Gert van der Horn – författare

The calibration procedure that is required for manufacturing accurate sensors is, presently, time-consuming and difficult to automate. Hence, it contributes considerably to the sensor fabrication costs. This text explains how to include a digitally programmable calibration feature in an integrated smart sensor. Several related topics are discussed as well, including calibration and linearization techniques. Calibration circuits using analogue signal processing, digital signal processing, or a mixed-mode technique based on sigma-delta modulation are presented, as well as the other circuits needed in a smart sensor. The combination of a programmable calibration circuit and a digital bus interface, integrated together with the sensor, enables automation of the calibration procedure for a large batch of such integrated smart sensors at a time. This will help to reduce the costs of the sensor calibration, and, thus, to decrease the price per sensor, in particular for mass-produced sensors. The work should be of interest to analogue design engineers, researchers and students. It can also be used as an advanced text on the subject.

1 1. 1 Introduction The (signal processing and storage) capacity ofthe human brain enables us to become powerful autonomous beings, but only if our brains operate in conjunction with (at least some of) our senses and muscles. Using these organs, we can interact with our environment, learn to adapt, and improve important aspects of our life. Similarly, the signal processing capabilities of modern electronics (computers) could be combined with electronic sensors and actuators to enable interaction with, and adaptation to, the (non-electrical) environment. This willlead to smarter and more powerful automated tools and machines. To facilitate and stimulate such a development, easy-to-use low-cost sensors are needed. The combination of electronic interface functions and a sensor in an integrated smart sensor, that provides a standard, digital, and bus-compatible output, would simplify the connection of sensors to standard electronic signal processors (microcontrollers, computers, etc. ). Currently, the calibration procedure, required for standardization of the sensor output signal level, contributes largely to the production costs of accurate sensors. To enable automation of the calibration procedure, and hence reduce the sensor fabrication costs, a digital calibrationjunction should be included in the smart sensor. INTEGRATED SMART SENSORS: Design and Calibration Introduction 1. 2 Sensors and actuators In industry many processes are electronically controlled. As depicted in Fig.