Programming Output Protection
Set the Over-Voltage Protection
Set the Over-Current Protection
Output Watchdog Timer
User-Defined Protection
Clear Output Protection Functions
Protection Shutdown Behavior
Introduction
The APS models have many protection functions. These functions disable the output to protect the
device under test as well as the power supply. A front panel status indicator will turn on when a
protection function has been set. Most protection functions are latching, which means that they must
be cleared once they have been set. Of the following protection functions, the OV, OC, PROT, INH, and
UProt are user-programmable.
OV Over-voltage protection is a hardware OVP whose trip level is a user-programmable value. Over-voltage protection also occurs
automatically if the remote sense leads are shorted. OV protection is always enabled.
OV- Negative over-voltage protection detects if the remotesense leads are reversed. Atinstrument turn-on, italso detects if voltages
more negative than -2V are present at the output terminals. OV- protection is not programmable and is always enabled.
OC Over-current protection is a user-programmable function that can be enabled or disabled. When enabled, the output will be dis-
abled when the output reaches the current limitsetting.
CP+ Positive over-power compares the output power against a built-in threshold. A CP+ protection occurs when the threshold is
exceeded. CP+ protection is always enabled.
CP- Negative over-power compares the internally dissipated power against a built-in threshold. A CP- protection occurs when the
threshold is exceeded. CP- protection is always enabled.
OT Over-temperature protection monitors the internal temperature of the power supply and disables the output if the temperature
exceeds the pre-defined limit(seeOUTPut:PROTection:TEMPerature:MARGin?). Note that sensor information from any
connected power dissipator is combined with the information from the power supply into a single indicator. OT protection is
always enabled.
PF Power-fail indicates that a power fail condition on the AC mains has occurred and has disabled the output. PF protection is
always enabled.
EDP Excessive dynamic protection disables the output in the event of excessive large repetitive voltage swings caused by pro-
grammed voltage changes, lists, Arbs, or load-induced voltage swings (see Output Dynamic Response). If unchecked,
these voltage swings could result in premature failure of components in the instrument. EDP protection is always enabled.
Prot Prot indicates the output is disabled because the programmed output watchdog timer expired.
INH The Inhibitinput (pin 3) on the rear panel digital connector can be programmed to act as an external shutdown signal. Refer to
Inhibit Input for further information.
UProt A User-defined protection condition has disabled the output.
4 Using the Advanced Power System
112 Keysight N6900/N7900 Series Operating and Service Guide
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