Industrial sensors are often called upon to be used in so-called “hazardous locations”. A hazardous area is one where flammable gases and/or dusts are either present, or could potentially be present.
Typically, sensors used in such areas must be specifically approved and certified for use in these areas in order to prevent accidental ignition of any flammable gases or dusts that may be present. The two most common protection methods are referred to as 1) explosion proof, and 2) intrinsically safe.
Contrary to popular belief, electrical equipment rated as explosion-proof, or ex-proof, is not designed to withstand an explosion. Rather, ex-proof equipment is designed so as to contain an internal explosion resulting from flammable gases or dusts entering the housing. This ability to contain an internal explosion prevents subsequent ignition of the surrounding atmosphere.
Electrical equipment classified as intrinsically safe, or “I.S.”, is designed such that there is not sufficient electrical energy present to cause flammable gases or dust to ignite. In many cases, intrinsically safe sensors employ so-called “barriers” that reside outside of the hazardous area and serve to limit the amount of energy available to the sensor.
Which Method is Better?
Neither protection method is inherently better than the other. They simply represent two ways to accomplish the same thing.