Microelectronic sensors

Most control systems consist of a chain of three functionally different components:

• Sensors that take in information and convert it into electrical values;

• lastructure for electronic processing of digital or analog signals ;

• motors that act on the environment or inform the human operator.

In the 1970s, with the considerable evolution in performance and the reduction in manufacturing costs for processing electronics (essentially linked to microprocessors), sensors became strategic products, largely determining the cost price and efficiency of control systems. What's more, increased performance (involving compensation for thermal drift and signal linearization) and the need to reduce the cost of interfacing with the processing unit (leading to digitization and control of a communication bus) meant that the sensor itself had to be combined with electronics comprising analog and digital circuits. Together, they form an intelligent sensor.

The sensor's problem can then be summed up in the following objectives:

• cost reduction ;

• compatibility with electronic circuits ;

• miniaturization.

Microelectronics techniques provide a solution based on the collective nature of the processes (hence the low costs), the reduction in dimensions and the possibility of producing the sensor and its electronics on the same substrate.

It should be emphasized that the federative aspect of these techniques is essential; because of their wide diversity and still small markets, sensors cannot justify a specific production investment that could not be amortized. It is essential, to the detriment of performance, to make do with production resources that have already been mastered.