Front Panel Operation
58
n Press . If you discover a mistake before pressing , erase the incorrect value with the backspace
key .
n The display will return to the meter mode and indicate up to 1.3000 amperes, depending upon the load.
Now raise the current by pressing (or rotating the Current control clockwise). Note that the current increases by
a specific increment (depending on the current resolution) each time you press the key and increases rapidly as you hold
down the key. To lower the current, press rotate the Current control counterclockwise.
Try to program a current greater than the IMAX for your supply. Note that the display shows OUT OF RANGE.
CV Mode vs. CC Mode
Once you program a voltage (V
s
) and a current (I
s
), the power supply will try to maintain itself in either CV or CC mode,
depending on the resistance of the load (R
L
). If the load demands less current than I
s
, operation will be in CV mode with the
voltage maintained at V
s
. The output current will be at some value below Is as determined by V
s
÷ R
L.
For an Agilent 6552A supply, I
MAX
= 25.594 amperes and V
MAX
= 20.475 volts. If you program the output for <≤25
amperes at 20 volts, the supply will operate in the CV mode for all resistances >0.8 ohms. This represents the operating
resistance shown as R
L
= C in Figure 5-2. The supply will vary the output current to maintain a constant voltage of 25 volts.
If the load resistance is <0.8 ohms, the supply will vary its output voltage to maintain a constant current output of 25
amperes. However, if you reprogram the output voltage to a lower value Vs (see Figure 5-2), then the supply will again be
able to maintain CV operation with the lesser load resistance, such as R
L
=B in Figure 5-2.
Programming Overvoltage Protection
Overvoltage protection guards the load against voltages that reach a specified value above the programmed output voltage.
Setting the OVP Level
Assuming that a power supply is programmed for 10 volts, you can set the OVP level to 11.5 volts as follows:
n Press . The display will change from meter mode to indicate 0V, followed by the present OVP value.
n Press .
n The display will return to the meter mode and indicate the output (10.000 volts).
n Press again. The display will now indicate 0V 11. 500.
n Press to return to the meter mode.
Checking OVP Operation
Assuming the above operating conditions, trip the OVP circuit as follows:
• Raise the output voltage close to the trip point, such as 11.0.
• Gradually increase the output voltage by pressing until the OVP circuit trips. This will cause the output
voltage to drop to zero and the Prot annunciator to go on.
• There now is no power supply output due to an overvoltage condition.
• To verify this, press and observe that the display indicates 0V.
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