Emerson ROC827 Discrete Input Modules, Representative Internal Circuit, Field Wiring

ROC827 Instruction Manual

Representative Internal Circuit

CURRENT LOOP

CONTROL

CURRENT LOOP

CONTROL

CURRENT LOOP

CONTROL

CURRENT LOOP

CONTROL

Field Wiring

I + CURRENT LOOP DEVICE 4-20mA

-ROC800 POWERED

+V	+
250	-	1-5 VOLT CONTROL DEVICE

DOC0505A

Figure 4-7. Analog Output Module Field Wiring

Note: All I/O modules are isolated on the field side. Be aware that you can induce ground loops by tying commons from various modules together.

4.5Discrete Input Modules

The eight-channel Discrete Input (DI) modules monitor 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 module provides a source voltage for dry relay contacts or for an open-collector solid-state switch.

The DI module’s LEDs light when each input is active.

Each DI channel can be software-configured to function as a momentary or latched DI. 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.

Caution	The Discrete Input module operates with non-powered discrete devices,
	such as “dry” relay contacts or isolated solid-state switches. Use of the DI
	module with powered devices may cause improper operation or damage.

The DI module senses the current flow, which signals the ROC827 electronics that the relay contacts have closed. The opening of the contacts interrupts the current flow and the DI module signals the ROC827 electronics that the relay contacts have opened. A ROC827 can read a DI a maximum of 20 times per second (50 millisecond scan).

Issued Mar-06 Input/Output Modules 4-9