Interfaces
16
A05569_01_X00_00
HBM: public
AD105D
6
Interfaces
6.1
RS-485 2-wire interface
You can either connect a single transducer electronics module via the RS-485
interface or, by configuring a bus system, connect up to 32 transducer elec
tronics modules to
one
RS-485 interface. In this, all the electronics modules
are connected in parallel on one line. The total length of the line may be up to
500 m. The software uses the different addresses to differentiate between the
transducer electronics modules. If the control computer only has an RS-232 or
USB interface, an interface converter is required.
T/RA
T/RB
Control computer
Node 1
Node X
TxD
RxD
TB
TA
T
R
RB
RA
TxD
RxD
TB
TA
T
R
RB
RA
TxD
RxD
TB
TA
T
R
RB
RA
...
Fig. 6.1
Connection of several electronics to a PC via RS‐485
The interface signals T/RA and T/RB are switched in parallel for all AD105Ds
and the control computer. The transducer electronics already include the nec
essary bus termination resistors (termination resistor) that can be activated
with the
STR
software command. So no additional bus termination resistors
are needed on the electronics end. The ground reference for all of the interface
signals is based on the supply voltage ground (GND).
Address range
An address is necessary to be able to identify the nodes in the bus system un
ambiguously. The address may be between 0 and 89. The factory setting for
the address is 31. Set a different address with the
ADR
command.