6
３－３．System composition
(1) Intrinsically safe system
1. The oxygen detector shall be used as following composition.
2. The safety retainer to be connected with oxygen detector shall have linear characteristics and be passed
the type approval as it is.
Also it shall satisfy the following conditions.
(1)
Rating of safety retainer
Max voltage of intrinsic-safety circuit: Below 28V
Max current of intrinsic-safety circuit: Below 600 mA
Max power of intrinsic- safety circuit: Below 0.75W
(2)
Performance division and group
Performance division: ia
Group : ⅡC
(3)
Relations between allowable inductance (Lo) and allowable capacitance (Co)
of intrinsic-safety circuit, and external wiring inductance (Lw) and capacitance(Cw)
of intrinsic-safety circuit.
Lo ≧ Li + Lw
Co ≧ C + Cw
(4)
When making wiring connection for intrinsic-safety circuit, take care not to induce
an electric current and voltage which will spoil the performance of intrinsically safe
by the electromagnetic induction or electrostatic induction to the intrinsic-safety
circuit.
WARNING
！
Detector
head
Ze
ne
r
ba
rr
ie
r
Indicator
/alarm
unit
Hazardous area
Non-hazardous area
CVVS1.25mm
2
・2C or equivalent (MAX600m)
Hazardous
area
Non-hazardous
area
Safety retainer
Oxygen detector
Ｌｉ≒ 0
Ｃｉ≒ 0
≒ 0 shows a negligible value
Ｌｉ
Ｃｉ
Ｌｏ
Ｃｏ
Ｌｗ
Ｃｗ
