Question regarding ATEX compatible design (IEC60079-11)

[hm_fa_da]

Hi,

Recently I'm trying to design a device compatible with ATEX for Zone1,Ex ia, IIC.
i've seen in IEC60079-11 that electrolyte or tantalum caps shouldn't be used. but i see in two different I.S (intrinsically safe) products that they used tantalum caps on board ... !
1- How can those Caps be use

Thanks

 

[mpfisher]

IEC60079-11 mentions "blocking capacitors" which are used to block DC component of a signal usually on input or output of the device. It also mentions "filter capacitors" and according to the description there these caps are placed between the enclosure (frame) of the device and intrinsically safe circuit. These are usually used for EMI/EMC. Only for these types of usage electrolytic or tantalum caps should not be used as they may short-circuit leading to failure of I.S. circuit. I think you can use electrolytic/tantalum caps to filter power rails, etc.