Kentec Electronics Sigma A-CP - Page 102

3 Identify the maximum resistance of the wire gage used in the circuit (R
wiremax
) when using 18 AWG copper.
An 18 AWG solid copper wire is 6.385 Ohms at 1000 FT using the Resistance Table below:
Gage Resistance / 1000 FT @ 68
o
F R
wire
18 AWG
6.385 Ω (Ohms) 0.006385 Ω / FT
16 AWG
4.016 Ω 0.004016 Ω / FT
14 AWG
2.525 Ω 0.002525 Ω / FT
4 The minimum NAC output voltage:
5
Identify the voltage-drop (V
drop
) across the length of the wire:
V
drop
= V
outmin
- V
opmin
= 18 VDC - 16 VDC
6 Identify the maximum wire length (L
max
) of this circuit:
L
max
= 1/2 ( V
drop
/ I
max
) / R
wire
where,
= 1/2 [ ( 2 / 0.6286 ) / ( 0.006385 Ohms / FT ) ]
V
NAC
-
min
= 20.4 VDC
V
drop
= 2 VDC
L
max
= 249 FT
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