Industrial - Sensors - PMM

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Platinum sensors for auto emissions control


An auto engine must receive the correct mixture of air and fuel in order for the vehicle's autocatalyst to be fully effective in converting pollutants in the exhaust into harmless gases. Oxygen sensors, also known as Lambda or Exhaust Gas Oxygen (EGO) sensors, use platinum and are a central component of the engine control system in a catalyst-equipped vehicle.

By monitoring oxygen levels in the exhaust gases, the sensors provide essential feedback to the electronic engine management system which controls the air to fuel ratio. The oxygen sensor contains a ceramic body with a platinum tip. It is the function of the tip to detect tiny changes in oxygen levels within the exhaust gas stream. Oxygen sensors are also used to check vehicle emissions as part of  vehicle inspection and maintenance systems.

Sensors which detect the presence of oxides of nitrogen (NOx) in exhaust contain both platinum and rhodium and work on a similar principle to the basic oxygen sensor. They are used in conjunction with specialised autocatalysts to control levels of NOx from lean burn gasoline and diesel engines.

Other platinum sensors in vehicles 

Platinum is used as a bonding wire in climate control sensors. They detect CO and NOx concentrations inside the vehicle and automatically adjust ventilation systems to suit. Air-mass flow sensors employ platinum wire to measure the air-flow to each bank of cylinders in the engine. Air bags contain an initiator sensor, which uses a fine platinum wire coated with explosive material to facilitate release of the air bag.

Platinum sensors in buildings

CO detectors based on platinum are common safety features in homes and industrial buildings. These are small electrochemical devices which measure the current generated by the oxidation of CO at a working electrode - the current produced is proportional to the amount of gas, so allowing the concentration to be monitored. Platinum is used because the cell electrolyte is usually acidic and would corrode other metals.

Medical sensors

Platinum wire, foil and discs are used as electrodes for various sensors in medical equipment. Platinum sensors are used to measure the amount of oxygen dissolved in a solution and to control the addition of oxygen into a biological effluent system. This is particularly important in the analysis of blood gases.