Sensaphone SCADA 3000 Users manual - Manual (Page 271)

26-3
Chapter 26: Analog Output Module
The two LED lights in the center of the module, marked Power and Pulse, indicate that the
module is receiving power and operating properly. The Pulse LED will blink at a regular rate,
like a heartbeat, once it establishes communication with the main unit.
Communications Wiring
The Analog Output Module communicates with the SCADA 3000 using a high-speed serial
communications bus. This 4-wire bus is used to connect up to 15 modules to the main unit
to provide additional inputs and/or outputs. The communications cable must be 4-Conductor
Twisted Pair. You may use unshielded cable in electrically quiet environments, but be sure to
use shielded cable if your cabling must navigate around electrical machinery or equipment.
Modules may be located a maximum of 2000' away from the main unit and should be con-
nected in a daisy-chain fashion from one module to the next. Each module connects to the next
via a 4-wire communications cable connected to the terminals labeled A,B, Y & Z. The cable
must be 4-Conductor Twisted Pair (shielded or unshielded) with a nominal impedance of
120W (for example, Belden #8132 or 9842 cable). Use one pair for A & B and the other pair
for Y & Z. Note how the wiring is reversed between the first module and the main unit but
between modules the wiring is straight-thru. Correct wiring is shown in Figure 3, and incorrect
in Figure 4.
Figure 3: Correct daisy chain setup: Main unit on the end.
Figure 4: Incorrect daisy chain setup: Main unit in the middle of the chain.
The Main Unit should always be on one end of the chain, never in the middle.
Cabling Notes
Follow these guidelines to protect the communications cable from electrical interference.
• Keep the communications cable at least five feet from any electric motors, trans-
formers, rectifiers, generators, arc welders, induction furnaces, or sources of
microwave radiation.
• If you must run the cable across power lines, run them at right angles to the lines.
• Keep the communications cable at least 6 inches from AC power lines carrying
less than 20A, at least 1 foot from lines greater than 20A, and 2 feet from lines
greater than 100KVA.