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

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

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.

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 0000000000000000 Analog to Digital Converter

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

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

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 0000000000000000 Digital to analog converter

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

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

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 32766 steps) 14bit = Signal/16384 (0 to 16383 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

Resolution Calculating number of counts per unit. Using a temperature range of 00 to 1000. 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

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

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

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

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