Emerson FB2100 - 3-4. Digital Output Characteristics

FB2100 Flow Computer Instruction Manual
D301783X012
November 2023
I/O Configuration and Wiring 71
Note
When using a digital output to drive an inductive load (such as a relay coil), place a
suppression diode across the load. This protects the DO from the reverse Electro-Motive
Force (EMF) spike generated when the inductive load is switched off.
When configured as digital outputs, the channels have the following characteristics:
Table 3-4. Digital Output Characteristics
Type
Number Supported
Characteristics
Digital Output
(DO)
1 (I/O option 1)
0 to 2 (I/O option 2) as follows:

1 or 2 non-isolated channels
on CPU board (DI/DO/PI 1 and
DI/DO/PI 2). Two always
present; you can configure
one, both, or neither as DOs.

DO is a low side switch that
sinks current to ground

Current rating of 500 mA (see
note below)

Maximum operating
frequency of 50 Hz

Pulse off/on time can be
configurable with a 31 ms
minimum on time and a 31 ms
minimum off time

Can be configured in software
with an output state for initial
power-up and in the case of a
CPU failure

Software configurable failure
mode of fail open, fail closed,
or hold last state

When a channel is configured
as a DO it cannot be used as a
DI or PI channel
Note
Digital outputs are rated to 500mA maximum. In a small number of applications,
however, the load on the DO could have an effect on the uncertainty of the analog inputs
and outputs. The typical increase in uncertainty is around 0.05% and only occurs when all
of the following are true:
 Either of the two analog channels in the base I/O is used as an AI (in voltage mode) or
as an AO and
 Either of the two digital channels in the base I/O is used as a DO and
 The total current load on these two DOs is greater than 300mA
 Analog inputs in current mode and the I/O channels in the expansion
I/O boards are
not affected.