Internal Wetted Contact Inputs; Internal Wetted Contact With Line Monitoring Wire Detection - GE Mark VIeS System Manual

Attention

7.10.3 Internal Wetted Contact Inputs

The switch is connected between PWR_RET and IO+, where the channel's DAC output is passed via the external switch
circuit to IO+ into the burden resistor. There are two types of external switch circuits supported as follows:
• Simple switch only
• Line monitoring (open/short detection) with the switch having two resistors in parallel and series
For the simple switch, the channel DAC is set for the contact current to flow from PWR_RET through the switch to IO+ into
the 250 ohm burden resistor to ground. The decision on switch state is based on current above or below 50% the set value as
measured on the burden resistor.
For line monitoring with detection of an open connection compared to an open switch, the DAC is set in voltage output mode
by firmware. The user adds two resistors to limit the current in normal operation with both set at the same value based on the
choice of desired current through the contact.
Internal Wetted Contact with Line Monitoring (Open/Short) Wire Detection
The variations on internal fed switches have the following contact voltages and currents.
Line Monitoring
Contact current
Resistor values (equal, 1% tolerance)
I/O+ for contact closed
Open Contact voltage
I/O+ for contact open
Threshold volts at IO+ for open loop
Threshold volts at IO+ for contact decision
Threshold volts at IO+ for short
198 GEH-6855_Vol_II
This mode of input uses low currents due to the load resistance. If the user's contact
cannot support under 1 mA of current flow, use the YDIA/STCI combination with 2.5
or 10 mA current flow.
This mode of input cannot support a field supply higher than 30 V. If 48 V or 125 V
operation is desired, use the appropriate YDIA/STCI combination supporting that
supply level.
Internal Wetted Simple Contact
Disabled
10 mA
Set by channel DAC in current output mode
Up to 24V
GEH-6855_Vol_II Mark VIeS Functional Safety Systems Volume II
None
2.5V
0
None
1.25
None
Public Information
Enabled
10 mA
Set by resistors, DAC is set to 5V
240 ohm ¼ watt
2.55
1.64
1.71
0.86
2.13
3.78