Novotechnik RFC4800 position sensor used in taxis

Despite their rather quaint appearance, London Taxis are expected to meet all the current legislation regarding exhaust emissions. Many of these vehicles are now equipped with an exhaust gas recirculation (EGR) system that utilises a new type of magnetic position sensor developed by Novotechnik of Stuttgart, Germany.

The Novotechnik RFC4800 sensor is used to monitor the position of the diesel injector, effectively measuring the fuel demand. The sensor itself is a two-part magnetic unit that has a resolution of 12 bits and a linearity (accuracy) of 0.3 per cent. The two-part construction makes integration of the unit extremely simple.

With its absolute output, the sensor will know exactly where it is at all times, even if the engine is stopped and re-started. Being rugged enough to stand up to the harshest of environments, and with no moving contact, the sensors will not suffer premature wear due to vibration.

The output from the sensor is fed into a control system that monitors fresh air, exhaust gas and fuel demand, and recycles some of the exhaust back into the inlet manifold. The advantage of this is that the fuel mixture burns at a lower temperature and burns more completely so that the exhaust gasses contain less particulates and other impurities. From the operator's point of view, the big advantage is that the taxi's useful life is extended without any additional costs for special additives or fuels.

Variohm EuroSensor is the UK distributor for Novotechnik, which manufactures the RFC4800 and many other sensors.