Agilent Technologies 66001A Output Connections, Selecting the Proper Wire Size, Resistance Ω/ft

Output Connections

Before making the actual connections, you must decide on the system configuration. The following factors are described in the rest of this chapter:

■using the correct wire size

■maintaining isolation guidelines

■selecting local or remote voltage sensing

■connecting modules in series or in parallel

■using output relays

■connecting to capacitive or inductive loads

Selecting the Proper Wire Size

Fire Hazard. To satisfy safety requirements, load wires must be large enough not to overheat when carrying the short-circuit output current of the device connected to the power module. See Table 2-2 for the characteristics of AWG (American Wire Gage) copper wire.

Table 2-2. Current Capacity and Resistance of Stranded Copper Conductors

AWG No.

20

18

16

14

*Ampacity

8.33

15.4

19.4

31.2

**Resistance

(Ω/m Ω/ft)

0.0345 0.01054

0.0217 0.00663

0.0137 0.00417

0.0086 0.00262

AWG No. *Ampacity

1240

*In free air

**Resistance

(Ω/m Ω/ft)

0.0054	0.00165
**At 20 °C

Output Isolation

The output connector ground terminal is a low-noise ground provided for convenience, such as for grounding wire shields. This terminal is not designed to function as an equipment safety ground.

The power module output terminals are isolated from earth ground. If required, either output terminal may be grounded.

The potential between either output terminal and ground must not exceed ±240 Vdc. Failure to observe this restriction may damage the power module.

Local Voltage Sensing

Figure 2-4A shows the load connection for local sensing. There is a switch on the output connector that selects either local or remote sensing of the output voltage. The connector is shipped with the switch in the LOCAL position. In order to configure the output for local sensing, make certain this switch is set to LOCAL.

Note The position of the Local/Remote switch also can be determined by software (see

VOLT:SENS:SOUR? in "Chapter 3 - Language Dictionary" of the Programming Guide).

With local sensing, the power module voltage readback circuit senses the voltage at the output terminals. Since this does not compensate for voltage drops in the terminal screw connections and output leads, use Local sensing only in applications requiring low output currents or where the load regulation is not critical.

Installation 21