4. Intrinsic Safety Explosion Protection Instrumentation
4-13
TI 33Q01J30-01E
Considerations for Current Output Module
The current output module adjusts voltage so that it generates an appropriate value of current,
and outputs it. The output module checks if the value of output current and that of actual current
are the same. The current of 0 is considered as OOP. If the value of actual current is lower than
that of output current, Readback error occurs, which is considered as a hardware mdule failure.
Load
(Maximum voltage is 27.6 V)
When a burnout occurs,
the value of voltage is increased
to maximum, in order to increase
current.
Burnout!
Zener barrier
4-20 mA
Maximum working
voltage (Vwkg) 25.5 V
FIO input module
F040202.ai
Diode current
leakage
Current
output
Readback
check
As the voltage is more than 25.5 V,
Diode current leakage occurs.
- As the current is not 0, OOP
doesn't occur despite of burnout.
- As it is different from the value
that the actual current value should
indicate, it is considered as failure of module.
Figure Considerations for Output Module of Current
The voltage of more than 25.5 V produces Diode current leakage, so that the value of current
never becomes 0 in Readback check, despite of burnout. Therefore, the check of OOP is not
available. The value of current is considered as failure of module, because it is different from the
value of output current.
Apr. 25, 2022-00
