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# 60079-11: Intrinsic Safety: I have 24V and 200mA, which is Pin=4.8W, what is P = Vo*Io / 4 equation

## 60079-11: Intrinsic Safety: I have 24V and 200mA, which is Pin=4.8W, what is P = Vo*Io / 4 equation

(OP)
I come across the equation P = Vo*Io / 4

(1) I have 24V and 200mA AC/DC PSU into Zone 2 sealed case (IP67) with electronics and barrier modules for sensors attached to pipes. This is 4.8W, but I come across a weird equation P = Uo * Io / 4, what are they?

(2) What kind of barrier to use between external AC/DC adaptor to the above box, how short the 110V main cable should be. It would be placed in the Zone 2 area (ie Dog House).

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