AMETEK XG Family Programmable DC - Manual (Page 59)

Local Operation
M370430-01 Rev E 3-13
3
Automatic Mode Crossover
Mode crossover occurs when the unit makes the switch between
operating modes. Crossover can occur from CV to CC or vice versa,
depending on how the attached load resistance changes. Figure 3-3
shows the relationships between the variables.
For example, if the unit was initially operating in CV mode with the
output voltage at the voltage set point and the load current below the
I
SET
and the attached load resistance began to decrease, the current
would rise to meet this change in the load. The load current will increase
in proportion to the decrease in the load resistance until the load current
drawn reaches the current set point. At this point further decreases in
load resistance (increased load current requirements) will cause the unit
to cross over into CC mode where the output voltage will vary with
changing load resistance and the load current will remain at the I
SET
value.
The reverse operating mode change can also occur if the load resistance
is increased to the point that the required load current drops below the
I
SET
value. At that point the power supply would crossover to CV mode
and the load current would be free to vary as the load resistance
changed.
L
o
a
d
c
u
rr
e
n
t
(V
)
L
o
a
d
c
u
rr
e
n
t
(A
)
Iset
Figure 3-3 Operating Modes
CV mode
Crossover point
CV mode
Vset
Load current
Load voltage
Load resistance ( Ω