Stanford Research Systems SR620, Руководство пользователя

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Calibration Procedure 69
SR620 Universal Time Interval Counter
CALIBRATION
The SR620 is calibrated by adjusting calibration
constants which are stored in the unit's battery-
backed up RAM. The calibration values which
were determined when the unit was manufactured
are stored in the unit's ROM, and may be recalled
at any time.
The SR620 is mostly self-calibrating. The AutoCal
procedure may be run to adjust most of the
calibration constants to their correct value. An
important exception to this is the adjustment of the
10 MHz timebase. (See calibration procedure for
adjusting timebase frequency.) To run the AutoCal
procedure, select the "Autocal" line in the CAL
submenu of the CONFIG menu and push the
"START" button. The procedure will finish (in
about two minutes) with the message "Cal done".
(See the troubleshooting section of the manual if a
error occurs.) Autocal should be run every 1000
operating hours, or if the environmental operating
conditions change significantly. It may also be run
before critical measurements to insure optimum
instrument performance.
CALBYTES
The calbytes adjust for unit-to-unit variations which
are very stable. Most of the calibration is
automatic; there are only a few manual calibration
procedures. The calbytes may be viewed (and
adjusted) by putting the "cal enable" jumper
(inside the SR620 at the front center of the circuit
board) into the "enable" position and then looking
at the "Caldat" line in the Cal submenu. The
function of the calbytes are given in the table here:
Calbyte Function
0
Start TAC gain adjust
1 Start TAC zero offset
2 Stop TAC gain adjust
3 Stop TAC zero offset
4
10MHz oscillator adjustment
5,6,7
Ext,A,B comparator gain adjustment
8,9,10 Ext,A,B positive slope zero offset
adjust
11,12,13 Ext,A,B negative slope zero offset
adjust
14,15 A,B autolevel offset adjust
16
D/A #0 zero offset adjust
17 D/A #1 zero offset adjust
18 D/A #0 gain adjust
19 D/A #1 gain adjust
20 DVM input #0 20V range zero offset
21 DVM input #1 20V range zero offset
22 DVM #0 zero offset for 2V range
23 DVM #1 zero offset for 2V range
24 DVM #0 20V range gain adjust
25 DVM #1 20V range gain adjust
26 DVM #0 2V range gain adjust
27 DVM #1 2V range gain adjust
28-39 Insertion delay correction (total
correction = base (correction)
for inputs and slopes A+B+,A+B-,A-
B+,A-B-,REF+B+,REF+B-,REF-B+,
REF-B-,B+A+,B-A+,B+A-,B-A-
40 Base insertion delay
41-45 Width insertion delay correction ( total
correction = base (byte 40) +
correction) for inputs and slopes A+,A-
,B+,B-,REF
46-49 Tr/tf insertion delay correction (total
correction = base (byte 40) +
correction) for inputs and slopes A+,A-
,B+,B-
50 Freq/period insertion delay
51-115 Start TAC linearization bytes
116-180 Stop TAC linearization bytes