Operating manual ВІСТ.418266.006-03 НЕ
45
APPENDIX D
RECCOMENDATIONS ON THE CHOICE OF CABLE TO CONNECT BDBG-09 DETECTING
UNIT TO DATA DISPLAY SYSTEM
To provide stable operation of the BDBG-09 detecting unit, and stable data communications
between the BDBG-09 detecting unit and the data display system, you should use the cable with the
following parameters:
- number of twisted pairs: not less than 2 (pairs not in use should be connected to minus of
power supply from the side, where power is supplied to the cable);
- conductor cross section: from 0.22 to 0.75 mm
2
;
- wave impedance: from 100 to 120 Ohm;
- collective screen: yes;
- screen material: foil + copper plaiting (if an individual metal shielding cover is applied, it is
possible to use a cable without additional screen of copper plaiting);
- outer diameter: from 6 to 12 mm (to preserve hermiticity of Hirschmann CA6LD connection);
- resistance to mechanical and climatic factors: depending on the use conditions;
- active resistance per unit length: depending on the cable length according to the formula (D.1)
(it is determined based on the necessity to provide supply voltage of the detecting unit within
tolerance limits at maximum useful current):
max
min
2
I
l
U
U
R
ci
rul
−
,
(D.1)
where
R
rul
- active resistance per unit length, Ohm/m;
U
ci
– voltage at cable input (not more than 13 V), V;
U
min
= 7 V – minimum permissible supply voltage of the BDBG-09 detecting unit according to
the OM;
I
max
= 0.03 А – maximum useful current of the BDBG-09 detecting unit according to the OM;
l
– cable length, m.
- unit-length capacitance: depending on the cable length according to the formula (D.2) (it is
determined based on the necessity to provide build-up time at transferring one data bit less than ¼
of all transference time of this bit):
2
4
1
l
R
s
C
rul
ulc
,
(D. 2)
where
С
ulc
- unit-length capacitance, F/m;
R
rul
- active resistance per unit length, Ohm/m;
S
– data exchange rate, 19200 bps;
l
– cable length, m.