Stanford Research Systems SR844, User Manual

Page: 127 / 246

Data Transfer 4-25
SR844 RF Lock-In Amplifier
Data Transfer Commands
OUTP? i
The
OUTP? i
command reads the value of X, Y, R or
θ
. The parameter
i
selects
X (
1
), Y (
2
), R [V] (
3
), R [dBm] (
4
) or
θ
(
5
). Values are returned as ASCII
floating point numbers with units of Volts, dBm or degrees. The units are not part
of the returned string. For example, the response might be
-1.0103E-6
. This
command is a query only command.
Important!
The returned value does have Offsets and Ratio applied. However, Expand is not
applied (compare
OUTR?ch
below).
OUTR? ch
The
OUTR? i
command reads the value of the CH1 or CH2 display. The
parameter ch selects the display (
ch=1
or
ch=2
). Values are returned as ASCII
floating point numbers with units of the display. For example the response might
be
-1.0103E-6
. This command is a query only command.
The response has Ratio, Offset and Expand applied, just like the display.
SNAP? i,j
{,k,l,m,n}
The
SNAP?
command returns the values of up to six parameters at a single
instant. For example,
SNAP?
is a way to query values of X and Y (or R and
θ
)
recorded at the same instant. This is important when the time constant is very
short. Using the
OUTP?
or
OUTR?
command will result in time delays between
reading X and Y (or R and
θ
) which may be greater than the time constant,.
The
SNAP?
command requires at least two and at most six parameters. The
parameters
i,j,k,l,m,n
select the parameters below.
i, j, k, l, m, n parameter
1 X
2 Y
3 R [V]
4 R [dBm]
5
θ
6 AUX IN 1
7 AUX IN 2
8 Reference Frequency
9 CH1 display
10 CH2 display
The requested values are returned in a single ASCII string with the values in the
order requested, separated by commas. For example, the
SNAP?1,2,8,6
will
return the values of X, Y, Freq, and AUX IN 1. These values will be returned in a
single string such as
0.9514E–3,–1.2271E-5,2.770E7,-3.219
The first value is X [V], the second is Y [V], the third is F
REF
[Hz] and the last is
AUX IN 1 [V].