Rockwell Automation T80004 Application Note Field Loop Configuration - Manual (Page 29)

Trusted
TM
AN-T80004 Field Loop Configuration
Issue 10 Jun 13 AN-T80004 29
Output energised/on (state 4)
This occurs when the channel output current is above the no-load threshold and below the short circuit
limit, an adequate field supply voltage is present and the voltage is above the Off threshold. This
proves that the output is energising the load and the load is within the module’s specification.
Short circuit in field wiring or load (state 5)
This is detected by separate logic that monitors the output current. The logic acts to allow excess
current as far as the circuit can stand. Nominal continuous ratings are 2A for T8451, 0.75A for T8461
and 0.5A for T8471.
Field fault (state 6)
This occurs when a de-energised output has an adequate field supply voltage, the measured current is
below the no-load threshold and the voltage is above the high On threshold or between the low On
threshold and the Off threshold, which implies it is externally biased to a voltage (e.g. supply voltage).
This will occur with hardwired matrix lamp tests on outputs driven from Trusted modules.
Channel fault (state 7+)
This state, and any number up to 15, indicates that the module is faulty. When the system considers a
channel faulty on a slice, the state is set to 15. The top bit indicates a module fault. The STATE
variable can be collected in the digital SOE buffer but only the lower three bits are recorded, so it will
appear as a 7 over SOE.
For clarity, the effect of the voltage thresholds is shown here as a graph.
Channel
Voltage
Field
Supply
High On Threshold
Low On Threshold
Zero Volts
Off Threshold
M
in
im
u
m
F
ie
ld
S
u
p
p
ly
V
o
lt
a
g
e
State 1
State 3 if output off and supply V OK
and current < no-load
State 6 if output off and supply V OK and current < no-load
State 6 if output off
and supply V OK
and current < no-load
State 2 if supply V OK
State 4 if supply V OK
and current > no-load
V
o
lt
s