OPW M2010-EU, Руководство по установке

Страница: 144 / 149

Capacitance of the field wiring from the intrinsically safe equipment to the Associated Apparatus shall be
calculated and must be included in the system calculations. Capacitance of the cable is Ccable. When
the cable capacitance per foot is not known, the following value shall be used: Ccable = 60pF/ft
The ISI, with or without sensor, has a Ci of OuF, so only the capacitance of the field wiring cable need to
be totaled and compared with the Associated Apparatus.
Total ISl(s) Ci + Ccable Associated Apparatus output parameters
Ci (s) + Ccable ≤ Ca, Co
5. Calculating Inductance
Inductance of the field wiring from the intrinsically safe equipment to the Associated Apparatus shall be
calculated and must be included in the system calculations. Inductance of the cable is Lcable. When the
cable inductance per foot is not known, the following value shall be used: Lcable 0.2uH/Ft.
Add the Li Inductance of all the Sensors connected to the network and the cable inductance and compare
it to the Associated Apparatus.
Total ISl(s) Li + Lcable Associated Apparatus output parameters
Li (s) + Lcable ≤ La, Lo
EXAMPLE:
1,000 ft cable 0.0002 * 1000 = 0.2mH
8 sensors Li = 0.165mH 0.165 * 8 = 1.32mH
8 sensors Li = 50uH 0.00005 * 8 = 0.0004mH
Total inductance in network 0.2mH + 1.32mH + .0004mH = 1.5204mH
6.
Connecting a third party sensor to standalone ISI
To determine the safe connection of the ISi stand alone to a third party approved sensor with entity
parameters the following considerations should be used.
The maximum cable length used to connect the ISI to the sensor shall be less than 15M. The Lo entity
parameter has already factored in the sensor / ISI connecting cable of 15M. maximum.
Doc. No.: M2010-EU Rev.: 13
Page 144 of 149