Innotech Genesis II Digital Controller (v5) - Manual (Page 121)

Page 121
Genesis II Installation Instructions
© Mass Electronics Pty Ltd 2010 Chapter 5 – Network Installation
5-4 Cable Connection Procedures
This paragraph contains general procedures for the connection of Comms cables and checks to
ensure there are no hazardous voltages present.
The ideal situation would be that the voltages measured between the data conductors, between the
data conductors and the screen and between the data conductors, the screen and the earthed parts
of a device were 0VAC and 0VDC. In practice this will not be the case. These measurements should
be made before connecting any Comms cables to ensure that these voltages are within the specified
ratings of the RS485 ICs.
It is important to test all data conductors and the screen because only one conductor may be faulty if
the cable was damaged during installation.
The measured AC voltage is the RMS (effective) value but the ICs are subjected to the peak value of
voltages. Therefore, the AC values in the tests must be less than the DC values.
The following procedures should be performed in the order shown before application of power to the
system:
1. Ensure there are no network cables connected to any device.
2. Connect the supply conductors to all devices, ensuring that, where it is specified, the electrical
earth is connected to the device.
3. Ensure that no conductors or screens of the network cables are in contact with any device or
any metal.
4. Select the network device that is to be the earthing point for the network cables.
5. Before connecting the network cable to the selected device, check if there is a voltage difference
between the test points on the cable and the device as shown in Figure 5-19 through to Figure
5-21 , as appropriate.
6. If the voltages are less than the values shown in Figure 5-19 through to Figure 5-21 , then
connect the network cable(s), including the screen to the device selected in Step 4, above.
7. For looping connections, test the two cables separately before connecting them.
8. Go to the device to be connected to the other end of the section of network cable.
9. Before connecting the network cable to this next device, check if there is a voltage difference
between the test points on the cable and the device as shown in Figure 5-19 through to Figure
5-21 , as appropriate.
10. If the voltages are less than the values shown in Figure 5-19 through to Figure 5-21 , then
connect this section to the device. If the cable is looping onto the next device, test the next
section of network cable before connecting the cables.
11. A resistance check between the screen and a point connected to the electrical earth can confirm
the integrity of the screen at each stage of the connection process.
12. Continue testing and connecting one section at a time, moving away from the earthing point.