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Is there a PCB guideline paper or book that discusses how to design PCB layout and components that meet IEC60079 (-0, -11, -7) and how to limits the use of encapsulation or conformal coating.

In my case, I have an off shelve certified Zener barrier module attached to 4-20mA sensor device (protected input). The unprotected signal/power from Zener Barrier is then attached to my DAQ PCB, it has current limiter build-in on 24V terminal which avoids overheating in event of shorting faults. My DAQ board has lot of 0402/0603 res/cap but avoided tant/elec cap. (An expert for initial review suggested this board with 0603/0402 and small IC along with tracking layout does not qualify in IEC60079-11, I'm unsure why or which clauses in that standard apply). The power consumption of the board is less than few watts and mostly 5V/3V3 with 24V to 4-20mA sensor.

The IEC60079-0 (clause 5.3) defines a component with surface area, do they also apply to PCB as a component with 11,000 mm2 surface area? or do they apply to discrete parts?

It says Max Pd = 1.3W for +40C ambient, do they apply only for discrete part or whole PCB as a component?

How thick conformal coating, how to decide on that?

The DAQ unit resides in Zone 2 (Group IIB, T4).

(Ref: PCB design for intrinsically safe equipment to 60079-11 standard)

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  • \$\begingroup\$ Draw a picture of the setup because, that is why EEs use circuit diagrams. \$\endgroup\$
    – Andy aka
    Jan 29, 2020 at 16:26
  • \$\begingroup\$ Intrinsic safety, and particularly ATEX, is extremely complex and highly application dependent. Different parts of your circuit may have different rules. The 1.3W, for example, is based on surface area. I know more about ATEX design than most engineers, but my current project still involves weekly consultations and daily emails with my UL rep. \$\endgroup\$ Jan 29, 2020 at 18:02
  • \$\begingroup\$ The surface area of a discrete component or PCB as the component, which is which? \$\endgroup\$
    – Riscy
    Jan 30, 2020 at 14:38

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