Keysight Technologies RP7900 Series, Operating And Service Manual

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An SDP protection can only be cleared by turning off the RP7900 unit, correcting the problem, and
rebooting the RP7900 unit.
The SDS has a watchdog timer that will also put it into a safe state if communication
with the RP7900 unit is lost.
Controlling the SDS Using Externally Wired Controls
The SDS must still be connected to the RP7900 when being controlled externally.
The external control lines described in this section must be wired to the appropriate connectors on the
back of the SDS unit (see installation section). These external control lines provide an extra layer of
operator safety, as they allow the SDS to be programmed externally of the RP7900 power supply.
Customer-supplied Emergency Stop (ESTOP) Switch
If an Emergency Stop safety switch is not being used, you must short Remote
Interface pin 1 to pin 2 and pin 3 to pin 4. If the pins are not shorted, there will be a
SDP protection event - requiring power cycling.
The ESTOP safety switch must be a dual-channel normally-closed switch that when pressed, puts the
SDS in a latched, safe state that includes opening the main and sense relays and discharging the unit
under test. Pressing ESTOP is a latched safety state requiring the operator to reset the SDS to exit the
safe state. The ESTOP signals are located on the Remote Interface connector on the SDS rear panel.
The opening sequence in response to an ESTOP event is as follows:
1. Open the power relays
2. Open the sense relays
3. Disable the power supply output
4. Discharge the UUT
5. Remain in this latched safety state until the ESTOP event is removed and the RESET switch is
pressed
When the SDS is in ESTOP mode, the power supply indicates a status of Inhibit (INH). A SCPI query
can be used to determine the cause of the power supply inhibit.
It is recommended to provide a reset switch for the operator to clear the SDS condition and turn the
output back on (see Reset Switch).
Customer-supplied Reset Switch
RESET is a momentary-contact, operator input switch used to manually reset the SDS and exit the
latched safety state. Once the ESTOP switches are closed or any other error condition is rectified, the
operator must press the RESET switch to use the system again. The RESET switch must be an
Keysight RP7900 Series Operating and Service Guide 311
Appendix A Keysight SD1000A Safety Disconnect System