3.2 OPERATING MODES
The voltage and current controls set the boundary limits for the load voltage and current
respectively. The relationship between the control settings and the load resistance determines
whether the power supply operates in
constant voltage
or
constant current
mode. Automatic
crossover between modes depends on the followings:
Ÿ
The load connected to the output terminals of the power supply R
L
.
Ÿ
The front panel voltage control setting V
set
.
Ÿ
The front panel current control setting I
set
.
Vset.
Iset
Short Circuit Load Pt.
Open Circuit Load Pt.
Voltage Mode Line
Crossover Point
Imax.
Vmax.
Current Mode Line
Rcrossover = Rcrs = Vset/Iset
R =R
L crs
R >R
L crs
R =R
L crs
Figure 3.2: Operating Modes
3.2.1 CONSTANT VOLTAGE MODE
The power supply will operate in this mode (Voltage Channel active) whenever the current
through the load is lower than that defined by front panel current control. In this mode, the
output voltage of the power supply is set by the front panel voltage control. The output
current is determined by the load and the V
set
.
3.2.2 CONSTANT CURRENT MODE
The power supply will operate in this mode (Current Channel active) whenever the voltage of
the load is less than that defined by front panel voltage control. In this mode, the output
current of the power supply is set by the front panel current control. The output voltage is
determined by the load and I
set
.
3.2.3 OUTPUT NULLING
See figure 3.2 operating modes diagram. When controlling the supply from the front panel
pots in constant voltage or constant current mode, the operation is as follows:
1. The voltage potentiometer may not drive the current in the output to zero when a short is
applied across output.
2. The current potentiometer may not drive the voltage in the output to zero when the output
is an open circuit.
83-473-000 Revision J
3 - 2
Operating Instructions
