Rockwell Automation T80004 Application Note Field Loop Configuration - Manual (Page 39)

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AN-T80004 Field Loop Configuration
Issue 10 Jun 13 AN-T80004 39
Output energised (state 4)
This state occurs with a load fitted when the current demand is zero or positive and is thus the
expected state of a healthy output.
Current demand cannot be met (state 6)
(There is no short circuit state 5 for analogue current outputs; the channel will drive a short circuit with
the required current).
This occurs when the required current exceeds the capabilities of the channel.
Channel fault (state 7)
This is a module fault and operates in the same way as digital outputs.
Termination
Termination for system powered analogue outputs is very similar to digital outputs; the schematic
diagram above is identical. The T8842 VFTA and the T8850 FTA may be used as described for digital
outputs. There is no need to add termination resistors to outputs, indeed this will cause errors in the
loop current. Unused outputs may be wired to zero volts directly to satisfy diagnostics.
If using the T8850 FTA and I/O cables with power connection at the chassis end, the T8297 power
distribution unit should be used to connect field power. Wire the A and B supplies to pins 1 and 2 of the
central terminal block TB1; this connects the supplies together after passing through the 6A diodes on
the unit. The zero volt connections must be taken to the supply return separately so that the module
can measure the supply voltage.
Hazardous area outputs
The T8480 analogue outputs are not intrinsically safe or non-incendive. Separate power-limiting
devices should be fitted to satisfy the regulations in force. For EEx ‘d’ devices, mounted in sealed
explosion-proof housings, direct connection is allowed because the device housing provides the
protection.
Output
module
Field Supply
Load
for reference only