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S5-115U Manual
A lithium battery backs up the program memory and the internal retentive flags, timers and
counters in the event of a power failure. An LED signals battery failure. If you change the battery
when the power is shut off, connect a back-up voltage from an outside source to the sockets
provided for this purpose on the power supply module.
1.2.2
Central Processing Units
The central processing unit (CPU) is the "brain" of the programmable controller. It executes the
control program. Choose from the following four CPUs, depending on the degree of performance
your S5-115U must have:
CPU 941, CPU 942, CPU 943 and CPU 944.
The more powerful the CPU you choose, the shorter are your program execution times and the
larger the user memory. You can use CPUs 941 to 944 also for PID control - in conjunction with
analog modules and PID control software - since the operating systems in these CPUs contain
integral PID control algorithms. Sampling times from 100 ms are possible for a PID control loop.
You can implement up to eight PID control loops.
CPU 943 and CPU 944 (each with two serial interfaces) offer further possibilities for controlling the
process thanks to their integral hardware clock.
1.2.3
Input and Output Modules
Input and output modules are the interfaces to the sensors and actuators of a machine or
controlled system.
The following features make S5-115U modules easy to handle:
•
fast installation
•
mechanical coding
•
large labeling areas
Digital Modules
Digital modules conform to the voltage and current levels of your machine. You do not have to
adapt the existing level to the programmable controller. The S5-115U adapts itself to your
machine.
Digital modules have the following convenient features:
•
connection of signal lines via front connectors
•
a choice of screw-type or crimp snap-in connections
Analog Modules
As a programmable controller's degree of performance increases, so does the significance of its
analog value processing. The significance of the analog input and output modules increases
accordingly.
Analog modules handle mainly closed-loop control tasks, such as automatic level, temperature, or
speed control.
EWA 4NEB 811 6130-02b
System Overview
1-3
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