Page 303 - Sensors and Control Systems in Manufacturing

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Cha p te r
F i v e

The most significant aspects of selecting A/D hardware are:
• Number of input channels
• Single-ended or differential input
• Sampling rate (in samples per second)
• Resolution (in bits)
• Input range (specified as full-scale volts)
• Noise and nonlinearity
5.7.4.2 Analog Output
A digital-to-analog (D/A) converter changes digital information into
a corresponding analog voltage or current. This conversion allows
the computer to control real-world events.
Analog output may directly control equipment in a process that is
then measured as an analog input. It is possible to perform a closed
loop or proportional integral-differential (PID) control with this
function. Analog output can also generate waveforms in a function
generator (Fig. 5.12).
5.7.4.3 Digital Input and Output
Digital input and output are useful in many applications, such as
contact closure and switch status monitoring, industrial ON/OFF
control, and digital communication (Fig. 5.13).

Digital Code

D0 Analog Signal
D1
D/A Driver
Converter
D15

FIGURE 5.12 Analog output.

Your PC

Valve
SSR Series Board
Digital I/O Board

FIGURE 5.13 Application of digital input/output.