Intrinsic Safety relies upon the equipment supplies being of low voltage and power and is suited to electronic devices. The operating current of the circuitry should be low enough not to be affected by series resistance, which may be required to limit energy.
The circuitry should contain low values of inductance and capacitance.
Supply values exceeding 30V and 1.3W are possible though increasingly more difficult to certify.
A detailed analysis of the circuit design will be undertaken. In short your circuit design will probably need to be modified to achieve certification, so this protection concept is not suited to circuit boards that cannot be modified.
The strength and shape of the enclosure is not so important as full control and knowledge of the circuit design.
ia for zone 0 and 20
ib for zone 1 and 21
ic for zone 2 and 22
Important Design Parameters
- Use of certain components for electrical and electronic circuits
- Lower permitted load on the components than in ordinary industrial applications with regard to:
- Voltage with regard to electric strength
- Current with regard to heat
Voltage and current, including a safety margin, are kept so low that no impermissible temperatures can occur. Sparks and arcing (in the event of open circuit or short-circuit), posses so little energy that they are unable to ignite a potentially explosive atmosphere.
An impression of this protection type is provided by the fact that potentially explosive atmospheres of subgroup IIA require only a few hundred μW and those of subgroup IIC only 10 μW for ignition.
- Instrumentation and control
- Sensors working on physical, chemical, or mechanical principles
- Actuators working on optical, acoustic, and, to a certain extent, mechanical principles