Sub-Sampling Remarks - Agilent Technologies 3458A User Manual

Sub-Sampling
Remarks
•
For sub-sampling, the trigger event and sample event requirements are
ignored (these events are discussed in Chapter 4). The only triggering
events that apply to sub-sampling are the trigger arm event (TARM
command) and the sync source event (SSRC command).
•
You cannot use the NRDGS command for sub-sampling. You must use the
SWEEP command to specify the number of samples and the
effective_interval. The minimum effective_interval for sub-sampling is 10
nanoseconds. The maximum rate at which samples arc taken is 50k samples
per second (20µs between samples).
•
You cannot use autorange for sub-sampled measurements; you must
specify the range as the first parameter of the SSAC or SSDC command
(max._input parameter). The max._input parameters and the ranges they
select are:
max._ input Parameter Selects Range Full Scale
0 to .012
>.012 to .120
>.120 to 1.2
>1.2 to 12
>12 to 120
>120 to lE3
As with direct sampling, you can specify a level triggering voltage up to
500% of the range. The required SINT format, however, cannot handle
samples greater then 120% of range.
•
If reading memory is disabled when you execute the SSAC or SSDC
command, the multimeter automatically sets the output format to SINT (the
memory format is not changed). Later, when you change to another
measurement function, the output format returns to that previously
specified. You must use the SINT output format when sub-sampling and
outputting samples directly to the GPIB. You can however, use any output
format if the samples are first placed in reading memory (see next remark).
To do this, you should enable reading memory before executing the SSAC
or SSDC command (executing SSAC or SSDC does not change the output
format to SINT when reading memory is enabled).
•
When sub-sampling with reading memory is enabled, reading memory
must be in FIFO mode, must be empty (executing MEM FIFO clears
reading memory), and the memory format must be SINT prior to the
occurrence of the trigger arm event. If not, the multimeter generates the
SETTINGS CONFLICT error when the trigger arm event occurs and no
samples are taken.
•
When sub-sampling an input signal with a frequency content ³ 1MHz, the
first sample may be in error because of interpolator settling time. To ensure
the first sample is accurate, insert a 500ns delay using the DELAY 500E-9
command. (When sub-sampling, the delay is inserted between the sync
10mV 12mV
100mV 120mV
1V 1.2V
10V 12V
100V 120V
1000V 1050V
Chapter 5 Digitizing 143