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
Type
Digital Output
(DO)
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.
I/O Configuration and Wiring
3-4. Digital Output Characteristics
Number Supported
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.
FB2100 Flow Computer Instruction Manual
Characteristics
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
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