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50 ST 3000 Release 300 and SFC Model STS103 User’s Manual 6/08
5.2 Establishing Communications
SFC connection rules
• Always plug the SFC leads into the jack on the SFC before you
connect them to the transmitter.
• Use this formula to find the maximum filter capacitance allowed
across the sense resistor (250 ohm minimum) for SFC
communications to work.
C (µF) = 1000 / R
sense
Connecting SFC
Using either leads with alligator clips or easy-hooks supplied with the
SFC, you connect the SFC directly to signal terminals on the
transmitter’s terminal block or at any convenient location in the 4 to 20
milliampere line. Observing polarity, connect the red lead to positive (+)
and the black lead to negative (–).
WARNING
When the transmitter’s end-cap is removed, the housing is not
explosionproof.
Figure 19 shows typical SFC connections across loop wiring to the
ST 3000 transmitter. (Non-lightning protection terminal connections
shown.)
Figure 19 Typical SFC Connections.
+ Red
- Black
+
-
Field
Terminals
-
S
I
G
N
A
L
+
+
-
T
E
S
T
STR3012
Power
Supply
+
-
Receiver
SFC
ST 3000
250
Ω
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