Converter Digital-Analog

With temperature, we can use a thermocouple, which typically has a resolution on the order of 0.05 mV/°C. (We could always use a RTD for better resolution and response time.) That is too small a change in output for most 12-bit analog-digital converters, so we must have an amplifier to boost the signal. This is something we do in a lab, but commercially, we should find off-the-... 

Fig. 14.9. Schematic representation of the analog-to-digital conversion process. The continuous analog signal output by the detector is sampled, converted into digital data points and transferred to the data system.

The rate meter provides the required high voltage for (he photomultiplier iibes and converts the digital signal obtained from the scintillation crystal to an analog output for the recorder. 

The major amount of HPLC separations is performed with re versed-phase columns employing binary or tertiary solvent mixtures with isocratic or gradient elution. The protons of the solvents of the mobile phase cause severe problems for an adequate NMR registration. The receiver of the NMR instrument (either a 12-bit or a 16-bit analog-digital converter (ADC)) is unable to handle the intense solvent signals and the weak substance signals at the same time. 

After the anti-aliasing filter, the analog/digital converter (ADC) quantizes the continuous input into discrete levels. ADC technology has shown considerable improvement in recent years due to the development of oversampling and noise-shaping converters. However, a look at the previous technologies [Blesser, 1978] [Blesser and Kates, 1978][Fielder, 1989] will help appreciate the current state-of-the-art. 

A/D Converter Analog to digital converter changes a variable... 

Fig. 8.8 Successive approximation converter (DAC digital-to-analog converter, SAR successive approximation register).

The rapid development of solid-state electronic devices in the last two decades has had a profound effect on measurement capabilities in chemistry and other scientific fields. In this chapter we consider some of the physical aspects of the construction and function of electronic components such as resistors, capacitors, inductors, diodes, and transistors. The integration of these into small operational amplifier circuits is discussed, and various measurement applications are described. The use of these circuit elements in analog-to-digital converters and digital multimeters is emphasized in this chapter, but modern integrated circuits (ICs) have also greatly improved the capabilities of oscilloscopes, frequency counters, and other electronic instruments discussed in Chapter XIX. Finally, the use of potentiometers and bridge circuits, employed in a number of experiments in this text, is covered in the present chapter. 

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