2.8 RS-232 interface connection
The digital interface RS-232 is designed for connection of various devices that transmit and receive information on
this interface, for example, FLS, CAN bus adapter, tachographs, RFID, MODBUS devices, etc.
The RS232TX interface line (pin 13) of the device should be connected to the RS-232RX line of the sensor, and the
RS232RX line (pin 14) to the RS-232TX.
14
7
13
6
12
5
11
4
10
3
9
8
2
1
«+»
«-»
Car battery
Fuse
(1A)
«GND»
Devices
Rx
Devices
Tx
FLS
Sensors Rx
Sensors Tx
RS232
Figure 39. Connection diagram of fuel level sensor by RS-232 interface
Periodic data output mode must be enabled in the sensor and the network address and data transfer rate must coincide
with those which are programmed in the device itself.
Note:
Some manufacturers of additional devices (FLS, CAN bus adapters, etc.) connected by the RS-232 interface change
the physical meaning of the designations of the TX and RX interface lines. That is why in this connection these devices do
not function, and it is required to reconnect them by swapping the RX and TX contacts.
If there is any doubt which sensor line is Tx and which Rx , it is possible check this with a multimeter in the voltage
measurement mode. The measured voltage on the sensor Tx line which is not connected to the terminal will be in the
range from -5 to -12 V relative to the sensor supply “-”. On the Rx line, the voltage will be close to “0”.
2.9 RS-485 interface connection
The digital interface RS-485 is designed to connect devices transmitting and receiving information via this interface,
for example, fuel level sensors, CAN bus adapter, tachographs, RFID, MODBUS-devices, etc.
As a rule, the interface is used to connect up to 16 digital fuel sensors. It is supposed to use digital LLS-compatible
sensors.
The RS-485 + interface line of the device should be connected to the RS-485 + line of the sensor, usually designated
as "A", and the RS-485 line of the device should be connected to the RS-485 line of the sensor, usually designated as "B".
The RS-485 interface specifications practically do not limit the length of cables on a land vehicle (100m or more), since the
interface is a differential bus and is well protected from the influence of external interference.
Summary of Contents for SMART S-2433
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