USB memory stick, to Iran’s Natanz nuclear facility. Since then many industries have banned the use of USB thumb drives and some companies have made possession a sackable offense.
Figure 2 – A comparison of the emergence (and in some cases demise) of removable memory device formats.
In addition, if a USB drive containing sensitive information were to be lost or stolen, then unless the data is encrypted, anyone with a computer could read it. Conversely, if a bespoke form factor removable memory device were to be found it is extremely unlikely the finder would have a receptacle with which to interface with the device. Also, anyone wishing to introduce malware into a system via a receptacle intended for a bespoke form factor drive would need the correct device.
Unlike USB sticks, industrial removable memory devices are only available through authorised and reputable distributors.
There has been much in the press during recent years about ‘fake’ USB memory devices, that contain only a fraction of the memory capacity claimed by their markings and receipt-of-sales paperwork. Unless the capacity is verified before the devices are used this could cause problems in the field; for example, in a data logging scenario, the device would become full sooner than desired. Also, what else about the device’s markings is untrue? Again, industrial memory devices are only available through reputable distributors.
No to USB
The flaws with, and risks associated with using, commercial USB devices in industrial applications are many, yet it is amazing how often this is done. The operational life, performance and security of many systems – which may cost several thousand pounds – are frequently compromised when USB sticks, ordered online or even picked up at a supermarket, are used.
As part of the system design process, if the operating environment, the frequency with which devices will be inserted and removed, the intended product life and security are all factored in then the inescapable conclusion is that industrial applications need industrial devices.
For more information, visit www.nexusindustrialmemory.com
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