User's Manual

SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R08 Objective Specification Design-in
Page 148 of 188
Series current limiters
The use of three series blocking diodes in circuits of Level of Protection ‘ia’ is permitted, however, other
semiconductors and controllable semiconductor devices shall be used as series current-limiting devices only in
Level of Protection ‘ib’ or ‘ic’ apparatus. However, for power limitation purposes, Level of Protection ‘ia’
apparatus may use series current limiters consisting of controllable and non-controllable semiconductor devices.
The use of semiconductors and controllable semiconductor devices as current-limiting devices for spark ignition
limitation is not permitted for Level of Protection ‘ia’ apparatus because of their possible use in areas in which a
continuous or frequent presence of an explosive atmosphere may coincide with the possibility of a brief transient
which could cause ignition. The maximum current that may be delivered may have a brief transient but will not
be taken as Io, because the compliance with the spark ignition test of the clause 10.1 of IEC 60079-11
standard [33] would have established the successful limitation of the energy in this transient.
Protection against polarity reversal
Protection against polarity reversal shall be provided within intrinsically safe apparatus to prevent invalidation of
the type of protection as a result of reversal of the polarity of supplies to that intrinsically safe apparatus or at
connections between cells of a battery where this could occur. For this purpose, single diode shall be acceptable.
Other considerations
All the recommendations reported in the section 2.14.1 must be considered for the implementation of the VCC
supply circuit on application integrating SARA-G350 ATEX modules intended for use in potentially explosive
atmospheres. Any specific applicable requirement for the VCC supply circuit design must be fulfilled according to
all the exact applicable standards for the apparatus.
Check the detailed requisites on the pertinent normatives for the application apparatus, as for example
the IEC 60079-0 [32], IEC 60079-11 [33], IEC 60079-26 [34] standards.
2.14.3 Guidelines for antenna RF interface design
The RF output power of the SARA-G350 ATEX modules transmitter is compliant to all the applicable 3GPP / ETSI
standards, with a maximum output of 2 W RF pulse power and 1.15 mJ RF pulse energy in 850/900 MHz bands
and with a maximum output of 1 W RF pulse power and 0.58 mJ RF pulse energy in the 1800/1900 MHz bands
according to the GSM/GPRS power classes stated in Table 3.
The RF threshold power of the application device integrating a SARA-G350 ATEX module is defined, according
to the IEC 60079-0 ATEX standard [32], as the product of the effective output power of the transmitter (the
SARA-G350 ATEX module) multiplied by the antenna gain (implemented/used on the application device).
The RF threshold power of the application device integrating a SARA-G350 ATEX module transmitter, according
to the IEC 60079-0 ATEX standard [32], must not exceed the limits shown in Table 49.
Gas group II subdivision
RF threshold power limits according to the IEC 60079-0 ATEX standard
IIA (a typical gas is propane)
6.0 W
IIB (a typical gas is ethylene)
3.5 W
IIC (a typical gas is hydrogen)
2.0 W
Table 49: RF threshold power limits for the different gas group II subdivisions according to the IEC 60079-0 ATEX standard [32]
The system antenna(s) implemented/used on the application device for SARA-G350 ATEX modules must
be designed/selected so that the antenna gain (i.e. the combined transmission line, connector, cable losses
and radiating element gain) multiplied by the output power of the transmitter (SARA-G350 ATEX module)
does not exceed the limits shown in Table 49.