Electro-Voice 250, 1252 operation manual 11 RS-485 Connection-Nexus Meter to Nexus I/O Modules

5.11: RS-485 Connection—Nexus Meter to Nexus I/O Modules

Six feet of RS-485 cable harness is supplied. Insert one end of the cable into Port 4 of the Nexus 1250/1252 Meter.

Insert the other end of the cable into the I/O module’s female RS-485 side port (see Figure 5.9). The connectors fit only one way into the ports.

Use the male RS-485 side port to attach another I/O module. The Nexus 1250/1252 will power up to four connected I/O modules using 15–20V DC at 50–200mA, represented by dashed lines in the figure below. Use the steps below (section 5.12) to determine if you must use a separate power source (for example, EIG PSIO) to supply added power to the group. RS-485 communication is viable for up to 4000 feet (1219 meters). However, if your cable length exceeds 200 feet, use the remote power supply and:

•Connect the A(+) and B(-) terminals on the Nexus to the A(+) and B(-) terminals of the female RS-485 port. Connect the shield to the shield (S) terminal. The (S) terminal on the Nexus 1250/ 1252 is used to reference the Nexus port to the same potential as the source. It is not an earth ground connection. You must also connect the shield to earth-ground at one point.

•Provide termination resistors at each end, connected to the A(+) and B(-) lines. RT is approximately 120 Ohms. NOTE: Refer to section 5.3 for RT Explanation.

A(+) B(-) S - V +

Male Side Port on Nexus I/O Module

RT

RT

Nexus Meter Port 4

+ V - S B(-) A(+)

Figure 5.13: Nexus Meter Connected to Nexus I/O Module

Electro Industries/GaugeTech Doc # E107706 V1.25 5-14