lecroy 93XXC-OM-E12 电路图.pdf

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1、? =RRP?0DWKHPDWLFV?DQG?0DWK?6HWXS ? =RRPLQJ?IRU?3UHFLVH?:DYHIRUP?0HDVXUHPHQWV Several traces can be zoomed from a single waveform to obtain precise timing measurements. For instance, on a waveform composed of two pulses separated by a long delay, Trace A could be made a zoom of the first pulse, and

2、Trace B a zoom of the second. The combination of long memory and zooming allows extremely accurate time interval measurements. And the time resolution on the viewed trace can be significantly improved. For example, choosing 50 000 points per channel on a timebase of 0.1 ms/div, traces can be expande

3、d to as much as 50 ns/div a factor of 2000. Using Relative Time cursors (see Chapter 14), a delay of, say, 500 s could be measured with resolution as high as 0.5 ns. Even with as many as eight million points acquired, zooming can be done until there are only a few points on the screen. 8VLQJ?0XOWL?=

4、RRPWith Multi-Zoom, the zoomed region of the waveform can be moved simultaneously along two or more different traces, or two or more regions of the same trace. When “Multi-Zoom” “On” is selected from the “ZOOM MATH” menu (see page 106), the horizontal zoom and position controls apply simultaneously

5、to all displayed traces A, B, C and D allowing similar sections of different traces to be viewed at the same time. The vertical controls still act individually on the traces: switching from one trace to another is done using the TRACE ON/OFF buttons. The highlighting of trace titles in the Displayed

6、 Trace label indicates an active Multi-Zoom. =RRPLQJ?0DWK?)XQFWLRQVWhen Trace A, B, C or D is defined as a mathematical function rather than as a simple zoom (see next section), the zoom controls remain operative and defining another trace as a zoom of the math function becomes unnecessary. In order

7、 to view the entire mathematical function, simply cancel any expansion or position change by pressing RESET. RadioFans.CN 收音机爱 好者资料库 ? =RRP?0DWKHPDWLFV?DQG?0DWK?6HWXS 0DWK?)XQFWLRQV?DQG?2SWLRQV A wide range of standard or optional mathematical and waveform processing functions are available. The sco

8、pes standard waveform mathematics functions consist of waveform negation, identity, addition, subtraction, multiplication and division, summed averaging of up to 1000 waveforms and the (sin x)/x interpolation function. Advanced waveform processing features, depending on the options installed, includ

9、e: ? Continuous Averaging (menus page 109); ? Summed Averaging of up to 1 000 000 waveforms (menus 109); ? Enhanced Resolution by up to 3 bits with filtering (menus 1010); ? Extrema envelope of many waveforms (menus 1011); ? Fast Fourier Transform, including FFT averaging (menus 1012 and 1013); ? Ma

10、thematical Functions such as Integral, Derivative, Logarithm, Exponential, Square, and Square Root (menus 1014); ? Parameter Analysis, histogramming, trending and statistical analysis (menus page 1015). Trace B defined as the average of A, and Trace C made the integral of B thus displaying the integ

11、ral of the averaged difference between Channels 1 and 2. In order to avoid slowing down the instrument with unwanted computations, a particular mathematical function is only computed when its display is turned on. However, using the same example as above, it would be sufficient to display Trace C al

12、one, as the instrument knows it must compute A and B as intermediate steps to C. Waveform processing can also take time when many data points are involved. This delay can be cut by limiting the number of data points used in the computation. To do this, the instrument will process the entire waveform

13、 by taking every Nth point, where N depends on the timebase and the desired maximum number of points, and the first point taken is always the data value at the left-hand edge of the screen. &RPELQLQJ?&KDQQHOVZoom and math functions on Traces A, B, C, D and Reference Memories M1, M2, M3, M4 use the i

14、nstruments system memory, which is dynamically allocated to each trace as required. When more acquisition memory is achieved by combining channels, a single long trace can consume all the reference memory or zoom and math trace capacity in the instrument. When this happens, an on-screen warning mess

15、age will avert accidental storing of a new trace to a reference memory already in use. 1RWH? A processing title for each displayed trace will be shown in the Displayed Trace Label. If the title is missing, the desired processing cannot be done and the contents of the trace remain unchanged. ? =RRP?0

16、DWKHPDWLFV?DQG?0DWK?6HWXS &RQILJXULQJ?IRU?=RRP?DQG?0DWK Press to enable the configuration of any of the four traces and execute any zoom, math function using the “ZOOM + MATH” menus. Any trace and function can be chained to another trace and function (not all functions shown are necessarily availabl

17、e). Trace A, for example, could be configured to average Channel 1, Trace B could be made a Fourier Transform (FFT) of A, and Trace C a zoom of B. All traces can be viewed simultaneously on-screen using the ZOOM + MATH TRACE ON/OFF buttons. Any function can be zoomed directly. 5(),1(?$?%?&?RU? To se

18、lect the trace to be redefined and accesses the “SETUP” menus (described in the remainder of this chapter, using A as an example). 0XOWL?=RRP For switching Multi-Zoom “On” or “Off”. When “On”, all displayed traces (A,B,C,D) are simultaneously controlled by the horizontal POSITION and ZOOM knobs. Whe

19、n “OFF”, only the active trace, chosen using the SELECT ABCD button, is controlled by POSITION and ZOOM. 6HOHFWHG?(NOT SHOWN) When a trace with a zoom of a sequence-mode waveform is selected, the “Selected” menu not shown here becomes accessible. Pressing the corresponding menu button toggles the se

20、lection between display of a single, specific “Segment” and “All Segments”. With the former selected, the associated knob can be used to step through the segments and choose one. IRU?0DWK?XVH?PD?SRLQWV For selecting the maximum number of points for all math operations a low number increases computat

21、ion speed. ? =RRP?DQG?0DWK?6HWXS?0HQXV =RRP XVH?0DWK For toggling between “No” (Zoom only) and “Yes” (Math functions) SETUP. 7UDFH?$?%?&?RU?LV?=220?RI To select the source trace to be zoomed (four-channel menu shown). ? =RRP?0DWKHPDWLFV?DQG?0DWK?6HWXS $ULWKPHWLF? allows addition, subtraction, multip

22、lication and division, as well as choice of the two operands and the operator. The example on this page shows a setup of trace A as the sum of Channels 1 and 2. XVH?0DWK To choose a math function. 0DWK?7SH To select “Arithmetic”. 6XP LIIHUHQFH 3URGXFW 5DWLR For selecting the operator. ?%?&? 0?0?0?0?

23、 To select one of two operand source traces (four-channel menu shown). SOXV?%?&? 0?0?0?0? To select the other operand source trace (four-channel menu shown). ? =RRP?DQG?0DWK?6HWXS?0HQXV $YHUDJH?offers Summed (Linear) or Continuous (Exponential) Averaging. Shown here is an example setup of trace A as

24、 a Summed Average (over 1000 sweeps) of Channel 1. See also page 102. XVH?0DWK To choose a math function. 0DWK?7SH To select, in this case, “Average” (other choices in the example menu shown here include options not available on the standard scope). $YJ?7SH To select “Summed” or “Continuous Average”

25、. IRU?ZHLJKW When “Summed” is selected, this menu (“for”) is used to define the number of sweeps. When “Continuous Average” is chosen, the same menu becomes “weight” and is used to define the weight, similar to number of sweeps. In “for” the first n sweeps will be taken into account, whereas in “wei

26、ght” the last sweep will be given a weight of 1 and the previous result a weight of n in calculating the new average. RI For selecting the source trace for averaging (four-channel menu shown). ? =RRP?0DWKHPDWLFV?DQG?0DWK?6HWXS (QKDQFHG?5HVROXWLRQ? allows the selection of low-pass digital filters tha

27、t increase the resolution of the displayed signal at the expense of its bandwidth. Appendix B gives a detailed explanation. These digital filters work very much like analog bandwidth-limit ones. In Single-Shot mode, they and the sampling speed affect bandwidth. If high bandwidth is needed at slow ti

28、mebases, averaging and repetitive sampling should be considered. XVH?0DWK To choose a math function. 0DWK?7SH To select “Enhanced Resolution”. HQKDQFH?E For selecting the filter that will enhance resolution of the displayed signal from one to three bits in 0.5-bit steps. ?%?&? 0?0?0?0? To select the

29、 source trace for filtering (four-channel menu shown). * Only with WP01 Advanced Math package. See “Signal Analysis” in Appendix A for specifications. ? =RRP?DQG?0DWK?6HWXS?0HQXV 6(783?(WUHPD? used for acquiring a trace envelope over many acquisitions (see also page 103). XVH?0DWK To choose a math f

30、unction. 0DWK?7SH To select “Extrema”. OLPLWV To select either “Envelope”, “Floor” or “Roof”. Floor shows only the lower, and Roof only the upper part of the envelope. Changing the limits does not force the analysis to start again. IRU For selecting the number of sweeps. RI To select the source trac

31、e (four-channel menu shown). Only with WP01 Math package. See “Signal Analysis” in Appendix A for specifications. ? =RRP?0DWKHPDWLFV?DQG?0DWK?6HWXS 6(783?)7? used to display the Fast Fourier Transform (FFT) of a signal and visualize it in the frequency domain. See the final section of this chapter,

32、and Appendix C, for when and how to use FFT. XVH?0DWK To choose a math function. 0DWK?7SH For selecting “FFT”. )7?UHVXOW To select the FFTs output format: “Imaginary”, “Magnitude”, “Phase”, “Power Dens”-ity, “Power Spect”-rum, “Real” or “Real + Imag”. ZLWK?ZLQGRZ Using the corresponding menu button

33、to select the FFT window type from “Rectangular”, “Hanning”, “Hamming”, “Blackman-Harris”, and “Flat-top”. And the associated knob to select “AC” or “DC”. RI For selecting the source trace (four-channel menu shown). Only with WP02 Spectral Analysis package. See “Signal Analysis” in Appendix A for sp

34、ecifications. 1RWH? During Fast Fourier Transform computation the FFT sign is displayed in the lower right-hand corner of the screen. The computation of FFT on long time-domain records can take time. The computation can be interrupted or aborted at any time using any front-panel control. ? =RRP?DQG?

35、0DWK?6HWXS?0HQXV 6(783?)7?$YHUDJH? used for displaying the FFT power averaging of an FFT source trace, power averaging being useful for characterizing broadband noise or periodic signals without a stable trigger signal. Total power signal and noise is measured at each frequency. The source trace mus

36、t be an FFT function. See the final section of this chapter, and Appendix C, for when and how to use FFT. XVH?0DWK To choose a math function. 0DWK?7SH To select “FFT AVG”. )7?UHVXOW To select the output format of the FFT Average: “Magnitude”, “Power Density”, “Power Spectrum”. IRU For selecting the

37、number of sweeps. RI To select the FFT source. Only with WP02 Spectral Analysis package. See “Signal Analysis” in Appendix A for specifications. 1RWH? FFT Average can be reset by pressing CLEAR SWEEPS. The number of currently accumulated waveforms is then shown in the Displayed Trace field of the fu

38、nction or its expansion. ? =RRP?0DWKHPDWLFV?DQG?0DWK?6HWXS 6(783?)XQFWLRQV? gives access to a menu offering a variety of Math display functions. XVH?0DWK To choose a math function. 0DWK?7SH For selecting “Functions”. )XQFWLRQ To select a function type from this list: ? “Absolute value” ? “Derivative

39、” ? “Exp (base e)” ? “Exp 10 (base 10)” ? “Identity” ? “Integral” ? “Log (base e)” ? “Log 10 (base 10)” ? “Negation” ? “Reciprocal” ? “Sinx/x” ? “Square” ? “Square root” RI For selecting the signal offset (used to compensate for any DC offset in the signal). SOXV For selecting the source trace (four

40、-channel menu shown). * Functions shown include functions available only with WP01 Math package. See “Signal Analysis” in Appendix A for specifications. 1RWHV?IRU?0DWK?)XQFWLRQV ? Square root is computed on the absolute value of the source waveform. ? For logarithmic and exponential functions the nu

41、merical value (without units) of the input waveform is used. ? For the integral function the source waveform may be offset by an Additive Constant in the range -10 16 to +1016 times the vertical unit of the source waveform. ? =RRP?DQG?0DWK?6HWXS?0HQXV 6(783?+LVWRJUDP? used to select the histogrammin

42、g function and set-up for parameter analysis. XVH?0DWK To choose a math function. 0DWK?7SH For selecting “Histogram”. 025(?+,67?6(783 To access the secondary menu offering more histogram settings. ),1?&(17(5?$1?:,7+ To calculate optimal center- and bin-width values for the histogram. +LVWRJUDP To se

43、lect up to five source parameters for histogramming. XVLQJ?XS?WR For limiting the total histogram population. Only with WP03 Parameter Analysis or DDM/PRML Disk Drive Measurements/Supplementary Disk Drive Measurements packages. See these options respective Operators Manuals. ? =RRP?0DWKHPDWLFV?DQG?0

44、DWK?6HWXS 6(783?5HVFDOH for selecting a waveform and adjusting a, the multiplication factor, and b, the additive constant, in: (a waveform) + b, where both constants can have values ranging between 1015 and +1015. XVH?0DWK To choose a math function. 0DWK?7SH For selecting “Rescale”. ?D?E To select “

45、a” or “b”. D? ?or?E? The corresponding menu button for this menu highlights the mantissa, the exponent, or the number of digits, while the associated knob changes the highlighted value. ?%?&? 0?0?0?0? To select the source trace (four-channel menu shown). ? )7?6HWXS 6HWWLQJ?8S?)7?6SDQ?DQG?5HVROXWLRQ

46、The FFT (Fast Fourier Transform) converts a time domain waveform into frequency domain spectra similar to those of an RF spectrum analyzer display. But unlike the analyzer, which has controls for span and resolution bandwidth, FFT span is determined by sampling rate, while resolution bandwidth is in

47、versely proportional to record length. )UHTXHQF?5HVROXWLRQ?ICorrectly setting up an FFT starts with the frequency resolution, or f. This parameter is the spacing of samples in the frequency domain display. The f is set by inputting the time duration of the time domain signal to the FFT. If an acquis

48、ition channel (Channel 1 or 2, or 3 or 4) is the source, then the waveform duration is the capture time: the TIME/DIV setting multiplied by ten. The relationship between capture time and frequency resolution is illustrated here. TIME CAPTURE TIME = 10 X TIME / DIV FREQUENCY AMPLITUDEAMPLITUDE f FREQUENCY RESOLUTION ACQUIRED WAVEFORM FAST FOURIER TRANSFORM (FFT) f = 1/ CAPTURE TIME ? =RRP?0DWKHPDWLFV?DQG?0DWK?6HWXS Similarly, if the source waveform is a zoom trace, the frequency resolution is the reciprocal of the displayed waveforms duration. 6HWWLQJ?WKH?6SDQThe frequency span