Bray 70 Series SERVO PRO DeviceNET - Manual (Page 11)

S70 DeviceNet Servo Installation & Maintenance Manual
2000 BRAY CONTROLS Page 10 of 24
Figure 5: Example of Network connection with tap, Trunk line, and Drop line.
Specifications 125 Kbps Data Rate 250 Kbps Data Rate 500 Kbps Data Rate
Thick trunk length 500 m (1640 ft) 250 m (820 ft) 100 m (238 ft)
Thin truck length 100 m (328 ft) 100 m (328 ft) 100 m (328 ft)
Max drop length 6 m (20 ft) 6 m (20 ft) 6 m (20 ft)
Cummulative drop length 156 m (512 ft) 78 m (256 ft) 39 m (128 ft)
Table 3: DeviceNet Cable Lengths
3.1.2 Network Grounding and Isolation
To prevent ground loops, the DeviceNet network should be earth grounded in only one location.
The physical layer circuitry in all devices is referenced to the V- bus signal. Connection to earth
ground is provided at the bus power supply and is discussed in Section 3.1.3. No current flow
between V- and earth ground may occur via any device other than a power supply. A ground
isolation barrier must exist for every device. The S70 Servo V- bus signal is entirely isolated
from ground and is not affected by the grounding of the S70 Actuator. Since the S70 Actuator is
powered from the line voltage, the body of the S70 Actuator is connected to earth. A safety
hazard may exist if the earth ground connection to the S70 Actuator body is removed.