Stanford Research Systems SR620, Руководство пользователя

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Calibration Procedure 71
SR620 Universal Time Interval Counter
4) Set the slope to - and calbyte 12 (13,11) to
1800.
5) Slowly increase the value of calbyte 12 (13,11)
until the trigger light flashes. This is the correct
value.
Input Threshold Gain Calibration
1) Set the slope to + and the threshold to 4.5V.
Set calbyte 6 (7,5) to 1. Attach a precision dc
source to input A. Slowly increase the dc
voltage from 0 until the trigger light flashes.
2) The gain factor is dc voltage/4.5.
3)
Calculate the value of calbyte 6 (7,5) as
follows:
a) If the gain is less than 1 multiply the gain
factor by 65536 and round the answer even.
b) If the gain factor is greater than or equal to
1 multiply the gain factor by 65536 and round
the answer odd.
4) Enter the new calbyte value.
Autolevel Offset Calibration (For A and B only)
1) With the input open, turn the threshold knob to
the autolevel position and read the trigger
level.
2) Divide the trigger level by 0.00488
3) Add this value to the calbyte.
Clock Oscillator Calibration
Note : Allow at least 1 hour warmup before
adjusting the clock.
1) Attach a scope probe to TP1 ( R305) in the
right rear of the circuit board. Set the scope to
50mV/div and 20ns/div.
2) Adjust L303,L304,L306,L307 for maximum
amplitude of the 90MHz clock signal.
3) Run Autocal.
4) Attach a precision 10MHz source to the A
input and measure its frequency with a 1s
gate. Adjust calbyte 4 until the display reads
exactly 10.0MHz. The allowable range of
calbyte 4 is 0 to 4095 all other numbers are
set modulo 4096. If the frequency of the oven
oscillator cannot be set with a calbyte in this
range, set the calbyte to midrange (2048) and
adjust the coarse adjustment screw on the
oscillator until the frequency is correct.
Insertion Delay Calibration
Start this procedure by running AutoCal on a well
warmed-up instrument.
Note : If the calbytes calculated below are positive
set the calbyte to that value. If they are negative
set them to 65536 - abs(value) . Use the scope
histogram display to see measurement values
when adjusting the Calbytes.
Time Mode:
1) Set the mode to time, arming to +time,source
to A, sample size to 1000, and the triggers to
the midpoint of the input signals.
2) Tee the output of the pulse generator to the A
and B inputs with equal length cables.
Terminate the inputs with 50 Ohms.
3) Set the A and B slopes to + and measure the
time interval. Adjust calbyte 28 until the
answer reads 0.
4) Set the A and B slopes to - and measure the
time interval. Adjust calbyte 31 until the
answer reads 0.
5) Attach the non-inverting output of the power
splitter to A and the inverting output to B.
6) Set the A slope to + and the B slope to - and
measure the time interval. Adjust calbyte 29
until the answer reads 0.
7) Set the A slope to - and the B slope to + and
measure the time interval. Adjust calbyte 30
until the answer reads 0.
8) Set the Source to B.
9) Set the A and B slopes to + and measure the
time interval. Adjust calbyte 36 until the
answer reads 0.
10) Set the A and B slopes to - and measure the
time interval. Adjust calbyte 39 until the
answer reads 0.
11) Attach the non-inverting output of the power
splitter to A and the inverting output to B.