Sensia 3300 EFM, Installation, Operation & Maintenance Manual

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Output Wiring
Analog (4 to 20 mA) Outputs
The 4 to 20 mA output ( Figure 3.15 ) provides a linear current output that can be configured to represent any parameter
in the holding registers using the Scanner 3300 web interface. This output requires a two-conductor cable connected to
a 9 to 30 VDC power supply (voltage required is dependent on loop resistance) and a current readout device located in
the remote location. The analog outputs are electrically isolated from each other and from the main electronics. See the
Scanner 3300 Web Interface User Manual for information on configuring and calibrating zero and full-scale values.
The load resistance vs. loop supply voltage graph below shows the minimum voltage required to power the instrument
for a given loop resistance. In addition, the mathematical relationship between loop voltage and load resistance is given.
For example, if a power supply voltage of 24 volts is available to power the current loop, the maximum load resistance
would be 800 ohms. Wire as shown in Figure 3.14 .
Figure 3.14 - Analog (4 to 20 mA) output wiring
1000
800
400
0
8 18 24 30
LOOP SUPPLY VOLTAGE (VDC)
L
O
A
D
R
ES
IS
T
A
N
C
E
(
O
H
M
S
)
OPERATING
REGION
Figure 3.15 - Analog (4 to 20 mA) output
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Section 3 Scanner 3300 EFM