Figure 4-11. Analog Output Wiring (on CPU Module)
4.9 Discrete Inputs (DI)
The discrete input (DI) monitors the status of relays, open collector/open
drain type solid-state switches, and other two-state devices. Discrete
inputs come from relays, switches, and other devices, which generate an
on/off, open/close, or high/low signal.
The DI provides a source voltage for dry relay contacts or for an open-
collector solid-state switch.
Each DI channel can be software-configured to function as:
Standard discrete inputs.
Latched discrete inputs.
A latched DI remains in the active state until reset. Other parameters can
invert the field signal and gather statistical information on the number of
transitions and the time accumulated in the on- or off-state.
The DI senses the low voltage (less than 0.5 V dc), which signals the
FB107 electronics that the relay contacts have closed. The opening of the
contacts allows the voltage to rise and the DI signals the FB107
electronics that the relay contacts have opened. An FB107 can read a DI a
maximum of 20 times per second (50 millisecond scan).
When a field device (such as a relay contact or open collector) is
connected across + and GND, the closing of the contacts completes the
circuit This activates current flow that the DI circuitry senses and, in turn,
signals the FB107 electronics indicating that the relay contacts have
closed.
To Next Page
Loading...
Need help?
General
