Thermal monitor of the input channels
Any overload results in extra heat being generated within the channel. The extra
heat is the result of the extra current flowing through the input resistance. The
extra heat is also caused by internal amplifier sections driving their local output
to maximum levels, which creates excessive heating within the amplifier.
As a third
protective mechanism, every input is equipped with a thermal sensor
to monitor the local temperature. When the local temperature reaches
maximum levels, the system automatically starts changing the input range that
has been selected by the user to reduce the dissipated heat. As the heat
dissipation does not start the auto ranging immediately, short overloads do not
result in auto ranging. A longer overload leads to a higher local temperature,
which starts the auto ranging process.
Whenever an overload pushes local temperature to exceed the maximum level,
the input range is adapted to a range that is less sensitive by a factor of ten.
For example, if the user has selected a range of
±
40 mV and it is necessary,
the system changes the range to
±
400 mV. As this might not be enough due
to an even higher overvoltage, the system keeps monitoring the local
temperature. If the local temperature is not reduced within the expected
response time, the system automatically increases the input range by a factor
of 10 for a second or third time or however many times it requires to reach safe
conditions that do not increase the local temperature anymore.
Every one of the automatic range changes is identified within the measurement
data. Not only is the measured input scaled with the adapted input range
correctly, but the exact moment when the automatic range change happens is
also identified within Perception software.
As the highest range that can be selected,
±
1 kV is the ultimate protection for
the system to disconnect the input from the external signal source. This step is
only executed if the system is in the
±
1 kV range and the local temperature is
still outside maximum operating limits. Disconnecting from the external signal
source is done by grounding the input. When inputs are grounded, the only
connections to the external signal are the input connectors and the input pin of
the ground relay.
GEN3i
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I3763-3.1 en HBM: public
