User`s guide

5 Operation and Connections Tutorial
102 Model N6705A User’s Guide
The sense leads carry only a few milliamperes of current and can be
a 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).
1. Twist leads
2. 4-wire
enabled
(indicator
is on)
Open Sense Leads
The sense leads are part of the output's feedback path. Connect them
in such a way so that they do not inadvertently open. The DC Power
Analyzer includes protection resistors that reduce the effect of open
sense leads during 4-wire sensing. If the sense leads open during 4-
wire sensing, the DC Power Analyzer returns to local sensing mode,
with the voltage at the output terminals approximately 1% higher
than the programmed value.
Over-voltage Protection Considerations
You must take into account any voltage drop in the load leads when
setting the over-voltage trip point. This is because the OVP circuit
senses at the output terminals and not at the sense terminals. Due to
the voltage drop in the load leads, the voltage sensed by the OVP
circuit could be higher than the voltage being regulated at the load.
Output Noise Considerations
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 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 DC Power Analyzer 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 tantalum capacitor, with an approximate value of 10 μF
per foot (30.5 cm) of load lead, right across the load.
1
+
2