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Diesel oil gets mucky very quickly – because it holds the soot produced during combustion in suspension.
The trouble with the soot is that it tends to soak up the additives in the oil which are designed to minimise engine wear.
So, Delphi have designed a sensor for measuring oil quality – whether it has deteriorated through age or because there is a problem with the engine. It works by measuring AC conductivity at frequencies of between 2 and 5 MHz. It also measures dielectric constant.
[Dielectrics are used in capacitors – the material which separates the plates. A capacitor varies in its ability to store electric charge and this depends on that material separating the plates. This variation is used to give each insulating material its own dielectric constant. Air has a dielectric constant of 1 and other dielectric constants are decided with reference to air].
This means the sensor uses the oil as a dielectric and notes changes in its behaviour to assess condition.
If oil quality deteriorates beyond the specified limits then the sensor can trigger a warning light. It can also allow the oil to be changed when it actually needs changing, according to particular vehicle use.
The sensor is suitable for the engines of cars, big trucks and off road plant.
Delphi have also developed an ammonia sensor which, amazingly, detects the amount of ammonia in the exhaust emissions of vehicles (mainly heavy goods vehicles, at the moment) which are fitted with SCR. SCR is Selective Catalytic Reduction which is used to clean up the NOx emissions of diesel engines. The addition of ammonia converts the NOx into less harmful nitrogen and water.
The sensor will detect the amount of excess ammonia which is being expelled with the exhaust gas so the amount added to the exhaust initially can be reduced and hence the amount released to the atmosphere. Lovely eye-watering smell, ammonia.
© Vanessa Guyll, June 08 | 