Sensaphone SCADA 3000 Users manual - Manual (Page 257)

24-3
Chapter 24: Pulse Count Module
It is extremely important that the EG pin be connected to a good earth ground. This will pre-
vent communication errors due to differences in ground potential between modules in addition
to possible damage due to voltage transients and surges.
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, to indicate that the unit is functioning.
COmmUNICATIONS WIRING
The Pulse Count Module communicates with the SCADA 3000 using a high-speed serial com-
munications bus. This 4-wire bus is used to connect up to 15 modules to the main unit to pro-
vide additional inputs and/or outputs.
Modules may be located a maximum of 2000' away from the main unit and should be connect-
ed 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). 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. Power for the expansion modules is provided
at the terminals labeled Aux Power on the main unit (see POWER section above). The proper
wiring from the main unit to the modules, and from module to module, is shown in Figure 3:
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.
Each module must be configured with its own unique address using the BUS ADDRESS
jumpers. You may mix & match up to 15 modules to suit your application’s requirements. The
following example shows a Bus Address setting of 9.