R&S NGU, User Manual

Page: 42 / 214

Operating basics
R&S
®
NGU
42 User Manual 1179.2531.02 ─ 03
V
out
V
set
Voltage regulation
I
out
I
max
Cu
rr
en
t c
on
tr
ol
Figure 5-11: Current limit
CC mode
The current I
max
corresponds to the current setting adjustable in the instrument.
If I
out
reaches I
max
, the instrument switches to CC mode, i.e. the output current remains
constant and limited to I
max
even if the load increases. Instead, the output voltage V
out
decreases below V
set
. In a short circuit, the output voltage drops towards zero. In CC
mode, the font text in the channel display area changes to red.
See Figure 5-3 and Chapter 6.8.1, "Overcurrent protection (OCP)" , on page 65.
CR mode
To go into CR mode, the R&S NGU must operate in sink mode where current flows into
the instrument and "Constant Resistance" are enabled.
With "Constant Resistance" enabled and configured, the R&S NGU can set the resist-
ance in sink mode, this allows the R&S NGU to behave like an electronic load which is
useful in battery test application.
In CR mode, the font text in the channel display area changes to cyan.
See Figure 5-3 .
5.5.1 Voltage and current priority modes
By default, the R&S NGU uses voltage priority mode, VPM to regulate output. In this
mode, the output is controlled by a bipolar voltage control loop. In VPM, the output cur-
rent can be set to the required positive and negative limits.
Operation modes