SENSORS & TRANSDUCERS FEATURE


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 employ a porous twisted cable connected to a relay panel. When present, water 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


Sensors give


companies enough time to resolve problems before there is any interruption in service."


the cable over time by oxidation and algae growth build up. Some cabinets also have been fitted with float switches which require relatively large 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 off the inside of the sensor tip. 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-inch thread housings. Their specified temperature range spans from -45°C to +125°C, with up to 1A switching so that heavy duty operation in adverse conditions is assured. The sensor can connect directly with the telecoms system through its transistor NPN or PNP output - making installation 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 currently engaged with SST in the testing phase of a custom designed sensor project.


SST Sensing www.sstsensing.com


pressure sensors KELLER (UK) Ltd.


Dorset Green Technology Park, Winfrith Newburgh, Dorchester, DT2 8ZB UK and Ireland: T. 0845 643 2855 F. 0845 643 2866 E-Mail: sales@keller-pressure.co.uk Web: www.keller-pressure.co.uk www.keller-druck.com


PIEZORESISTIVE OEM PRESSURE


TRANSMITTER 4 LD9LD WITH I²C INTERFACE AND EMBEDDED SIGNAL CONDITIONING


 No external components


 Ranges 01 bar thru to 0200 bar  Accuracy, error band +/- 0,5%, 050 °C


 Sizes Ø 11 m, 15 mm, 17 mm, 19 mm bar  Very low power consumption


PRECISION PRESSURE TRANSMITTER 33 X


 Ranges 00,2 bar thru to 01000 bar, adjustable  Output signals: 420 mA, 010 V, RS485 Digital  Mathematical on-board error correction  Accuracy, error band 0,1 %FS, 1040 °C  Optional enhanced precision to ±0,01 %FS


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