Balluff BIS M-370-000-A02, Manual, Page: 47 / 198

BIS M-62_ MANUAL
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2.4.3 Cable Voltage Drop
In addition, each RFID Processor unit on the Subnet will experience a certain amount of
voltage drop depending on the length of the cable.
Cable Resistance per Meter

ThinNet = 0.058 ohms per meter per wire

ThickNet = 0.0105 ohms per meter per wire
Calculating Voltage Drop
Voltage Drop = (Max Processor unit Current x Number of Processor units) x (Cable
Resistance per Meter per Wire
1
x Cable length in Meters)
Example
A Subnet16
™ network is composed of a BIS Z-GW-001- connecting eight BIS M-620-067-
A01-04-_ Processor units (366 mA each @ 24 Vdc). A total of 20 meters of ThinNet cables
are used to connect the devices, which have Cable Resistance = 0.058 Ohms per meter per
wire. The network power is 24 Vdc.
The voltage drop calculation must be conducted on the processor unit that is farthest from
the Power Supply, as it will experience the greatest voltage drop.
NOTE
It is always recommended to power the network from the middle (T-
configuration), to reduce total voltage drop at the ends. In the example below
this allows the fourth processor unit and not the eighth to be the furthest
from the power supply.
Voltage Drop = [0.133 A GWY + (0.366 A x 8 Processor units)] x [(0.058 x 2) x 20
meters] = 7.10 Vdc total voltage drop for 8 Processor units
24 Vdc - 7.10 /2 = 20.45 Vdc at processor unit number 4 of each branch
2.4.4 Current Rating for Cables
The maximum current rating for the Subnet16™ network using Balluff cables and
accessories (BCCxxxx), is
4.0 A .
1
The resistance calculation must include both wires (Vdc and GND).