Stanford Research Systems SR620, Manual

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32 Programming Commands
SR620 Universal Time Interval Counter
synchronizing of the measurements with the
returned answers.
DREL (?) j
The DREL command sets the display rel and is
equivalent to the front panel "SET REL" button.
The parameter j = 1 sets the REL, j = 0 clears the
REL, and j = 2 clears the REL and the results of
the last measurement, j =3 sets the REL to the
current cursor position.
COMP
The COMP command changes the arming parity
in ± time arming mode. This command is the same
as toggling the state of the front panel COMPL
LED.
GATE (?) x
The GATE command sets the width of the
frequency, period, or count gate to x. The gate
width x may range from 1ms to 500s in a 1,2,5
sequence. If the value x is negative the gate is set
to an externally triggered gate of width x. If the
measurement mode or arming mode do not
support gates an error occurs.
JTTR (?) j
The JTTR command sets the type of jitter
calculation. The parameter j = 0 sets standard
deviation calculation while j = 1 sets Allan
variance. It should be noted that the jitter type is a
property of the present mode and that if the mode
is changed the jitter type may also change.
MODE (?) j
The MODE command sets the instrument
measurement mode according to the following
table:
j mode
0
time
1 width
2 rise/fall time
3 frequency
4 period
5 phase
6 count
Note : after setting the SR620's mode the other
measurement parameters should be set to their
desired values because changing modes may
cause them to change.
SIZE (?) x
The SIZE command sets the number of samples
in a measurement. The parameter x may be
between 1 and 10^6 in a 1,2,5 sequence. The
SIZE? query returns a floating point number with
one significant digit.
SRCE (?) j
The SRCE command sets the source of the
measurement. The parameter j = 0 set the source
to A, j = 1 sets the source to B, and j = 2 sets the
source to REF. Additionally, in frequency, period,
and count modes j = 3 sets the source to ratio
(A/B). In phase mode the source is fixed and may
not be set while in rise/fall time REF may not be
selected as the source.
STRT
The STRT command is equivalent to pushing the
front panel START button.
STOP
The STOP command resets the present
measurement and is the same as pressing the
"RESET" button on the front panel.
Data Transmission Commands
MEAS? j
The MEAS? query starts a measurement and
returns the result when the measurement is
complete. The parameter j selects which statistic
is to be returned.
j statistic
0
mean
1 jitter
2 max
3 min
This command always returns the value of the
next complete measurement. Thus, if a
measurement is in progress the command will
return the value of the present measurement when
it is done, not a new measurement. It is
recommended that automeasure be off when
using this command to ensure that the result