Chapter 1. INTRODUCTION
1 - 2
[ Fig 1.1] Analog Value
[Fig 1.2] Transducer
1.2.1 A-Analog Value
Analog value is a sequentially changing value such as voltage, current, temperature, speed, pressure, flux, etc.
Temperature, for example, is sequentially changing according to the time. Because this temperature is not input
on the PLC through transducer, the same analog value of DC voltage (0 to
±
10 V) or current (4 to 20 mA) in
accordance with the temperature should be inputted on the PLC.
1.2.2 D-Digital Value
Digital value is non-sequentially changing value written as the number like 0,
1, 2, 3. The signal of on or off is written as digital value of 0 or 1.
There are BCD value and binary value in the range of digital value.
Analog value isn't written directly onto the CPU. For analog input to the
CPU operation, analog converted to digital value has to be inputted onto
the CPU and for analog output, the digital value of the CPU should be
converted to analog value.
1.2 Glossary
Transducer
Analog input
0 to
±
10 V or
0 to
±
20 mA
Analog output
0 to
±
10 V or
0 to
±
20 mA
[Fig 1.3] Digital Value
[Fig 1.4] PLC Processing
Time