Keysight Technologies 3458A Guide D'utilisation page 215

Digitizing 5
Sending samples to the controller
When samples are sent directly to the controller, an algorithm must be used to
re-order the samples and produce the composite waveform. The SSPARM?
command returns three parameters for the algorithm. The first parameter
returned is the number of bursts measured that contained N samples. The second
parameter returned is the number of bursts measured that contained N-1
samples. The third parameter returned is the value of N. For example, assume you
are sub-sampling a 10 kHz signal and specify 22 samples with an
effective_interval of 5 µs. In this example, the multimeter takes 2 bursts
containing 6 samples each and 2 bursts containing 5 samples each. Each burst is
delayed 5 µs from the previous burst. The values returned by SSPARM? are then 2,
2, and 6.
When sub-sampling, the maximum sample rate is 50k samples per second
regardless of the specified effective_interval. (If you specify an effective_interval of
≥20 µs, the multimeter is no longer sub-sampling but direct-sampling.) When
sending samples directly to the controller (using the required SINT format which is
2-bytes per sample) the GPIB/controller must be able to handle the data at a
maximum rate of 100k-bytes per second. If not, the multimeter generates the
TRIGGER TOO FAST error.
In the program on the following page, the SSAC command is used to digitize a 10
kHz signal with a peak value of 5 V. The SWEEP command instructs the
multimeter to take 1000 samples (Num_samples variable) with a 2 µs
effective_interval (Eff_int variable). The measurement uses the default level
triggering for the sync source event (trigger from input signal, 0%. AC-coupling,
positive slope). Line 110 generates a SYN event and transfers the samples directly
to the computer. Lines 230 through 400 sort the sub-sampled data to produce the
composite waveform. The composite waveform is stored in the Wave_form array.
10OPTION BASE 1!COMPUTER ARRAY NUMBERING STARTS AT 1
20INTEGER Num_samples,Inc,I,J,K,L!DECLARE VARIABLES
30Num_samples=1000!DESIGNATE NUMBER OF SAMPLES
40Eff_int=2.0E-6!DESIGNATE EFFECTIVE INTERVAL
50INTEGER Int_samp(1:1000) BUFFER!CREATE INTEGER BUFFER
60ALLOCATE REAL Wave_form(1:Num_samples) !CREATE ARRAY FOR SORTED DATA
70ALLOCATE REAL Samp(1:Num_samples)!CREATE ARRAY FOR SAMPLES
80ASSIGN @Dvm TO 722!ASSIGN MULTIMETER ADDRESS
Keysight 3458A User's Guide 215