Remote Sense Connections - Agilent Technologies N6751A User Manual

2 Installation

Remote Sense Connections

Open Sense Leads
Output Noise Considerations
24
Remember to turn off the power system before making or changing
any connections on the rear panel terminal blocks. Connect the unit
for remote sensing by first disconnecting the straps between sense
and load terminals. Make your connections as shown in the previous
figure. Connect the sense leads as close to the load as possible. Refer
to the "Wire Size" section for information about selecting the proper
wire size. Best results are obtained by using the shortest load leads
practical. It is recommended that you keep your load leads under
14.7 meters (50 feet) per lead because of inductance effects.
The sense leads carry only a few milliamperes of current and
therefore, can be lighter gauge than the load leads. However, note
that any voltage drop in the sense leads can degrade the voltage
regulation of the instrument. Try to keep the sense lead resistance
less than about 0.5Ω per lead (this requires 20 AWG or heavier for a
50 foot length).
The sense leads are part of the output's feedback path. Connect them
in such a way so that they do not inadvertently become open
circuited. The power system includes protection resistors that reduce
the effect of open sense leads during remote-sensing operation. If the
sense leads open during operation, the power system returns to the
local sensing mode, with the voltage at the output terminals
approximately 1% higher than the programmed value.
Any noise picked up on the sense leads will appear at the output
terminals and may adversely affect CV load regulation. Twist the
sense leads or use a ribbon cable to minimize the pickup of external
noise. In extremely noisy environments it may be necessary to shield
the sense leads. Ground the shield at the power system end only; do
not use the shield as one of the sensing conductors.
The noise specifications in Appendix A apply at the output terminals
when using local sensing. However, voltage transients may be
produced at the load by noise induced in the leads or by load current
transients acting on the inductance and resistance of the load lead. If
it is desirable to keep voltage transient levels to a minimum, place an
aluminum or a tantalum capacitor, with an approximate value of 10
µF per foot (30.5cm) of load lead, right across the load.
Series N6700 User's Guide