Aplisens SGE-25.SMART Manual do utilizador - Página 7
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C
6. Supply examples
Power supply with a linear characteristic may be e.g. a typical barrier with parameters:
Uo=28V Io=0.093A Rw=300
Rw
Rw
Ui
Fig.1. Power supply from a source with linear characteristic"
Example of power supply from a source with trapezoidal characteristic (see Fig.2).
Uo=28V Io=0,08A
Ii
Ui
Fig. 2. Power supply from a source with trapezoidal characteristic"
If Uo < ½ Uq
For power supply with rectangular characteristic:
The supply of power from a source with a rectangular characteristic means that the voltage of the Ex power
supply remains constant until current limitation activates.
The protection level of power supplies with a "rectangular" characteristic is normally "ib".
The probe powered from such a supply is also a Ex device with protection level "ib".
Example of practical provision of power supply with a "rectangular" characteristic:
– use a stabilized power supply with o Uo=24V with protection level „ib" and current limited to Io=50mA.
6.1. The protection level
The probe is Ex device with protection level „ia" when the powered circuit have protection level „ia".
The probe is Ex device with protection level „ib" when the powered circuit have protection level „ib".
PROBE
Fig.3. SGE–25, SGE–25S, SGE–25C probes in Ex version – connection method
Devices in the measurement loop of the probe should be connected in accordance with
Intrinsic safety and explosion protection standards.
It is not permitted to repair or otherwise interfere with the probe's electrical circuits in any way.
Damage and possible repair may be assessed only by the manufacturer or another authorized
party
Ω
.
I
ID
Uo
Io
Rw
Uo
4Pi
then
Uq =
Io
Red
+
_
Black
Probe cable
5
Appendix Ex.04 (SGE–25, SGE–25S, SGE–25C)
D
Example of practical provision of power supply for case:
use the barrier with the parameters given above
I
D
Uq
Uo(Uq-Uo)
Uq
, Rw =
, Po =
Io
Hazardous area
Terminal box
Rw`
a Ex power supply
see p.5 and 6
DTR.SG...04
(ENG)
Safe area
+
_