Siemens SIMATIC S7-400 Reference Manual page 448

Glossary
Measuring principle, instantaneous value encoding
A module with instantaneous value encoding is always used for extremely fast measurement
methods or for values that change very quickly. With this technique, the module accesses the
variable to be measured as quickly as possible and returns an instantaneous recording of the
signal at a specific time. It should be remembered that due to this measurement method, the
modules are more "sensitive" than the modules using the integrating method. As a result,
interference affecting the measured value can lead to falsification. When using these modules,
you should make sure that the measurement signal is "clean", for example by adhering to the
installation instructions.
Measuring principle, integrating
A module with an integrating measurement technique is always used for measurements that
are not time-critical. The integration time is inversely proportional to the network frequency.
You set the network frequency in STEP 7 and this results in the integration time. At a network
frequency of 50 Hz, the integration time is 20 ms or even multiples of 20 ms. Since the
measured value is integrated over exactly this period, at least one or more entire periods of
the network frequency that may be superimposed on the measurement signal are also
recorded. The mean value of the interference is therefore integrated to zero (positive
component of the first half period = negative component of the second half period) and, as a
result of the principle, only the useful signal is detected.
Measuring range module
Measuring range submodules are plugged onto analog input modules to adapt them to various
measuring ranges.
Memory reset
During a memory reset, the following memory areas of the CPU are erased: Work memory,
write/read area of the load memory, system memory.
The MPI parameters and the diagnostic buffer are retained.
Mode
Mode means the following:
1. The mode in which the CPU operates as set by the mode selector or using a PG
2. The type of program execution on the CPU
Mode selector
Using the mode selector, the user can set the current mode of the CPU (RUN, STOP) or reset
the memory of the CPU (MRES).
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S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08