LeCroy LSA1000, Руководство оператора

Страница: 19 / 115

2 – 5
Capture
In addition to the primary specifications and three parameters
described above, capture techniques, the triggering system,
channels and ADC specification all impact on LSA1000
performance.
Acquisition Technique
Single-shot acquisition is t
he LSA1000’s basic acquisition technique,
which makes the instrument very suitable for the study of signal
phenomena that have a low-repetition rate or are not repeated
—
hence single- shot.
An acquired waveform consists of a series of measured voltage
values sampled at a uniform rate on the input signal. The acquisition
is typically stopped at a fixed time after the arrival of a trigger event
as determined by the trigger delay. The acquisition consists of a
single series of measured data values associated with one trigger
event. The time of the trigger event is measured using the timebase
clock. The timing information of a waveform is determined using the
trigger event as the definition of time 0. Since each channel has its
own ADC, the voltage on each of the input channels is sampled and
measured at the same instant. This allows extremely reliable time
measurements between channels.
Trigger delay can be selected anywhere within a range that allows
the waveform to be sampled from well before the trigger event up to
the moment it occurs (100% pretrigger), or at a time starting at the
equivalent of 1,000 times of the memory size after the trigger.
The captured input data signal is transferred to memory for
measurement and analysis.
Analog – Digital Conversion
High-speed LSA1000 performance is made possible by the use of
advanced flash ADCs whose vertical resolution guarantee a clear
representation of the signal. These ADCs measure the voltage level
at evenly spaced intervals and store the digitized value in high-speed
dedicated memory. The shorter the intervals, the faster the digitizing
rate
— and the finer the time structure able to be seen. The higher
the resolution of the ADC, the better its sensitivity to small voltage
changes. And the greater its memory capacity, the longer the
recording time available.