User`s guide
2 Installation
34 Model N6705 User’s Guide
Wire Size and Length
WARNING
FIRE HAZARD Select a wire size large enough to carry short-circuit current
without overheating (refer to the table below). To satisfy safety require
ments,
load wires must be heavy enough not to overheat while carrying the short-
circuit output current of the unit. Agilent Model N678xA SMU wiring
requirements are described on the following page.
Along with conductor temperature, you must also consider voltage
drop when selecting wire sizes. The following table lists the
resistance for various wire sizes and the maximum lengths to limit
the voltage drop to 1.0 V per lead for various currents.
Note that the minimum wire size required to prevent overheating
may not be large enough to prevent over-voltage tripping or maintain
good regulation. Under most conditions, the load wires should also be
heavy enough to limit the voltage drop to no more than l.0 V per lead.
To help prevent nuisance tripping of the over-voltage circuit, select a
wire size sufficient to handle the FULL output current of the unit no
matter what the intended load current or current limit setting
Load lead resistance is also an important factor relating to the CV
stability of the instrument when remote sensing capacitive loads. If
high capacitance loads are expected, you should not use wire gauges
heavier than 12 to 14 AWG for long runs of load lead.
Wire size Current-carrying capacity in Amps
for stranded copper wire
Resistance Max. Length to Limit Voltage to 1 V/Lead
for 5 A for 10 A for 20A for 50 A
AWG 2 wires bundled 4 wires bundled
Ω
/foot Wire length in feet
20
7.8
6.9
0.0102
20
x
x
x
18
14.5
12.8
0.0064
30
15
x
x
16
18.2
16.1
0.0040
50
25
x
x
14
29.3
25.9
0.0025
80
40
20
x
12
37.6
33.2
0.0016
125
63
30
x
10
51.7
45.7
0.0010
200
100
50
20
8
70.5
62.3
0.0006
320
160
80
32
6
94
83
0.0004
504
252
126
50
Area in mm
2
2 wires bundled 4 wires bundled
Ω
/meter Wire length in meters
0.5
7.8
6.9
0.0401
5
x
x
x
0.75
9.4
8.3
0.0267
7.4
x
x
x
1
12.7
11.2
0.0200
10
5
x
x
1.5
15.0
13.3
0.0137
14.6
7.2
x
x
2.5
23.5
20.8
0.0082
24.4
12.2
6.1
x
4
30.1
26.6
0.0051
39.2
19.6
9.8
3.9
6
37.6
33.2
0.0034
58
29
14.7
5.9
10
59.2
52.3
0.0020
102
51
25
10.3
Notes: 1. Capacity for AWG wires derived from MIL-W-5088B. Max. ambient temp: 55°C. Max. wire temp: 105°C.
2. Capacity for metric wires are derived from IE Publication 335-1.
3. Capacity of aluminum wire is approximately 84% of that listed for copper wire.
4. “x” indicates wire is not rated for the maximum output current of the power module.
5. Because of wire inductance considerations, it is also recommended that you keep your load leads twisted, tie wrapped,
or bundled together and less than 50 feet (14.7 meters) in length per lead.