Entity Parameters

The entity concept allows manufacturers to certify their devices as an isolated entity. An installer can take two such devices from different manufacturers and determine if they can be safely connected together. Without the entity concept the two devices would have to be certified as a system.

Consider the case of a zener barrier and a current transmitter which are to connected together.

The barrier will list the following parameters:

Voc = maximum voltage that can be present on the hazardous area side in the event of a fault

Isc = maximum current that can be present on the hazardous area side in the event of a fault

Co = maximum capacitance that can be connected to the barrier (including cable capacitance)

Lo = maximum inductance that can be connected to the barrier (including cable inductance)

The current transmitter will list the following parameters:

Vmax = maximum voltage that can be applied

Imax = maximum current that can be applied

Ca = maximum capacitance that can be connected to the hazardous area side

La = maximum inductance that can be connected to the hazardous area side

To test if a barrier and the current transmitter can be connected together safely the installer will check that:

Voc < Vmax , Isc < Imax , Ci < Ca and Li < La