
AD104-R2, AD104-R5
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ba_aed104_8_e.doc
Fig: 5.3.2:
Wiring of an AD104-R5 with an interface converter RS232/RS485
R
T
TB
RxD
TxD on/off
TB
TA
+5V
500
Ω
+5V
500
Ω
500
Ω
500
Ω
RB
RA
+5V
500
Ω
+5V
500
Ω
500
Ω
500
Ω
TA
RB RA
R
T
RxD
TxD on/off
TB
TA
RB RA
R
T
RxD
TxD on/off
TB
TA
RB RA
Master line
4 - wire
Computer=Master AED = Slave 00
Slave 31
. . .
Line
termination
Line
termination
Fig: 5.3.3:
Bus structure 4-wire bus (RS485)
The bus wiring is not to be allowed in star configuration. The leads of the slaves are not to be increased of 3m.
The best solution here: choin the main leads directly to the slaves.
The quiescent -signal level on the RS-485 master line results in the 4-wire mode at:
TB - TA > 0.35 V
(quiescent -signal level due to the AED terminating resistors)
RB - RA > 0.35 V
(quiescent -signal level due to the master terminating resistors)
Since the RS-485 is a differential bus interface, the quiescent-signal levels are also stated as a differential
voltage between the lines (and not related to ground). It must further be noted that this interface tolerates a
maximum common-mode range of +/-7V. If it is necessary, equipotential bonding should be established
between the bus subscribers through a separate line. The cable shield should not be used for this equipotential
bonding.
The shield of the master line is connected with the shield of the AED housing (not with the supply ground).
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