Feature: Sensor enclosures
The engineer’s guide to specifying plastic enclosures for IIoT sensors
By Robert Cox, Marketing Director, OKW Enclosures T
he use of sensors in Industry 4.0 setups is growing at an exponential rate. T is is translating into a surge in the number of plastic enclosures developed
principally for IoT/IIoT, smart factories and other locations where metal housings would have previously been the fi rst choice. Today, plastics are the preferred option.
Enclosure materials Plastic enclosures for sensors must be reasonably tough. Although not always directly in the fi ring line, their durability is a prerequisite. In the past, ABS was the plastic of choice for enclosures due to its high impact resistance, good dimensional stability and near excellent tensile strength. However, ABS is vulnerable to UV rays, which discolour and degrade the plastic and make it brittle. A more UV stable plastic is
ASA. It replaces the UV-vulnerable butadiene rubber found in ABS with an
38 October 2025
www.electronicsworld.co.uk
acrylate rubber that copes better with ultraviolet light. Better still is an ASA/PC blend that adds
polycarbonate for extra impact resistance. Polycarbonate’s reputation for strength is well founded – it is specifi ed for riot shields and bulletproof glass. T is blend is not only strong and UV stable, but it off ers UL 94 V-0 fl ammability resistance, outperforming UL 94 HB plastics. Small, fast-fi t sensor enclosures are
typically moulded from ASA+PC, but they also must provide good ingress protection (IP 65) as a matter of course; for complete protection against dust ingress, as indicated by the ‘6’, and ‘5’ shows that the enclosures can resist low- pressure water jets from any direction. T e IP 65 rating is based on a 15-minute test in which an enclosure is sprayed with 12.5 litres of water per minute (30kPa at a distance of three metres). OKW’s small, fast-fi t sensor enclosures,
such as MINI-DATA-BOX and EASYTEC, are moulded from ASA+PC as standard.
T ey also off er good ingress protection to IP 65 rating.
Wireless connectivity guaranteed T e proliferation of sensors in IIoT environments means that most must be wireless, for fl exible deployment. Most engineering-grade plastics such as ABS, PC and ASA are RF transparent, although this in turn raises EMI/RFI concerns, especially in environments packed with wireless sensors, actuators, gateways, access points, controllers, RFID readers, NFC tags and machine-to-machine (M2M) links. RF transparency means that an
antenna can be placed inside the enclosure. Alternatively, the flat sides can be machined to accommodate an external antenna should that be required for greater range and/or enhanced signal reliability. Opting for an external antenna can also overcome some EMI/RFI interference problems – it is free to radiate signals outside the EMI-shielded enclosure.
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