Agilent Technologies N8900 series Operating Manual page 56

You can also specify an OCP delay to prevent momentary output settings, load, and status changes from tripping the
over-current protection. In most cases these momentary conditions would not be considered an over-current pro-
tection fault, and having an OCP condition disable the output when they occur would be a nuisance. Specifying an OCP
delay lets the OCP circuit ignore these momentary changes during the specified delay period. Once the OCP delay time
has expired and the over-current condition persists, the output will shut down.
Front Panel Menu
Select Protect\OCP
Enter a delay value. Then press Select.
Factors that influence how long the settings change or output load change may last include: difference between old out-
put value and new output value, the current limit setting, and the load capacitance in CV mode or load inductance in CC
mode. The delay required must be determined empirically; the output programming-response time characteristics may
be used as guidelines.
Note that the time it takes the output to go into CC mode varies - depending on the magnitude of the over-current con-
dition compared to the current limit setting. For example, if the over-current is only slightly greater than the current
limit setting, it may take several tens of milliseconds for the output to set the CC status bit. If the over-current is sig-
nificantly greater than the current limit setting, it may only take a few hundred microseconds or less for the output to
set the CC status bit. To determine when the output will shut down, you must add the time it takes for the CC status
bit to the over-current protection delay time. If the over-current persists beyond the sum of these two time intervals,
the output will shut down.
Clear Output Protection
If an over-voltage, over-current, over-temperature, power-fail condition, or master/slave protection occurs, the output
is disabled. The appropriate operating status indicator on the front panel will be on. To clear the protection function and
restore normal operation, first remove that condition that caused the protection fault. Then, clear the protection func-
tion as follows:
Front Panel Menu
Select Protect\Clear
Select Clear.
MSP protection cannot be cleared using Protect\Clear. It can only be cleared by cycling power or re-
discovering the slave units (see
Agilent N8900 Series Operating and Service Guide
SCPI Command
To specify a 10 millisecond delay:
CURR:PROT:DEL 0.01
SCPI Command
To clear a protection fault:
OUTP:PROT:CLE
Group Configuration).
Programming Output Protection
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