Hello all,

I'm currently working on a portable electronic device that needs to function in an area that has volatile gasses. I need a high safety factor on the inputs and outputs of the device. I do not want to start a fire from an ESD spark. I've looked into spark gaps but I would like to know if there was any other way of solving this problem.

Thanks

 

Intrinsically safe devices are limited in the voltages and currents that they can use, and there are different levels of intrinsic safety. The challenges of designing and certifying such products was too great for our company to undertake the development risk. Our insurance company said they would cancel our liability insurance if we went through with the project. The agent was as close to an MI as I have ever seen another human. We burned the proposal and the design documents; then we buried the ashes.

 

Spark gaps might not be your best bet since they usually operate a higher voltages (I include gas discharge tubes such as neon bulbs and regulators in the "spark gap class".

Metal Oxide Varistors (https://en.wikipedia.org/wiki/Varistor) are made to clamp at a variety of voltages and come in a variety of sizes to absorb various amounts of energy; their main drawback is they have relatively high capacitance, which affect signal quality. Zener diodes (https://en.wikipedia.org/wiki/Zener_diode) are a good choice for low currents and lower capacitance. Transient voltage protectors

Transient Voltage Suppressor diodes (https://en.wikipedia.org/wiki/Transient-voltage-suppression_diode) can be better for handling high frequency signals.

Those are the two traditional components used to protect against high voltage transients, such as ESD, though there are other more ways that are more tricky or complex that can be applied to specific applications.

If you can describe the voltages and signals involved, and the maximum voltage you are allowed (that would probably depend on the physical dimensions of your potential spark gap), you can probably get more targeted advice.

A more general list of possible sountions:
https://en.wikipedia.org/w/index.ph...transient+voltage+suppression&profile=default

 

I recall using, in LPG carriers and tankers, VHF handies (Standard was the brand) advertised as intrinsically safe for explosive atmospheres (?)

Peeking at the circuit maybe could give you an idea.

But, like with alarmas and so many critical designs, my doubt is: how do you actually test them? Mythbusters?

 

the talkies are intrinsicly safe due to the case design, not the circuit. the cases are designed to contain all sparks and explosions. completely sealed. another version of intrinsicly safe limits power available on inputs and outputs, real low power outputs means no sparks and no ignition.

 

IMO
The OP should contact a professional engineer with appropriate background.
This is a serious application and knowledge should NOT be gained from the internet on this one..

Either put the product back in the drawer as papabravo spoke of or seek professional design assistance and not via an internet forum.
Lives are at stake.

"But your honor... the people on the internet said it was ok"

 

Strap yourself to a resistive ground and touch a conductor on each device before you plug them together?
Raise the humidity in the area above 70% RH and work slowly?
No, those are external to what you're building.

I think you can't build a lack of environmental static electricity into a box of something.
Your question really puzzles me.

 

IMO
The OP should contact a professional engineer with appropriate background.
This is a serious application and knowledge should NOT be gained from the internet on this one..

Either put the product back in the drawer as papabravo spoke of or seek professional design assistance and not via an internet forum.
Lives are at stake.

"But your honor... the people on the internet said it was ok"

Listen to mcgyvr, this stuff is really really really not for the uninitiated. You could literally loose everything you have. Even if you prevail in court you will be bankrupt and penniless. It just isn't worth the heartburn. The moderators of this boead have taken strong positions on numerous topics and this might be even more dangerous than automotive modifications or LEDs to mains. I strongly urge this thread to be closed.