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The new Bosch oxygen sensor for heating appliances
The new Bosch oxygen sensor for heating appliancesKeywords: Gas sensors, Oxygen, Bosch
Improved heating appliance efficiency and the reduction of harmful exhaust gas emissions can be achieved by using a new oxygen sensor from Bosch.
Building on the success of the Lambda Sensor, which has proved itself as a standard setter in industrial applications, Bosch engineers have developed an oxygen sensor specifically for use in gas and oil burners. The LSU1 oxygen sensor is capable of evaluating the composition of waste gas emissions and can be used for electronic control in heating appliances.
The oxygen sensor is fitted into the exhaust gas pipe of the heating appliance and connected to a special electronic control unit via a five-pole plug. A heating element integrated into the component ensures that the "exhaust gas nose" operates at all times at an optimum working temperature of 600°C.
The heart of the sensor consists of two measuring cells of ceramic material – zirconium dioxide. The characteristic of these cells is that, at high temperatures, oxygen ions are diffused through the material as soon as differences in the oxygen partial pressure occur at both ends of the cell. This effect is employed in the new oxygen sensor, which uses one cell to measure the concentration of oxygen in the exhaust gas and compares the measured value with the oxygen content of the ambient air. A second cell is then triggered, which pumps oxygen out of the sensor.
This effect is achieved by applying an electrical current to the ceramic material of the sensor so that oxygen ions are diffused from the cathode side to the anode side of the ceramic material. The current used for operating the pump cell varies in strength according to the composition of the exhaust gases and can therefore be used as a measured variable for controlling the heating appliance.
With the help of the Bosch oxygen sensor the fuel/air ratio – which is usually fixed – can be governed by an electronic unit. In the case of gas burners, the oxygen sensor could also be used for identifying the type of gas and thus automatically adapting the burner to meet fluctuations in the quality of the gas. Since the new oxygen sensor must be operated by means of an electronic system, Bosch offers an evaluation circuit element for test purposes. An integrated circuit has been developed for series production, which assumes the entire electronic control function of the sensor.
Contact: Christiane Lechler, Robert Bosch Limited, Meridian South, Meridian Business Park, Braunstone, Leicester, LE3 2WY, UK. Tel: +44 (0)116 281 4488.