5.5.2
Operation
The function and on-board signal conditioning are the same as those on TBCI. The threshold voltage is 50% of the excitation
voltage.
Contact input currents are resistance limited to 2.5 mA on the first 21 circuits, and 10 mA on circuits 22 through 24. The
combined contact excitation current is current limited to 0.5 A using polymer positive temperature coefficient fuses that can
be reset. Filters reduce high-frequency noise and suppress surge on each input near the point of signal entry. The discrete
input voltage signals go to the I/O pack, which passes them through optical isolators, converts them to digital signals, and
transfers them to the controller.
5.5.3
Specifications
Item
STCI Specification
Number of channels
24 dry contact voltage input channels
Excitation voltage
S2: Nominal 24 V dc, floating, 20 V dc min, 32 V dc max (Pluggable TB)
S4: Nominal 48 V dc, floating, 43 V dc min, 53 V dc max (Pluggable TB)
Input current
S2 (for 24 V dc applications):
First 21 circuits draw 2.5 mA
Last three circuits draw 10 mA
S4 (for 48 V dc applications):
First 21 circuits draw 2.5 mA
Last three circuits draw 10.4 mA
Input filter
Hardware filter, 4 ms
Fault detection in I/O board
Loss of contact input excitation voltage
Non-responding contact input in test mode
Unplugged cable or loss of communication with I/O board: contact status is displayed as False and
Unhealthy.
AC voltage rejection
S2: 12 V rms at 24 V dc excitation
S4: 24 V rms at 48 V dc excitation
Size
15.9 cm high x 10.2 cm wide (6.25 in x 4.0 in)
Technology
Surface-mount
5.5.4
Diagnostics
The I/O pack monitors the following functions on STCI:
•
The contact excitation voltage is monitored. If the excitation drops to below 40% of the nominal voltage, a diagnostic
alarm (fault) is set and latched.
•
YDIA performs periodic self-test of all contact inputs. In a alternative sequence each contact is forced open or close and
reads the status, if any contact fails the test a fault is created.
•
The terminal board connector has an ID device that is interrogated by the I/O pack. The connector ID is coded into a
read-only chip containing the board serial number, board type, and revision number. If a mismatch is encountered with
what is configured in the ToolboxST application, a hardware incompatibility fault is created.
YDIA Discrete Input Modules
GEH-6855_Vol_II System Guide 129
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