Stanford Research Systems DS345, Manual

Page: 43 / 139

DS345 Setup
2-27
AUTO-TEST AND CALIBRATION
Introduction
The DS345 has built-in test and calibration routines that allow the user to
quickly and easily test and calibrate virtually the entire instrument. [SHIFT]
[CALIBRATE] cycles the DS345 through the calibration menu. Self-test and
autocal are started by pressing any UNITS keys while the menu line is dis-
played.
SELF-TEST
The DS345's always executes a self-test on power-up, self-tests can also be
initiated from the test menu. These tests check most of the analog and digital
signal generation circuitry in the DS345. Pressing any UNITS key when the
SELF-TEST menu item is displayed starts the self-tests. The tests take about
three seconds to execute, and should end with the display "test pass". If the
self-test encounters a problem it will immediately stop and display a warning
message. See the
TROUBLESHOOTING
section for a list and explanation of
the error messages. If the DS345 fails any test it still may be operated, sim-
ply press any key to erase the error message.
note:
the error "Gain FS Err" can occur if a signal is applied to the external
AM input during self-test. Disconnect any signals at this input during self-test.
The DS345 tests its CPU and data memory, ROM program memory, calibra-
tion constant integrity, ASIC waveform memory, modulation program memo-
ry, 12-bit waveform DAC, analog-to-digital converter, output amplifier, offset
and amplitude control circuits, frequency doubler, and square wave compara-
tor.
Items
not
tested are the connections from the PC boards to the BNC connec-
tors, the output attenuators, the 40 MHz clock and phase locking circuitry, the
computer interfaces, and the SYNC output driver.
AUTOCAL
The DS345's autocal routine calibrates the majority of the signal generation
path, including the DC offsets of the output amplifier, the signal path offsets,
the offset and gain of the amplitude controls, and the gain of the output am-
plifier. These calibrations correct for any aging and temperature dependen-
cies of the DS345's circuits. Pressing any UNITS key when the AUTOCAL
menu item is displayed starts the calibration. Autocal is disabled during the
first two minutes after power on to allow the DS345 to warm up (an error will
be displayed if autocal is started before this time).
Autocal takes about two minutes to execute and should end with the mes-
sage "cal done".
note:
Be sure to have disconnected any signals from the
External AM input during Autocal. If AUTOCAL encounters a problem it will
immediately stop and display an error message. See the
TROUBLESHOOT-
ING
section (pg. 4-1) for a list and explanation of the error messages. If the
DS345 fails its AUTOCAL it still may be operated, simply press any key to
erase the error message. However, the error may be indicating a hardware
problem that probably should be addressed.
The items
not
calibrated by the autocal procedure are the frequency depen-
dent amplitude corrections, the doubler carrier null, the attenuator ratios, and
the clock frequency. These values are stable and should not need adjust-
ment except during an annual recalibration.
note:
Disconnect any signals from the External AM input during Autocal