Low Power Radio in the Water Industry
Low power radio (SRD) technology has for many years been used in the water industry as a bridge between remote sensors and actuators and the central SCADA and control systems. Applications include remote meter reading, sewer block detection, water leakage reporting, CSO spill reporting (Combined Sewer Overflow), wireless sensors and anti-pollution valve control. Due to the complex nature of the environment in which many of the devices have to operate designers of the opinion that at the sensor level there is no protocol or operating frequency that could be adopted carte blanch across the industry. Taking the example of blocked sewers and other subterranean communications – these have been proven to operate better at low radio frequencies – where often the manhole cover is converted into a passive radiator. Further, due to restricted access and the lack of mains power battery operation requires that radio protocols have to be ultra lean to minimise the length of the transmission and thus power consumption. Peak radiated power levels also need to be considered as these are linked to current bursts levels and when ATEX certification is involved can lead to problems, Mesh networks are the vogue in above ground networks – however seldom are practical for below ground operation as signals generally only radiate upwards and very little if anything goes sideways to a neighbouring network node. This means that the best topology tends to be star hubs, with a receiver is mounted on at a high location looking down over the network.