Balluf BIS M-41 Series, Technical Description Manual

Page: 23 / 44

BIS M-41_ USER'S GUIDE
16
2
2.4.3 Cable Voltage Drop
In addition, each RFID compact processor 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 Compact Processor Current x Number of Compact processors) 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-410-067-
001-04-S92 compact processors (87 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 RFID compact processor 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 compact processor and not the eighth to be the furthest
from the power supply.
Voltage Drop = [0.133 A GWY + (0.087 A x 8 compact processors)] x [(0.058 x 2) x 20
meters] = 1.92 Vdc total voltage drop for 8 compact processors
24 Vdc - 1.92 /2 = 23.04 Vdc at compact processor 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).