Conversion Between Digital and Analog
The overall structure of a computer controller often fits the pattern shown in Fig. 8-1. The transducers and status sensors provide voltages to the analog channels of a multiplexer (MUX). The MUX selects one of these channels at a time and sends that signal on to the analog-to-digital converter (ADC), which feeds a binary number of perhaps eight bits to the microcomputer. Acting in accordance with the program stored in the microcomputer by the user, the microcomputer takes action based on this program and the signal received. This action may be to output an 8-bit binary number that can be converted to a voltage by a digital-to-analog converter (DAC). In other cases the output of a single bit may be all that is necessary to activate one of the actuator devices discussed in Chapter 8. If there is more than one actuator, a MUX transfers the voltage from the DAC to the appropriate channel. Since the MUX is connected momentarily to only one channel, the signal leaving the MUX is as shown in Fig. 8-2. The voltage appears as a series of pulses, but the actuator will need a continuous signal. A “sample-and-hold” device in the circuit following the MUX will provide a continuous voltage to the actuator at a magnitude of the last pulse delivered by the DAC.
KeywordsInput Voltage Digital Number Binary Number Digital Output Clock Pulse
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