Stanford Research Systems SR830, Manual

Page: 98 / 177

5-15
Remote Programming
DATA TRANSFER COMMANDS
OUTP ? i The OUTP? i command reads the value of X, Y, R or
θ
. The parameter
i selects X (i=1), Y (i=2), R (i=3) or
θ
(i=4). Values are returned as ASCII
floating point numbers with units of Volts or degrees. For example, the
response might be "-1.01026". This command is a query only command.
OUTR ? i The OUTR? i command reads the value of the CH1 or CH2 display.
The parameter i selects the display (i=1 or 2). Values are returned as
ASCII floating point numbers with units of the display. For example, the
response might be "-1.01026". This command is a query only command.
SNAP ? i,j {,k,l,m,n} The SNAP? command records the values of either 2, 3, 4, 5 or 6 param-
eters at a single instant. For example, SNAP? is a way to query values of
X and Y (or R and
θ
) which are taken at the same time. This is important
when the time constant is very short. Using the OUTP? or OUTR? com-
mands will result in time delays, which may be greater than the time con-
stant, between reading X and Y (or R and
θ
).
The SNAP? command requires at least two parameters 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
4
θ
5 Aux In 1
6 Aux In 2
7 Aux In 3
8 Aux In 4
9 Reference Frequency
10 CH1 display
11 CH2 display
The requested values are returned in a single string with the values sep-
arated by commas and in the order in which they were requested. For
example, the SNAP?1,2,9,5 will return the values of X, Y, Freq and
Aux In 1. These values will be returned in a single string such as
"0.951359,0.0253297,1000.00,1.234".
The first value is X, the second is Y, the third is f, and the fourth is
Aux In 1.
The values of X and Y are recorded at a single instant. The values of R
and
θ
are also recorded at a single instant. Thus reading X,Y OR R,
θ
yields a coherent snapshot of the output signal. If X,Y,R and
θ
are all
read, then the values of X,Y are recorded approximately 10µs apart from
R,
θ
. Thus, the values of X and Y may not yield the exact values of R and
θ
from a single SNAP? query.
The values of the Aux Inputs may have an uncertainty of up to 32µs. The
frequency is computed only every other period or 40 ms, whichever is
longer.