Brochure/Catalogue

Technical data
Common Mode Noise Elimination
• Generally, signals emitted by sensors have low levels
and are thus susceptible to capacitive and inductive
interference, such as those generated by motors,
frequency changers and other change processes.
This noise contents the measuring value and frequently
destroys expensive analog I/O cards in the control
electronics. Through the utilisation of analogue signal
isolators this interferace, which usually actions both
signal lines in common mode (push push), is effectively
eliminated through the zero potential input.
Active Isolator / Passive Isolator
• Active isolators draw their power supply from a separate
supply terminal to ensure that they can operate perfectly.
Depending upon the applications the input, output and
additionally the power supply are isolated from each
other. Only one supply is required for 3-port isolation.
However, it is isolated from the input and output circuits.
Thus even in the event of a short circuit, surge voltage
or reverse polarity, the downstream control electronics
cannot be damaged. Isolating the signals between the
input and output can be conducted either optically or
by transformer barrier depending upon the transfer rate.
Active isolators are non interacting, i.e. a change in the
load does not exert any inuence on an input circuit.
•
Passive isolators generate the current required for the supply
from the measuring signal. The current required internally is
so small that transfer problems do not occur here
.
• The feed can be effected from either the input or the
output side. Isolation is by transformer barrier. The advan-
tages are: cessation of network inuences, outstanding
accuracy, low signal delay and low potential requirement.
Passive isolators are not non interacting; a change in load
in the output circuit will inuence the input circuit.
Ground Loops
• The voltage supply‘s secondary side is earthed for the
purpose of setting up fast and secure ground loop
monitoring. If an analogue signal is fed in from a separate
voltage supply or if the sensing device itself is earthed,
then transient currents will ow between the ground
potentials across the interconnected ground connectors,
which in turn corrupts the measuring signal.
Analogue signal isolating ampliers prevent this form of
measuring signal corruption and inuence.
2-port Isolation
• The simplest form of analogue signal isolator is that of
2-port isolation. It serves to isolate the input circuit from
the output circuit as well as the two auxiliary voltages from
each other. Depending upon the isolator design and the
observed isolation data one refers here to base isolation
(galvanic isolation) or safe separation. ①
For current signals, 4...20 mA input current loop fed
modules are available. An additional auxiliary voltage for
the input circuit is not required here. ②
By connecting the input and output side voltage supplies,
the 2-port isolation can be converted to operate as a
simple signal converter. This is of particular interest where
isolation is not required for an application, but a signal
conversion has to be performed.
①
②
Technical data
W
Technical appendix/Glossary
W.6 2729490000