User guide
    <2.  Connection>
2-3
IM 01C25R05-01EN
(6)  Connecting RS-485 USB Adaptor to EJX 
Multivariable Transmitter 
For conguration of EJX Multivariable Transmitter 
using DTM on PC, RS-485 USB Adaptor is required 
to connect transmitter to PC. Connecting RS-485 
USB Adaptor to EJX Multivariable Transmitter is 
described using BLACK BOX “SP390A-R2” isolated 
RS485 USB Adaptor as an example in Figure 2.3 
and Figure 2.4.
A
B
+
–
MODBUS
SUPPLY
BLACK BOX
TDA(-)
TDB(+)
RDA(-)
RDB(+)
GND
USB
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BLACK BOX 
“SP390A-R2” Isolated 
RS485 USB Adaptor
EJX Multivariable 
Transmitter
RDA(-) MODBUS A
RDB(+) MODBUS B
Figure 2.3  RS-485 USB Adaptor connection 
RS-485
Echo OFF
2 Wire
2 Wire
RS-422
Echo ON
4 Wire
4 Wire
1
2 3 4
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1 (RS422/RS485) RS-485
2 (Echo ON/OFF) Echo OFF
3 (4 Wire/ 2 Wire) 2 Wire
4 (4 Wire/ 2 Wire) 2 Wire
Figure 2.4  RS-485 USB Adaptor Setting 
IMPORTANT
Do not connect MODBUS(RS-485) wiring 
to Power terminals. It may damage RS-485 
adaptor.
NOTE
We recommend isolated RS485 USB Adaptor for 
connecting PC to EJX Multivariable Transmitter.
2.2  Integral Indicator Display 
When Powering On
For models with the integral indicator code “D”, the 
display shows all segments in the LCD and  
device/communication information sequentially.
All segments display 
Model name (3 s)
Communication Protocol (3 s)
Device Revision (3 s)
Slave Address (3 s)  Serial information (3 s)
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E.g.:
Baud rate: 9600 [bps]
Data Length: 8 [bit]
Parity: Even
Stop Bit: 1
NOTE
LCD display can be set to all segments display 
only.
• Procedure to call up the display 
[Root Menu] → Detailed setup → Display condition 
→ Chg power on info 
On
Show all segments display and 
device/communication information 
display when powering on.
Off
Show all segments display when 
powering on.










