1. MicroLogix Packaged Controllers
Programmable Controller Basics Analog Control
MicroLogix Packaged Controllers 1

2. What is an Analog Signal?g I/O
Analog Signal: The representation of numerical quantities by the measurement of continuous physical variables.

3. Answer
Unlike Discrete signals, which have only 2 states (ON and OFF). Analog signals can have an infinite number of states.
Temperature is an example of an analog signal. This signal is constantly changing by infinitesimal amounts. A change from 700 F to 710 F degrees is not just a 10 F change but a infinite number of smaller fractions of that 10 F.

4. Analog to Digital Converter
Analog Input Signals
Analog Input Interface:Translates the continuous analog input signals into discrete values with in the PLC. (analog to digital converter) S T
Analog
input interface
Continuous Signal
PLC
Word/Bit file
of Memory
Analog to Digital Converter

5. Analog Input Devices Flow Transducers Humidity Transducers
Load Cell Transducers
Potentiometers
Pressure Transducers
Vibration Transducers
Temperature Transducers

6. Analog input Signal ratings
Voltage Range
10V dc
0 to 10V dc
0 to 5V dc
1 to 5V dc
Current Range
20 mA
0 to 20 mA
4 to 20 mA
Unipolar: Positive voltage only
Bipolar: Positive and Negative

7. Digital to analog converter
Analog Output signals
Analog Output Interface:Translates the discrete values of the PLC into continuous analog output signals. (digital to analog converter)
Analog
Output Interface
Continuous Signal
(voltage or current) S T
PLC
Word/Bit file of
Memory
Digital to analog converter

8. Analog Output Field Devices
Analog Valves
Actuators
Chart Recorders
Motor Drives
Analog Meters
Pressure Transducers

9. Analog output Signal ratings
Current Range
0 to 21 mA
0 to 20 mA
4 to 20 mA
Voltage Range
10V dc
0 to 10V dc
0 to 5V dc
1 to 5V dc
Unipolar: Positive voltage only
Bipolar: Positive and Negative

10. Resolution Resolution:The smallest detectable increment of measurement
This is a reference to the accuracy of the A/D converter.
15bit = Signal/32767 (0 to steps)
14bit = Signal/16384 (0 to steps)
13bit = Signal/ 8192 (0 to 8193 steps)
12bit = Signal/4096 (0 to 4095 steps)
Example: 12 bit resolution with +10 volt signal.
10Vdc/4095 = 2.4mV per step
Example: 15 bit resolution with +10 volt signal
10Vdc/32766 = 305uV per step

11. Resolution
Calculating number of counts per unit. Using a temperature range of 00 to To determine the counts per degree with 12 bit resolution.
Example: Total Counts / Total Degrees = Counts Per Degree
4095/100 = 4.095
Example: Counts Per Degree x Units per step = Units per Degree
4.095 x 2.4mV = 9.8mV

12. Single ended: All analog channels share the same common
Input/Output Wiring
Single ended: All analog channels share the same common 1 2 3 4 5 6 7
COM
Analog device
Terminal
Block
Channel 1
Channel 2 1 2 3 4
P L C 5 6 7 8 9 10

13. Differential: All analog channels have individual commons
Input/Output Wiring
Differential: All analog channels have individual commons 1
COM 2 3 4
Analog device
Channel 1
Channel 2
Terminal
Block

14. Field Devices
Transducer: Converts the field device variable (pressure, temp)
into a very low electrical signal. (current or voltage)
Transmitter
Channel 1
Transducer
Process 1
COM 2
Senses
physical
signal
COM
Low Level signal
current/voltage 3
Amplified signal
compatible with
analog interface
COM 4
Transmitter: Amplifies the signal to an interface rated signal (4-20mA, 0-10v)
COM

15. Analog Target Customers
Vertical markets:
SCADA Industry (New installations and existing A-B installations)
Water/Waste Water
Oil & Gas
Electric Power
Process Industry
Food Industry
General Industry machinery applications