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46 Front Panel Operation
Clearing The OVP Condition
With the OVP tripped, return to the meter mode and try to clear the condition by pressing
. Nothing will appear
to happen because the OV trip voltage is still below the programmed output voltage. Thus, as soon as the circuit is cleared,
it trips again. You can clear the OV condition by:
■ Lowering the output voltage below 48 (the OV setting), or
■ By raising the OV trip voltage above the output voltage setting.
Try either of these methods. Now when you press
, the Prot annunciator will turn off and the output voltage will
return to normal.
Programming Overcurrent Protection
When enabled, overcurrent protection removes the Agilent SAS output whenever it goes into CC operation. This prevents
the unit from indefinitely supplying the full programmed current to the load.
Note This constant-current OCP feature is only available in Fixed mode. In Simulator and Tables modes, a
hardware current limit protection circuit turns the unit off when a programmable current limit is reached.
This current limit is only programmable over the GPIB using SOUR:CURR:PROT.
Setting The OCP Protection
To activate overcurrent protection, press
. The OCP annunciator will light and Agilent SAS will continue to operate
normally until it is forced into CC operation. If that occurs, the OCP circuit trips and the Agilent SAS output drops to zero.
Checking OCP Operation
The easiest way to check this operation at any specified current is to increase the load current beyond the programmed
current value. This will force the Agilent SAS into the CC mode. When OCP trips, the Prot annunciator will light and the
Agilent SAS output will drop to zero.
There is now no Ahilent SAS output due to an overcurrent condition. To verify this, press
and observe that the
display indicates OC.
Clearing The OCP Condition
With the OCP tripped, return to the meter mode and try to clear the condition by pressing
. Nothing will appear to
happen because the reason for the condition has not been removed. Thus, as soon as the circuit is cleared, it trips again. You
can clear the OC condition by:
■ Increasing the load resistance to lower the output current below the programmed current value, or
■ By raising the programmed current to a value above that required by the load.
Clear the fault by either of the above methods. Then clear the OCP circuit by pressing
. The Prot annunciator will
go off and the Agilent SAS output will be restored to normal. If desired, you can also restore the output by disabling the
OCP function (press
to turn off the OCP annunciator). This restores the output but does not clear any condition that
may have caused OCP to trip.
Note Under certain conditions, the OCP circuit may fail to clear because load demand occurs before the Agilent
SAS has time to build up the required output current capacity. In such cases, disable the output (press
before clearing the OCP circuit). After OCP is cleared, then enable the Agilent SAS output.