GE 8119-VI-05 8-channel Voltage Input, 1-5Vdc
Input sampling
Thermocouple modules sample at intervals of
60 ms per channel. In addition, the module has
cold junction temperature compensation that
is refreshed every 1.8 seconds for 4-channel
modules and every 2.4 seconds for 8-channel
modules. The sampling technique for the
RTD module is similar where samples of the
voltage across, and the current through, the
RTD are measured at intervals of 60 ms per
channel. Compensation methods reject the
effect of resistance in the cable conductors for
3-wire and 4-wire RTD/Resistance.
Data format
The 8105/6 and 8132 modules store data as
15-bit plus sign integers (–32768 to +32768).
The 8205/6 modules store data as 16-bit
unsigned integers (0 to 65535).
Filtering
An Infinite Impulse Response (IIR) filter is
used on the input data before it reaches the
A/D converter. Depending upon the coef ficients selected, the output from the filter
will be:
a) the input value (filter OFF)
b) an average of the last two readings (filter
ON - setting 1)
c) a running average of readings
(filter ON - setting 2)
The coefficients can be selected individually
for each channel.
Input alarms
Four configurable alarm levels are provided
for each channel—two high and two low (see
figure below). When an input value exceeds an
alarm limit a flag is set and the BIM gets
a new alarm status.
Alarm deadband
The alarm deadband (not shown on the
diagram) is fixed at 1%

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 will set a ‘New Data’ flag, and be
reported.
Open sensor detection
When configured to do so, the modules will
detect an open circuit sensor and report it
within 10 seconds. When this occurs a status
bit is set in the module and the affected
channel LED flashes. The detection options
for the two module types are configurable
as follows:
THC and mV
Off, drive upscale or drive downscale
RTD and resistance
Off or drive upscale
These choices can be made for each channel.
MODULE OPERATING STATES
Normal/Failsafe mode
The THC and RTD 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.