IFM Electronic Ecomat Mobile Series System Manual page 289

Glossary of Terms
information),
- personal protective equipment (helmet,
protective goggles).
PWM
PWM = pulse width modulation
Via PWM a digital output (capability provided
by the device) can provide an almost analogue
voltage by means of regular fast pulses. The
PWM output signal is a pulsed signal between
GND and supply voltage.
Within a defined period (PWM frequency) the
mark-to-space ratio is varied. Depending on
the mark-to-space ratio, the connected load
determines the corresponding RMS current.
→ chapter PWM signal processing
(→ page 161)
→ chapter What does a PWM output do?
(→ page 179)
R
Ratio
Measurements can also be performed
ratiometrically. The input signal generates an
output signal which is in a defined ratio to the
input signal. This means that analogue input
signals can be evaluated without additional
reference voltage. A fluctuation of the supply
voltage has no influence on this measured
value.
→ Chapter Counter functions (→ page 200)
redundant
Redundancy is the presence of more than the
necessary means so that a function unit
performs a requested function or that data can
represent information.
Several kinds of redundancy are distinguished:
•
Functional redundancy aims at designing
safety-related systems in multiple ways in
parallel so that in the event of a failure of
one component the others ensure the task.
•
In addition it is tried to separate redundant
systems from each other with regard to
space. Thus the risk that they are affected
by a common interference is minimised.
•
Finally, components from different
manufacturers are sometimes used to
ifm System Manual ecomatmobile SmartController (CR2500) V05
avoid that a systematic fault causes all
redundant systems to fail (diverse
redundancy).
The software of redundant systems should
differ in the following aspects:
•
specification (different teams),
•
specification language,
•
programming (different teams),
•
programming language,
•
compiler.
remanent
Remanent data is protected against data loss
in case of power failure.
The operating system for example
automatically copies the remanent data to a
flash memory as soon as the voltage supply
falls below a critical value. If the voltage supply
is available again, the operating system loads
the remanent data back to the RAM memory.
The data in the RAM memory of a controller,
however, is volatile and normally lost in case of
power failure.
Reset, manual
The manual reset is an internal function within
the SRP/CS used to restore manually one or
more safety functions before re-starting a
machine.
Residual risk
Risk remaining after protective measures have
been taken. The residual risk has to be clearly
warned against in operating instructions and
on the machine.
Risk
Combination of the probability of occurrence of
harm and the severity of that harm.
Risk analysis
Combination of ...
•
the specification of the limits of the
machine (intended use, time limits),
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