“Field Apparatus having energy storing orgenerating characteristics of <1.2V, 0.1A, 25 mW or 25 microJ shall beconsidered Simple Apparatus (nonenergy storing). These general-purpose devicesmay be used in a hazardous (classified) location without further approval whenconnected to a certified intrinsically safe circuit.” - Quote from R. Stahl,Inc. Comprehensive Product Manual on Intrinsic Safety Barrier and RepeaterRelays.
Examples of non-energy storingIntrinsically Safe Apparatus are:
• Thermocouples, RTD’s, LED’s
• Dry Switch Contacts
• NAMUR Inductive Proximity Switches
• Non-inductive Strain Gauge Devices andResistors
The IRt/c falls into the category ofthermocouples, since it generates its signal by converting the radiated heatenergy to an electrical signal via Seebeck effects, the basic driving force ofthermocouples. Like all thermocouples, it requires no power source andgenerates signals measured in millivolts of voltage, microamps of current andnanowatts of power. IRt/cs have a small capacitance, but at one microfarad, theenergy storage is measured in nanojoules and is a thousand times lower than the25 microjoule criterion.
Accordingly, the IRt/c qualifies as aSimple Apparatus for use in hazardous locations, and with the appropriatebarrier, qualifies as Intrinsically Safe.