1.3 Terminology; Analog Value - A; Digital Value - D; Figure 1 - Analog Value Is Continuous In Time And Value - Honeywell 2MLF-RD4A User Manual

1.3 Terminology

The terminology used in this document is as follows:
Analog value – A
A physical quantity like temperature, pressure, speed, current, and so on, which changes
continuously with time, is called an analog value. The PLC cannot process an analog
quantity. The RTD input module converts analog input temperature value to
corresponding digital value which then can be processed by the PLC.
Figure 1 – Analog value is continuous in time and value
For example, temperature changes continuously with time, as shown in Figure 1.

Digital value - D

In a digital electronic circuit, data is processed and saved in the form of numbers 0 and 1.
The data is processed as a string of 0s and 1s. For example, ON and OFF signals displays
as 1 and 0, respectively, in a digital system. This is called as the binary numbering
system. Decimals stored in binary format are called Binary Coded Decimals (BCD).
BCD is thus a digital value. Figure 2 displays the digital value of the physical parameter
(temperature).
R200 Resistance Temperature Detector 2MLF-RD4A User's Guide
September 2010 Honeywell
1. Introduction
1.3. Terminology
19