Digital Output
The I/O channel can also be used as a discrete output. The digital output uses an field-effect transistor (FET) rated
at 30 Vdc 500 mA, and can be used to switch a load, such as a relay coil or contactor. The output can be activated
by manually writing a value of
“1” to register location 1 using the I/O Diagnostics page within the module’s Web
Server or using the on-board Modbus TCP server or serial Modbus master to turn on the output. It can also be
accessed from an external Modbus server (such as a PLC, DCS, or SCADA) via the Ethernet network or serial
interface. When the output is activated, the I/O indicator appears red.
NOTE The digital output operation will override the digital input operation. For example, if the output is
activated while the DIO is being read, the indication will show the input as being on (1).
Figure 19 DIO Output
Digital Input
When used as an input, the I/O channel supports a voltage-free contact connection such as a mechanical switch
or an NPN transistor device, such as an electronic proximity switch. Contact wetting current of the input is
approximately 5 mA, and is provided to maintain reliable operation for driving relays. The digital input is activated
by connecting between the
“IO” and “COM” terminals.
The I/O indicator on the front panel of the module appears green when the input is switched on (closed/shorted).
The device will be able to activate the digital input if the resistance of the switching device is less than 200 ohms.
NOTE PNP transistor devices are not compatible with this digital input.
Figure 20 DIO Input (Switch)
Figure 21 Digital Input (Transistor)
