Analog Output Modules
4-20mA Output Module IOP320
Metso Automation MAX Controls Inc. • 277596 •
6-3
S1 Setting W6 Setting W7 Setting Base Address
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
A
A
B
B
C
C
D
D
E
E
out
in
out
in
out
in
out
in
out
in
out
in
out
in
out
in
out
in
out
in
out
in
out
in
out
in
out
in
In
Out
In
Out
In
Out
In
Out
In
Out
In
Out
In
Out
In
Out
In
Out
In
Out
In
Out
In
Out
In
Out
In
Out
16
24
32
40
48
56
64
72
80
88
96
104
112
120
128
136
144
152
160
168
176
184
192
200
208
216
224
232
Module Operation
This microprocessor-based module supports up to eight 4-20 mA output
channels. Communication between the microcontroller and each output is
serial. The output request received from the I/O bus is translated by the
microcontroller into a pulse width modulated signal, which is transmitted to
each output circuit via a high-speed optical isolator. This optical isolator
provides the isolation between the logic and the field.
The duty cycle of the serialized output is proportional to the output level.
The output circuit converts this signal into 4-20 mA. Open load is detected
and reported to the DPU.
The FPGA provides the I/O bus interface logic; its program is loaded from
the FLASH on power up.
A watchdog timer function is included to monitor communications on the
I/O bus. The watchdog timers will timeout if there is no communications on
the I/O bus for longer than 0.7 seconds. When this occurs, the outputs will
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