N7976A, N7977A models and
N6976A, N6977 models with relay
options
Due to the higher voltage capability of these models, they are equipped with
a fast solid-state disconnect switch (< 5 µs turn-off time) in series with the
galvanic relays. When a protection event occurs, the solid-state switch opens
after the 2 ms down-programming period. Following this, the galvanic relays
will open after their 20 ms delay has elapsed.
Customizing the Shutdown Behavior
This feature is available on firmware revision A.01.13 and up.
If your device under test has energy sourcing capability as is the case for batteries, power supplies, or
large capacitors, the down-programming capability of the protection function could cause undesirable
effects on the device under test.
Therefore, you can customize the protection shutdown behavior according to the following selections:
Low Impedance - the output voltage is programmed to zero, then disconnected. Maximum negative
current sinking occurs for 2 ms during the turn-off transition. This is the default protection behavior as
described in the previous table.
High Impedance - the output is disconnected without actively sinking current. Without active current
sinking, output energy will take longer to dissipate - as downprogramming is solely determined by the
unit's passive internal network.
The following command lets you configure the turn-off behavior for all protection conditions:
Front Panel Menu Reference SCPI Command
Select Protect\Mode
Check either High Impedance or Low Impedance. Then
press Select.
To selectHigh impedance mode:
OUTP:PROT:MODE HIGHZ
To selectLow impedance mode:
OUTP:PROT:MODE LOWZ
When switching modes from Voltage Priority to Current Priority and vice-versa, the
mode setting reverts to Low Impedance mode for safety reasons.
If a power-fail shutdown fault occurs on models with output voltages greater than
60 V, the down-programmer circuit remains enabled for this fault condition for
safety reasons.
4 Using the Advanced Power System
116 Keysight N6900/N7900 Series Operating and Service Guide
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