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Wiring of the level sensor for supplying purposes (in Ex, preferably blue cable) is by a dual-core
cable.. The cable cross-section is to be selected so that the supply voltage to the sensor is no less
than 10V in the borderline case of maximum current consumption (21.5mA) with a given cable
length L. A copper cable having a length of 100 m (100 m forward and 100 m return line) has a
resistivity of 3.4 Ω in a cable cross-section of 1mm
2
.
(R = 0,034 Ω x L (m)/F (mm
2
)). If a supplier
generates, for example, 13 V at 21.5 mA, the resistivity
R is allowed to be 3 V/0.0215 A = 139 Ω.
If the cable is of a cross-section of 0.5mm
2
, the feeder line is allowed to have a length L = R(Ω) x
F (mm
2
)/0,034 m = 20440 m.
Connecting Pattern for FFG-T...EX in an Area exposed to Danger of Explosion
FFG-T...EX (Ex-design) Separating Amplifier
Minimum Voltage: Umin
= 10 V + 0,0215 A x ∑R
∑R = Sum of all cable resistancess including feeder line and burden
Adjusting Measures
Measuring Range on the FFG-T...EX Sensor
Two keys and one illuminated diode (LED) in the connecting area of the probe head serve for
adjusting the 4 mA- and 20 mA-points on the FFG-T...EX system. The FFG-T...EX system is
adjusted, ex factory, to the maximum range from 4 mA on the probe base to 20 mA at the probe
head. The range of measurement for adaptation to the given container can be individually
adjusted; however, the distance must be no less than 5 mm. Otherwise the indication direction of
the sensor is automatically reversed.
For further details of adjusting the range of measurement reference is made to figure 6:
Unscrew lid (1) of probe head with open-end wrench
Keep 4mA-key (2) pressed for no less than 3 seconds.
The FFG-T...EX system now is in the a
djusting mode with the green LED (4)”Cal/Err” flashing. The
current consumption of the FFG-T...EX system is 12 mA. Without pressing the key again, the FFG-
T...EX system remains in the adjusting mode before changing back to the measuring mode without
modifying the adjustment.
auxiliary power
fig..5: connecting diagram of the FFG-T...EX
