Siemens SIMATIC S7-400 Reference Manual page 450

Glossary
A distinction is made between the process image of the inputs and the outputs. The process
image of the inputs (PII) is read from the input modules by the operating system prior to
execution of the user program. The process image of the outputs (PIQ) is transferred to the
output modules by the operating system on completion of program execution.
Product version
The product version distinguishes products with the same order number. The product version
is incremented when upwards-compatible functional enhancements are made, when there are
modifications relating solely to production (use of new components) and when bugs are fixed.
PROFIBUS DP
Digital, analog and intelligent modules, along with a wide range of field devices complying with
IEC 61784-1:2002 Ed1 CP 3/1, such as drives or valve clusters are moved away from the
automation system to the local process over distances of up to 23 km.
The modules and field devices are interconnected with the automation system over the
PROFIBUS DP Fieldbus and are addressed in the same way as centralized I/O.
Programming device
A programming device (PG) is a personal computer with a special compact design, suitable
for industrial conditions. A programming device is completely equipped for programming the
SIMATIC automation systems.
RC element
Connection of ohmic resistor and capacitor in series. When a consumer is turned off, an
overvoltage occurs in circuits with an inductive load that can cause an electric arc and can
reduce the life of the contacts. To extinguish this electric arc, the contact can be bridged by
an RC element.
Reaction time
The reaction time is the time from detecting an input signal to changing the output signal
associated with it.
The actual reaction time is between a longest and a shortest reaction time. When configuring
a plant, the longest reaction time must always be assumed.
Reference channel error
Parameter in STEP 7 for analog input modules. This parameter enables the error group
message of the reference junction when using thermoelements. A reference channel error
occurs when using thermoelements:
● When a fault occurs (for example broken wire) in a reference channel to which a
thermoresistor (RTD) is connected (channel 0) to compensate temperature drift.
● When the → reference temperature is outside the permitted range of values.
450
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08