In many applications it is critical to know the presence or absence of fluid. An early indication helps to prevent the loss of critical fluids, damage to equipment, costly service interruption and system downtime. An industry proven solution to these problems is SST’s affordable range of leak detection liquid level switches.
By Andrew Cumming, SST Sensing Ltd.
Outdoor Telecom equipment including mobile base stations, cabling cabinets and battery backup systems, are potentially in danger of being damaged by exposure to water ingress due to leaks, condensation build up, vandalism or damaged enclosure heating/ventilation systems.
Sensitive and expensive electronic components can be protected by immediate warning of water build up within the cabinet that would otherwise go unnoticed and leading 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 been compromised. In an attempt to tackle this, regular inspection of their network infrastructure was 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 mostly 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 immediately be made aware much earlier on – giving it enough time to resolve the problem before there is any interruption in service. Consequently subscribers don’t become annoyed and brand image is not impinged upon.
The key attributes that such sensors need to possess to be suitable for this application scenario are as follows.
- 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 tested- 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.
- 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.
- Long working lifespan – Once a leak detection sensor is installed, whether it be in a telecom cabinet, or in other application settings (such as an industrial automation system, a remote monitor station or a petrochemical pipeline), the likelihood is that it will need to remain there for a prolonged period of time, with little (if any) opportunity for maintenance to be executed. Therefore, ensuring trouble-free operation and no moving parts are of paramount importance.
A commonly used method of liquid detection is to use a porous twisted cable connected to a relay panel. Water when present shorts the twisted cable together causing the relay to trip.
This method allows for long cable runs to be monitored however is inherently problematic in sealed environments as the cable can pick up any moisture in the environment and remain saturated when dew is present. The fitting of the cable using non-conductive fixings can cause false alarms to be initiated. Cable excitation with DC Current can degrade the cable over time by oxidation and algae growth build up. Some cabinets also have been fitted with float switches which require larger amounts of liquid to be present and delay the time taken to detect any ingress.
A far better approach is to use solid state technology. A non-contact optical measurement arrangement allows the various issues that come with cabled systems and float switches to be circumvented – thus presenting a more convenient, responsive and long-lasting solution via which critical telecom hardware can be protected. Through use of its highly advanced Optomax liquid level sensor technology, SST Sensing has been able to provide the telecom industry with low power, low cost sensors that are optimised for this purpose. These work on the principle of infra-red (IR) light being emitted and internally reflected of the inside of the sensor tip (as show in Figure 1). When liquid comes into contact with the sensor tip, the optical characteristics are altered and the reflected light signal changes accordingly (as some light is now dispersed rather than being reflected). Since less light is incident on the sensor device’s phototransistor element, a triggered output is generated. This mechanism means that far smaller quantities of liquid can be detected and field engineers can hence be mobilised quicker. To address the space constraints previously discussed, Optomax liquid detection sensors can be supplied in compact M10 or ½” thread housings. Their specified temperature range spans from -45°C to +125°C, with up to 1A switching so that heavy duty operation in a wide temperature range is assured.
The sensor can connect directly with the telecoms system through its transistor NPN or PNP output – making installation very straightforward to accomplish. By placing the sensor at the lowest point in the cabinet, an alarm can be generated as soon as any water touches the sensor tip.
SST is already working with one of the largest telecom contractors in North America, supporting the widespread roll-out of its IR sensors into telecom cabinets for major network operators in the region. Another large contractor is working with SST in the testing phase of a custom designed sensor.
For more information on SST’s liquid level switches, please Ask the Expert today!