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.
The
second
action of the system is to react to the increased temperature in the
channel as a result of the overvoltage. 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 input range 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 higher local temperature, which starts the auto ranging
process. The system automatically increases the input range for as many times
as it requires to reach a 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.
Restore range selected by user automatically
As the GEN series system is designed to measure 24 hours a day, 7 days a
week, the automatic range switching has the negative side effect of reducing
the sensitivity of the amplifier. During the actual overload, the channel is unable
to measure the input signal. Therefore, there are no extra negative side effects.
If the overload disappears and the system runs unattended, the input range that
is selected automatically will not be the best measurement range. Therefore,
the amplifier "remembers" the range that the user originally selected and
restores this range as soon as regular thermal conditions are restored. A
temporary large overload will then only result in input sensitivity that is adjusted
temporarily.
The automatic range adaptation is started due to thermal conditions typically
as a result channel input overload. Therefore, the overload might still be
present. If this is the case the automatic range restore restarts, the thermal
increase and leads to re
-
trigger the automatic range adaption process and the
overload is handled exactly the same way as before.
The
third
action of the system takes effect if the second action is unsuccessful
and the local temperature remains outside of the maximum operating limits.
The input signal is disconnected from the channel. Grounding the input
disconnects the input signal from the external signal source. When inputs are
grounded, the only connections to the external signal are the input connectors
and the ground relay's input pin.
GEN3t
I3995-3.1 en HBM: public
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