Appendix 2 Electrical Parameters - Labkotec SET-1000 12 VDC Installation And Operating Instructions Manual

SET-1000 12 VDC
Installation and Operating Instructions

Appendix 2 Electrical parameters

Example: Determing the maximum cable length
Influence of resistance Estimate for additional resistances in the circuit is 10 Ω. The max length of the
Influence of inductance Total inductance is 0,8 km x 3 μH/m = 2,4 mH. The sum value of the cable and
Influence of capacitance Cable capacitance is 0,8 km x 70 nF/km = 56 nF. Combined value of the cable
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When installing the device, make sure that the electrical values of the cable
between SET-1000 and sensor never exceed maximum electrical parameters.
The cabling between SET-1000 control unit and cable extension junction box /
cable joint must be executed as in figure 4 / 8 Extension cable should be
shielded paired twisted instrument cable.
Due to non-linear characteristics of the sensor voltage, the interaction of both,
capacitance and inductance, must be taken into account. The table below
indicates the connecting values in explosion groups IIC and IIB.
In explosion group IIA the values of the group IIB can be followed.
U = 14,7 V I = 55 mA
o o
The characteristics of the output voltage is trapezoidal.
Max. permissible value
Co
II C 608nF
3,84μF
II B
= 116,5 H/ (IIC) and 466 H/ (IIB)
L /R
o o
Table 2.Electrical parameters
Maximum length of the sensor cable is determined by the resistance (max. 75
Ω) and other electrical parameters (Co, Lo and Lo/Ro) of the sensor circuit.
Instrument cable with following characteristics is used:
- DC resistance of a twin wire at + 20°C is approx. 81 Ω / km.
- Inductance is approx. 3 μH / m.
- Capacitance is approx. 70 nF/km
cable is then (75 Ω - 10 Ω) / (81 Ω / km) = 800 m.
The influence of inductance and capacitance of a 800 m cable is:
e.g. SET/OS2 sensor [Li = 30 μH] is 2,43 mH. L/R ratio is thus 2,4 mH / (75 – 10)
Ω = 37 μH/Ω, which is less than the maximum allowed value 116,5 μH/Ω.
and the e.g. SET/OS2 sensor [Ci = 3 nF] is 59 nF.
When compared to the values in table 2, we can summarize that above values do
not limit the use of this particular 800 m cable in explosion groups IIB or IIC.
Feasibility of other cable types and sensors for different distances can be
calculated accordingly.
13/14
R = 404 Ω
P = 297 mW
o
Both Co and Lo
Lo Co Lo
568nF 0,15 mH
458 nF 0,5 mH
10 mH 388 nF 1,0 mH
328 nF 2,0 mH
258 nF 5,0 mH
3,5 µF 0,15 mH
3,1 µF 0,5 mH
30 mH 2,4 µF 1,0 mH
1,9 µF 2,0 mH
1,6 µF 5,0 mH
We reserve the right for changes without notice
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