...
Current
...
Input Mode
Current Input
The FAC-2100
...
can
...
read
...
0/4mA
...
to
...
20mA
...
currents
...
on
...
any
...
of
...
its
...
analog
...
inputs.
...
An
...
analog
...
input
...
configured
...
in
...
software
...
for
...
current
...
mode
...
will
...
automatically
...
engage
...
a
...
250
...
ohm
...
resistor
...
(physically
...
located
...
in
...
the
...
controller)
...
from
...
the
...
A
...
IN+
...
pin
...
to
...
GND.
...
Typical Wiring Diagram
The figure below shows a typical hook-up
...
for
...
loop
...
powered
...
4-20mA
...
transmitters.
...
This
...
configuration
...
uses
...
the
...
internal
...
28V
...
axillary
...
voltage
...
source
...
to
...
power
...
the
...
transmitter.
...
Note
...
the
...
connection
...
from
...
the
...
analog
...
input
...
return
...
back
...
to
...
ground
...
of
...
the
...
voltage
...
source
...
is
...
made
...
internal
...
to
...
the
...
controller.
...
Also
...
note
...
that
...
the
...
A
...
IN-
...
pin
...
is
...
not
...
used
...
in
...
this
...
mode.
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Suggested Analog Input Wiring with a Loop Powered Transmitter
The figure below shows a 4-20mA sensor (not loop powered) connected to the controller where the sensor is powered by an external source. Note that a similar connection is made when using a 4-20mA loop sensor that is externally powered.
Suggested Analog Input Wiring with an Externally Powered 4-20mA Sensor
Over-Current Shutoff
When the input is in current mode the device will automatically protect itself from currents that exceeds approximately 25mA. When this condition is detected the circuitry will automatically disconnect the 250 ohm resistor and thereby open the circuit (this will also turn off an attached loop transmitter). A short time later the 250 ohm resistor will be reengaged to see if the fault has cleared. If not, the cycle will repeat.