Stanford Research Systems DG535, Operation And Service Manual

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21
Output Offset Calibration
This procedure is used to calibrate the offset of
the front panel output drivers. You will adjust
calibration values to get zero offset into a high
impedance load on the T0, A, B, AB, -AB, C, D,
CD and the -CD outputs.
___ Recall default settings: RECALL 0
EXC
___ Use the TRIG Menu key to select Int
trigger. Press TRIG again to set the rate
to 100 KHz.
___ Use the DELAY Menu key to set the
delays for channel B and channel D to 5
µs.
___ Use the OUTPUT Menu key to set all
the outputs for High-Z loads, NIM logic
levels (between 0 and -0.8 VDC). Do
this for T0, A, B, AB, C, D and CD
outputs.
For each of the outputs T0, A, B, AB, -AB, C,
D, CD and -CD:
___ Connect the output to the oscilloscope
input (1 M
Ω input, 200 mV/div
sensitivity ).
___ Hold down the BSP key and press the
OUTPUT key to access the Offset
calibration value for the corresponding
channel.
___ Use the Up/Down cursor keys to adjust
the offset of the output ( i.e. the top of
the -0.800 V pulse ) to zero.
Jitter Calibration
This procedure is used to minimize the timing
jitter of all the outputs with respect to an
external trigger. Apply a fast risetime ( <3 ns )
+2 V pulse with a 10 KHz repetition rate to
External Trigger input of the DG535 under test.
The same pulse should also go to the CH 1 input
of the oscilloscope. A good way to do this is to
use the T0 output from another DG535, which
has been set to drive a 50
Ω load to TTL levels.
Place a tee directly on this output, with one
cable to the DG535 under test, and the other
cable to the oscilloscope. Both cables should be
terminated into 50
Ω . With this arrangement the
T0 output sees a 25
Ω load, and so the pulse
amplitude will be 2 V.
The jitter from the External Trigger input to any
output (T0, A, B, C or D) should be less than 50 ps
rms. On a non-intensified fast oscilloscope triggered
at 10 KHz, a 50 ps rms jitter will appear as about
200 ps peak-to-peak jitter. Careful attention to
trigger levels and termination impedances is
required to observe this small jitter.
DG535 settings:
___ Recall default settings with RECALL 0
EXC
___ Select Ext trigger: +1.00 V threshold,
+ slope, 50
Ω Term
___ Set Delay A = 100 ns, B, C, D to 1 µs
___ Connect the A output to the oscilloscope's
CH 2 input
Scope settings:
___ CH 1 and CH 2 inputs both terminated into
50
Ω
___ Trigger on CH 1 with trigger threshold set
to +1.00 V
___ 500 mV/div sensitivity on both channels.
___ Main timebase set for 50 ns/div
___ Delayed timebase set for 5 ns/div
___ Center CH 2 trace and horizontal expand
x10 to 500 ps/div
___ Change CH 2 sensitivity to 200 mV/div
Jitter Cal Factor
___ Hold down the BSP key and press the TRIG
key to access the Jitter Cal factor.
___ Adjust the Jitter Cal factor to minimize the
jitter from the External trigger to the A
delay output.
Delay Cal Factors
For each of the channels T0, B, C and D (not A):
___ Set the delay for the selected channel to
100 ns, all other delays to 1 µs. ( Skip this
step for T0 )
___ Connect the selected delay to the CH 2
input of the oscilloscope.
___ Hold down the BSP key and press the
DELAY key to access the delay factor for
the corresponding delay output.
___ Adjust the delay factor to minimize the jitter
between the External trigger and the delay
output