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1、? ? 7LPHEDVH?0RGHV?DQG?6HWXS 7LPHEDVH?6DPSOLQJ?0RGHV Depending on the timebase, any of three sampling modes can be chosen: Single-Shot, Random Interleaved Sampling (RIS) or Roll Mode. Furthermore, for timebases suitable for either Single-Shot or Roll Mode, the acquisition memory can be subdivided in
2、to user-defined segments to give Sequence Mode. Channels can also be combined to boost sample rate and record length. 6LQJOH?6KRWSingle-Shot is the digital oscilloscopes basic acquisition technique and other timebase modes make use it. An acquired waveform consists of a series of measured voltage va
3、lues sampled at a uniform rate on the input signal. The acquisition, a single series of measured data values associated with one trigger event, is typically stopped at a fixed time after the arrival of the event, this being determined by the trigger delay. The time of the trigger event is measured u
4、sing the timebase clock. The horizontal position of a waveform is determined using the trigger event as the definition of time zero. Waveform display is also carried out using this definition. Because each channel has its own ADC, the voltage on each input channel is sampled and measured at the same
5、 instant. This allows very reliable time measurements between different 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 % pre-trigger), or at the equivalent of 10 000 divisions (
6、at the current time/div) after the trigger. For fast timebase settings the ADCs maximum single-shot sampling rate is used (on one and each channel, with higher sampling rates achieved by combining channels see page 74). For slower timebases, the sampling rate is decreased and the number of data samp
7、les maintained. (See Appendix A for details). RadioFans.CN 收音机爱 好者资料库 ? 7LPHEDVH?0RGHV?DQG?6HWXS When using slow timebases, sample-rate decreases and very short events such as glitches can be missed if they occur between two samples. To prevent this, a special circuitry called the Peak Detect system
8、 can be switched on (see “Channel Use” menu, page 75) to capture the signal envelope with a resolution of 2.5 ns. This is done without destroying the underlying, simultaneously captured data, on which a wide range of advanced processing can be performed. RIS is an acquisition technique that allows e
9、ffective sampling rates higher than the maximum single-shot sampling rate. It is used on repetitive waveforms with a stable trigger. The maximum effective sampling rate of 10 GS/s can be achieved by acquiring 100 single-shot acquisitions, or bins, at 100 MS/s using the 9304C, 9310C, 9314C Series osc
10、illoscopes; 20 bins at 500 MS/s when using the other models. These bins are positioned approximately 0.1 ns apart. The process of acquiring this number of bins and satisfying the time constraint is random. The relative time between ADC sampling instants and the event trigger provides the necessary v
11、ariation, measured by the timebase to 10 ps accuracy. 3HDN?HWHFW NOT AVAILABLE WITH 9304C, 9310C, 9314C SERIES 5,6?5DQGRP?,QWHUOHDYHG 6DPSOLQJ RadioFans.CN 收音机爱 好者资料库 ? On average, 104 trigger events are needed to complete an acquisition. But sometimes many more are needed. These segments are interl
12、eaved to provide a waveform covering a time interval that is a multiple of the maximum single-shot sampling rate. However, the real-time interval over which the waveform data are collected is orders of magnitude longer and depends on the trigger rate and the desired level of interleaving. The oscill
13、oscope is capable of acquiring approximately 40 000 RIS segments per second. 5ROOSingle-shot acquisitions at timebase settings slower than 0.5 s/div (10 s/div for traces with more than 50 000 points) have a sufficiently low data rate to allow the display of the incoming points in real time. The osci
14、lloscope shows the incoming data continuously, “rolling” it across the screen, until a trigger event is detected and the acquisition completed. The latest data is used to update the trace display in the same manner as a strip-chart recorder. Waveform Math and Parameter calculations are done on the c
15、ompleted waveforms. 6HTXHQFHSequence Mode is an alternative to single-shot acquisition that offers many unique features. The complete waveform consists of a number of fixed-size segments acquired in Single-Shot Mode (see Appendix A for the limits), which are able to be selected. . The dead time betw
16、een the trigger events for consecutive segments can be kept to under 50 s in contrast to the hundreds of milliseconds normally found between consecutive single-shot waveforms. Complicated sequences of events covering a large time interval can be captured in fine detail, ignoring uninteresting period
17、s between events. And time measurements can be made between events on different 1RWH? to ensure low deadtime between segments, button- pushing and knob-turning is to be avoided during sequence acquisition. 1RWH? The behavior of , , and is modified in Roll Mode and Sequence Modes (refer to previous c
18、hapter and pages 78 and 79). RadioFans.CN 收音机爱 好者资料库 ? 7LPHEDVH?0RGHV?DQG?6HWXS segments of a sequence waveform using the full precision of the acquisition timebase. Trigger-time stamps are given for each of the segments in the “Text 7(51$/ appears when an External clock mode is chosen. 6DPSOLQJ Thi
19、s menu is inactive when the external sample clock is being used. Only single-shot acquisition is available (see below). 6DPSOH? if the time between two consecutive triggers exceeds a time-out that can be selected, the acquisition will stop. 0D?VHJPHQW To select using the corresponding button or associated knob the maximum record length for each segment. See Appendix A for model maximums. 1RWH? A summary of the acquisition conditions is displayed above the “TIMEBASE” menus, indicating number of segments, available record length per segment, sampling rate, and timebase setting.
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