Stanford Research Systems SR865A, Operation Manual

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Chapter 4 Programming 141
SR865A DSP Lock-in Amplifier
STREAMCH?
Returns the stream configuration i
STREAMRATEMAX?
The STREAMRATEMAX? query returns the maximum allowed streaming rate (at the
current time constant and sync filter period) in Hz. This is a query only command.
The streaming rate sets how often data points are streamed to the ethernet interface. All
streamed parameters are sampled at the same rate (and at the same times).The maximum
streaming rate is determined by the time constant of the SR865A. Shorter time constants
allow faster streaming rates, and if sync filter is on, shorter sync filter periods allow faster
streaming rates, up to a limit of 1.25 MHz. The actual streaming rate can be set to the
maximum allowed rate divided by factors of 2.
Example
STREAMRATEMAX? Returns the maximum streaming rate in Hz
STREAMRATE(?) { n }
The STREAMRATE n command sets the streaming rate to the maximum rate divided by
2
n
. The value of n is limited to 0 ≤ n ≤ 20. Set n=0 for the maximum streaming rate.
For example, if
STREAMRATEMAX?
returns 78125, then
STREAMRATE 4
will set the
streaming rate to (78125)/(2
4
) = 4882.8125 Hz.
The STREAMRATE? query returns the value n.
Example
STREAMRATE 4 Sets the streaming rate to the max rate divided by 2
4
STREAMRATE?
Returns the streaming rate n
STREAMFMT(?) { i }
The STREAMFMT i command sets the stream data format to float32 (i=0) or int16 (i=1).
Float32 requires 4 bytes per data point and int16 requires 2 bytes per point. Float32 will
use twice the ethernet bandwidth at the same streaming rate as int16.
Int16 values range from − 32768 to +32767. Full-scale values (corresponding to
Sensitivity, divided by any expand) are returned as the integer 29491 (90% of 32768).
Example
STREAMFMT 0 Sets the streaming format to float32 (4 bytes per point)
STREAMFMT?
Returns the streaming format i
STREAMPCKT(?) { i }
The
STREAMPCKT i
command sets the ethernet stream packet size to 1024 (i=0), 512
(i=1), 256 (i=2) or 128 (i=3) bytes.
Example
STREAMPCKT 0 Sets the ethernet streaming packet size to 1024 bytes