Rockwell Automation T80004 Application Note Field Loop Configuration - Manual (Page 12)

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AN-T80004 Field Loop Configuration
Issue 10 Jun 13 AN-T80004 12
For field powered devices, sourcing current, where the channel current could go below 4mA (e.g. gas
detector optics alarms):
Since the current loop is on the negative side of the channel power, it is possible to configure the
T8834 FTA to power and sense current-sinking devices, where the loop draws current away from the
channel. Current sinking devices need a separate power supply.
Product description PD-T8834 shows the full circuit diagram of a channel. The circuit includes links
which could be modified to accommodate other requirements.
Isolated PSU
+ -
TB1 A
TB1 B
100R
7V5
SUPPLY
REFERENCE
SIGNAL
TB2 +
TB3 +
TB2 -
TB3 -
4K75
Isolated PSU
+ -
TB1 A
TB1 B
100R
7V5
SUPPLY
REFERENCE
SIGNAL
TB2 +
TB3 +
TB2 -
TB3 -
4K75