No-power sensors respond when asked

A new sensing system is powered entirely by wireless signals generated by the interrogating equipment. It therefore removes the need for either mains or optical powering or batteries. Applications range from ensuring the proper performance of the equipment on large printing machines through measuring temperatures in hospital hot water systems to human blood sugar monitoring. Richard Little, director of Jenton International, describes its new unpowered sensing system as "nearly RFID". The sensors are normally unpowered and passive, but when approached by an interrogating Pocket PC, they are powered up from it by induced current, identify themselves and deliver a reading of whatever they are measuring. "Our main competitor is conventional technology and working practices - probes, pens, and paper - with all the errors that these can produce," he says. "Our main strength is that we enable fast and accurate measurements of important data to be made. Our main weakness is the capital investment required by the smaller end user." The reason why the system is described as "nearly RFID" is that, for reasons of maximum electromagnetic power transfer efficiency, it uses inductive powering from the interrogating device at a frequency that is not one of the 12 bands normally allocated for RFID devices. Unlike the vibration-powered devices described in the July edition of Eureka, the sensors require no motion to power them. The devices shown to Eureka at the recent Innovention 2006 event in Winchester were only about 20mm square - and could be made much smaller. There has been speculation that RFID devices could be etched onto pieces of silicon about the size of a grain of sand, scattered around and subsequently interrogated. The idea comes from the US defence community as a possible way of tracking potential adversaries by satellite. Others have suggested such devices as a virtually undiscoverable means of tracking stolen cars. Equipped with sensors, however, they could potentially undertake tasks that are more useful without being much larger. Since they have neither batteries nor power generating facilities, the devices need only be large enough to accommodate some fairly simple circuitry and an antenna. The first commercial application is a system of ultra violet sensing radiometers developed with US partner company EIT. The sensors fit onto large printing presses. Prior to starting the day's work, the print shop manager goes round each lamp with a Pocket PC, clicking on the sensor associated with each lamp to establish that it is producing the required amount of ultra violet light. Imbalance between light outputs is liable to lead to unacceptable print results. Another identified application is monitoring piped water temperature in hospitals. This is now performed using temperature probes on the pipes, with considerable consequent inaccuracy in the measured and recorded results. Water quality monitoring has been identified as a potential market, as has weighing sea containers in port or on board ship - much less expensive than a weighbridge. One of the advantages of the system over traditional wired systems is that it avoids interference picked up by cables, without having to go to the expense of optical fibre systems. Because the sensing transducers can potentially be made extremely small, they might also be embedded in the human body, such as for blood sugar level monitoring. The sensor units made by Jenton International cost £70-150 each, depending on application - though it may be possible to supply them much more cheaply for volume applications such as the water temperature monitoring for hospitals. Jenton International's main business is packaging machinery. The sensing technology is one of its spin offs. Innovention 2006 is an annual event organised by the South Hampshire Enterprise Agency. Jenton International Eureka says: This minimalist approach solves an engineering problem in the simplest possible way Pointers * Sensors are powered by the unit that interrogates them * They are designed to function as part of complete monitoring, predictive maintenance and asset management systems