| Popis: |
This chapter deals with precision measurement and sensor conditioning. The high-resolution Σ–Δ measurement ADC has revolutionized the entire area of precision sensor signal conditioning and data acquisition. An important benefit of Σ–Δ ADCs is that they are typically designed on CMOS processes, therefore, they are relatively low cost. Some of the architectural benefits and features of the Σ–Δ measurement ADC are summarized. High-resolution measurement Σ–Δ ADCs find applications in many areas, including process control, sensor conditioning, instrumentation, and so on. The chapter focuses on several representative sensor conditioning examples, which illustrates most of the important application principles. A simple design analysis of a weigh scale based on the AD7730 ADC and a standard load cell is presented. A summary of the final weigh scale design and specifications is provided. Thermocouple conditioning using the AD7793 is discussed. Thermocouples provide accurate temperature measurements over an extremely wide range; however, their relatively small output voltage makes the signal conditioning circuit design difficult. The direct digital temperature measurements and microprocessor substrate temperature sensors are examined. This chapter concludes with a discussion on applications of ADCs in power meters. |
