Yokogawa EJX115A - Manual (Page 7)

<2. Connection>
2-1
IM 01C25T03-01E
2. Connection
The BRAIN communication signal is superimposed
onto the 4 to 20 mA DC analog signal. Since
the modulated wave is a communication signal,
superimposing it on the normal signal will,
from basic principles, cause no error in the DC
component of the analog signal. Thus, monitoring
can be performed via the BT200 while the
transmitter is on-line.
2.1 Connecting the BT200
Connection to the transmitter with the BT200
can be made by either connecting to the BT200
connection hooks in the transmitter terminal box or
by connecting to a relaying terminal or a terminal
board.
Relaying
terminals
Distributor
Control room
Terminal board
F0201.ai
SUPPL Y
PULSE
CHECK ALARM
Figure 2.1 Connecting the BT200
2.2 Communication Line
Requirements
DPharp
BT200
Cable
resistance Rc
Cable resistance Rc
Load
resistance R
cc
Power
supply
● Loop resistance = R + 2Rc
= 250 to 600 Ω
● Loop capacitance = 0.22 µF max.
F0202.ai
Figure 2.2 Communication Line Requirements
2.3 Power Supply Voltage and
Load Resistance
When configuring the loop, make sure that the
external load resistance is within the range in the
figure below.
(Note) With an intrinsically safe transmitter, external load
resistance includes safety barrier resistance.
600
250
0 10.5 16.6 25.2 42
External
load
resistance
R (Ω)
Power supply voltage E (V DC)
F0203.ai
Communication
applicable range
R= E–10.5
0.0244
Figure 2.3 Relationship between Power Supply
Voltage and External Load Resistance