Rice Lake 420 Plus HMI Digital Weight Indicator Installation Manual - Manual (Page 13)

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420 Plus Installation Manual - Installation 9
Figure 2-5. 420 Plus DC Power Supply
2.3.3 DC Power Wiring Guidelines
Based on:
• 8 x 350 
• Analog output installed
• Digital outputs sourcing 20mA each
• Drawing maximum current at 7.5 VDC from
the DC/DC power supply
Note
DC power wiring to the indicator should be 18
AWG to 14 AWG for DC+, DC-, and earth
ground conductors.
In a mobile application, earth ground (chassis) should
be terminated to the vehicle chassis.
In longer power cable runs, voltage drop over the
power conductor needs to be considered. See table and
formula below to compute voltage drop.
V
DROP
= (2.85A)(x  / 1000ft)(length of run in ft.)
2.85A = maximum current draw from DC/DC power
supply
x
 = Ohms from Table 2-1
Table 2-1. Cable Impedance
Wire Gauge
(AWG)
Cable
Impedance
(OHMS/1000ft)
14 2.252

15 3.184

16 4.016

17 5.064

18 6.385

Note
DC voltage supplied to DC/DC power supply
should not be less than 9VDC. Using larger
gauge wire will result in less voltage drop.
Example:
100ft run with 18 AWG wire
V
DROP
= (2.85A)(6.385  / 1000ft)(100 ft)
V
DROP
= 1.82V
12VDC will drop to 10.18V after 100ft run.