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Introduction
11
Power and Status
The Power and Status section encompass the power switch and displays the status of the
timebase and remote interface(s):
Status Indicators
REF / SYNTH
On the far right portion of the front panel are two groups of LED
indicators. The upper group is labeled REF / SYNTH and indicates the
status of the internal timebase. The EXT LED indicates that the
instrument has detected an external 10 MHz reference at the timebase
input BNC on the rear panel. If detected, the instrument will attempt to
lock its internal clock to the external reference.
The LOCK LED indicates that unit has locked its internal frequency
synthesizer at the requested frequency. Normally this LED will only
extinguish momentarily when the frequency changes or an external
timebase is first applied to the rear input. If the LED stays off, it indicates
that the signal generator may be unable to lock to the external timebase.
This is most commonly caused by the external frequency being offset by more than
2 ppm from 10 MHz.
INTERFACE
The lower group of LED indicators is labeled INTERFACE. These LEDs indicate the
current status of any active remote programming interface (Ethernet, RS-232, or GPIB).
The REM (remote) LED turns on when the unit is placed in remote mode by one of the
remote interfaces. In this mode, all the front panel keys are disabled and the instrument
can only be controlled via the remote interface. The user can return to normal, local
mode by pressing the [3] key (also labeled [LOCAL]). The ACT (activity) LED flashes
when a character is received or sent over one of the interfaces. This is helpful when
troubleshooting communication problems. If a command received over the remote
interface fails to execute due to either a parsing error or an execution error, the ERR
(error) LED will turn on. Information about the error is available in the STATUS
secondary display. See page 24 for more detailed information on how to access this
display.
POWER
The power switch has two positions: STANDBY (button out) and ON (button in).
In STANDBY mode, power is only supplied to the internal timebase and the power
consumption will not exceed 25 watts. In ON mode, power is supplied to all circuitry
and the instrument is on.
Stanford Research Systems
SG390 Series RF Signal Generators