Agilent Technologies 6811B, 6813B Remote Sense Connections, Wire Considerations, Voltage Drops

Installation - 2

Wire Considerations

NOTE: To minimize the possibility of instability on the output, keep load leads as short as possible bundle or twist the leads tightly together to minimize inductance

Current Ratings

Fire Hazard To satisfy safety requirements, load wires must be large enough not to overheat when carrying the maximum short-circuit current of the ac source. If there is more than one load, then any pair of load wires must be capable of safely carrying the full-rated current of the ac source.

Table 2-1 lists the characteristics of AWG (American Wire Gage) copper wire.

Table 2-1. Ampacity and Resistance of Stranded Copper Conductors

AWG No.

14

12

10

8

Ampacity1

25

30

40

60

Resistance2

(Ω/m)

0.0103

0.0065

0.0041

0.0025

AWG No.

6

4

2

1/0

Ampacity1

80

105

140

195

Resistance2

(Ω/m)

0.0016

0.0010

0.00064

0.00040

NOTES:

1.Ampacity is based on 30°C ambient temperature with conductor rated at 60°C. For ambient temperature other than 30°C, multiply the above ampacities by the following constants:

Temp. (°C)	Constant	Temp. (°C)	Temp. (°C)
21-25	1.08	41-45	0.71
26-30	1.00	46-50	0.58
31-35	0.91	51-55	0.41
36-40	0.82

2. Resistance is nominal at 75 °C wire temperature.

Voltage Drops

The load wires must also be large enough to avoid excessive voltage drops due to the impedance of the wires. In general, if the wires are heavy enough to carry the maximum short circuit current without overheating, excessive voltage drops will not be a problem. Refer to Table 2-1 to calculate the voltage drop for some commonly used AWG copper wire. If load regulation becomes a problem refer to the section "Remote Sense Connections".

Remote Sense Connections

Under normal operation, the ac source senses the output voltage at the output terminals on the back of the unit. External sense terminals are available on the back of the unit that allow the output voltages to be sensed at the load, compensating for impedance losses in the load wiring. As shown in the following figure:

25