ABSTRACT
Voice Recognition 66 Word Boundary Detection 66 Feature Extraction 66 Pattern Standardization and Normalization 68 Word Matching 68 High-Level Linguistic Components 69
Practical Implementation 69 Bibliography 70
1.8 WIRING PRACTICES AND SIGNAL CONDITIONING 71
Introduction 71 Electric Noise 71
Reduction of Noise 71 Noise Types 72 Noise Sources 72
Grounding, Wiring, Filtering 74 Ground Systems 74 Wiring 75 Filtering 78
Applications 78 Transducer Signals 78 Common-Mode Rejection Measurement 80 Thermocouple Signals 81 Low-Level Signal Multiplexing 82 A/D Converters 86
Conclusions 86 References 87 Bibliography 87
INTRODUCTION
Instruments are manmade devices that measure the parameters of physical variables. They may be analog, digital, or a combination of the two. Nowadays, most instruments are digital because of their advantages over analog counterparts. However, the front ends of many instruments are still analog; that is, most signals from sensors and transducers and the first stage of signal processing are still analog. Nevertheless, it is important to mention that in recent years digital instruments operating purely on digital principles have been developing fast. Today’s smart sensors based on digital principles contain the complete signal condition circuits and the sensors in a single chip. The outputs of smart sensors can directly be interfaced with other digital devices.
