GE 8101-HI-TX 8-channel AI, 4-20mA with HART
always set on the ‘inner’ side of the alarm limitto be, typically, greater than the system noise
in the plant. If an alarm is activated, it will
remain until the input moves the full extent of
the deadband towards a “safer” value.
The Hi-Hi and Lo-Lo alarms support the
NAMUR recommendations, i.e. if the alarm
limit is set less than 3.6 mA (Lo-Lo), or greater
than 21.0 mA (Hi-Hi), the alarms must be
active for 4 seconds before the alarm is set.
The Deadband does not apply to NAMUR
alarms. If the alarm limits are set at values
between the NAMUR limits, the alarms function normally.
Dead zone
Each channel has a definable “dead zone”.
This is to reduce the need for the module to
report every minor change in input value. If
the input value differs by the amount defined
by the Dead Zone, or more, then the new
value is reported, otherwise it is not. This
reduces traffic on the internal bus which
improves the system response time. If the
Dead Zone value is set to zero (the default),
then every input value read cycle will set a
‘New Data’ flag, and be reported.
MODULE OPERATING STATES
Normal/Failsafe mode
The AI modules support failsafe mode as
defined in the earlier I/O module introductory section. When not in failsafe the module
adopts Normal mode.
Channel Active/Inactive
A channel can be made active or inactive
individually. When a channel is made inactive
inputs will not be processed.

Default/Power-up conditions
These modules use the following values when
they power up.
Module mode
Normal (not “failsafe”)
Active/inactive
All channels power up in the active state.
Alarms
All alarms are made inactive by having their
values set to high or low extremes, as appropriate.
Dead Zone
0 (i.e. all changes of A/D data are reported for
an active channel)
Software Filtering
Disabled.
Passthrough
Passthrough messages to HART instruments
are always allowed.
Visual indicators
CHANNEL “STATUS” LED (YELLOW)
On Sensor loop OK
Off Open circuit sensor and channel inactive
Flashing Open circuit sensor and channel active
OR Error condition
An error – i.e. a flashing LED – could be as a result of
any of the following conditions:
a) a loss of HART signal,
b) an error in the A/D converter,
c) a NAMUR alarm or
d) a Hi (-Hi) or Low (-Low) alarm.
GENERAL
These modules provide digitised data and
status information of analog measurements
from thermocouples, mV sources, RTDs and
resistance sources.
Thermocouple modules provide four or eight
channels for monitoring input signals from
thermocouples or mV sources. The function
of the module is set up during configuration.
Cold junction compensation for thermo couple applications is provided by means of
a sensor in the field terminal. Only the recom mended field terminals can be used with
these modules.
RTD modules provide four or eight chan nels for monitoring input signals from RTD
or resistance sources. The function of the
module is set up during configuration. The
RTD can be 2-, 3- or 4-wire type. Only the
recommended field terminals can be used
with these modules.