FEATURE SENSORS & TRANSDUCERS
IR-BASED LIQUID DETECTION TECHNOLOGY to protect telecom hardware from catastrophic failure
Andrew Cumming, SST Sensing, discusses how optical based liquid level sensors are being used to ensure telecommunication equipment is protected for leaks
O
utdoor telecom equipment, including mobile base stations, cabling
cabinets and battery backup systems, is potentially in danger of being damaged by exposure to water ingress. This can be due to leaks, condensation build up, vandalism or damaged enclosure heating/ventilation systems. Sensitive and expensive electronic
components can subsequently come into contact with sensitive electronics components. If water build-up within the cabinet goes unnoticed it can lead to network downtime. Such circumstances have a huge impact on a telecom operator’s business, not only effecting its profit margins and engineering resources, but also its long- term reputation in the industry. It is therefore necessary for telecommunications companies to take preventative measures in order to safeguard against the threat of potential water leaks causing such catastrophic damage. In the past telecom companies could only react to these situations when they happened. By then of course it was generally too late, as the network’s operation would have already been compromised. In an attempt to tackle this, regular inspection of their network infrastructure would be carried out to
pre-empt any potential issues. This, however required a large number of field staff to conduct the work in often pole-mounted remote rural locations, travelling considerable distances to repair blown equipment. A less costly and logistically more effective strategy that has now been tried, tested and approved by major telecommunication providers is to implement a leak detection sensor technology within the enclosures where telecoms equipment is being housed. This means that if water leaks occur and sensitive electronic systems are put under threat then the telecom company can be made aware of things much earlier on - giving it enough time to resolve the problem before there is any interruption in service. Consequently subscribers do not become annoyed and brand image is not impinged upon. The key attributes that sensors need to
possess to be suitable for this application scenario are: operational robustness; EMC testing; performance; compact form factor; and long working lifespan.
OPERATIONAL ROBUSTNESS As with any device placed in an uncompromising working environment, it must have a rugged construction and exhibit resilience to the external forces it
is likely to be exposed to. Telecom cabinets can be situated at the top of antenna towers or on rooftops and in some countries the seasonal and diurnal temperature variations can be quite extreme, so this aspect needs to be given adequate consideration.
EMC TESTING To ensure no EMC interference is generated from the sensor and that the presence of electromagnetic generating equipment has no effect on the sensor.
PERFORMANCE The combination of high degrees of accuracy and rapid responsiveness both need to be satisfied when specifying a sensor for leak detection tasks of this nature. The quicker that it can be confirmed that water is entering the telecom cabinet, the more chance there will be that engineering staff can be alerted and appropriate action can be taken before serious damage is done.
Schematic of Optomax liquid level sensing technology - IR light is internally reflected when no liquid is present, then dispersed if liquid builds up around the sensor tip
COMPACT FORM FACTOR As telecoms cabinets will contain large quantities of cabling and electronics, space limitations can often be a factor. The selected sensor therefore needs to have as small dimensions as possible while still being fully functional.
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FEBRUARY 2018 | INSTRUMENTATION
/ INSTRUMENTATION
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