Stanford Research Systems DS345, Manual

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Calibration
6-4
DS345 has had at least 1/2 hour to warm up.
2) Set calbyte number 0 to 2980. For a unit with an optional oscillator set
SW300 switch 1 (bottom board) to OFF.
3) Adjust L203 (top board) so that the output U205 pin 6 is closest to 0 V DC.
Adjust L204 (top board) so that the oscillator frequency is within 1 Hz of 10.0
MHz.
if the unit has an optional oscillator:
4) Set SW300 switch 1 to ON. Set calbyte 0 to 2048.
5) If necessary, adjust the optional oscillator coarse adjustment screw so that
the frequency is within 1 Hz of 10 MHz.
Output Amplifier Bandwidth
These adjustments correct the bandwidth of the output amplifier. A complete
calibration must be performed if these adjustments are changed. All of the
adjustments are on the bottom PCB and may be reached through holes in
the shield. Use an insulated adjusting screwdriver.
1) Set the DS345 for square wave, 8 Vpp, 10 kHz. Measure the DC voltage
at the output of U600 pin 6. Adjust P600 to until this voltage is 0.0V.
2) Connect the output of the DS345 to the oscilloscope with a 50
Ω
termina-
tor. Set the DS345 to square wave, 8 Vpp, 100 Hz. Set the scope to 2 V/div
vertical and 5 ms/div horizontal. Adjust R639 for the squarest output wave-
form.
3) Set the DS345 to 500 kHz. Set the scope to 1
µ
s/div. Adjust P601 for the
squarest output waveform.
4) Set the scope to 200ns/div. Adjust C611 for the fastest output risetime
without excessive overshoots.
5) Do a complete calibration of the DS345
Bessel Filter Adjustment
This adjustment sets the bandpass of the DS345's Bessel waveform filter.
The adjustments are on the top board. Run autocal after these adjustments.
1) Press [SHIFT][DEFAULTS]. This will recall the DS345's default arbitrary
waveform- a square wave. Set the DS345 to ARB waveform, 8 Vpp, 2 MHz
sampling frequency. Connect the DS345's output to an oscilloscope with a
50
Ω
terminator. Set the scope to 2 V/div vertical and 200 ns/div horizontal.
2) Starting with C645, adjust C645, C644,C643, and C642 to make the out-
put rise time as fast as possible while minimizing the peak-to-peak ripple.
Several iterations of the capacitors may be needed to acheive optimum re-
sponse.
3) Run autocal.