DDA Disk Drive Alalyzer User's Guide - Cursors/Measure &...

DDA-UG-E Rev E ISSUED: December 1999 ��

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The cursors are basic and important tools for measuringsignal values.

In Standard Display Mode, Amplitude, or Voltage, cursors —broken lines or bars running across the screen — are moved upand down the grid pixel by pixel.

Time cursors — arrows or cross-hair markers that move alongthe waveform (see symbols, at left) — can be placed at a desiredtime to read the amplitude of a signal at that time, and moved toevery single point acquired.

When a Time cursor is placed on a data point, a cross-barappears at the tail of the arrow, and at top and bottom of thecross-hair marker.

In Absolute Mode a single cursor is controlled. Readings foramplitude (using Amplitude cursors) or time and amplitude (usingTime cursors) can be displayed at the cursor location. Measuredvoltage amplitudes are relative to ground; measured times to thetrigger point.

In Relative Mode, a pair of Amplitude or Time cursors iscontrolled, providing readings on the difference between the twoin amplitude, or time and amplitude, respectively.

Amplitudes are shown in the Trace Label for each trace. WhenTime cursors are used, the time is shown below the grid. And inRelative Mode the frequency corresponding to the time intervalbetween the cursors is also displayed there.

When there are few data points displayed, Time cursor positionsare linearly interpolated between the data points. Time cursorsmove up and down along these straight line segments.

�� When using Persistence, Amplitude cursors are the same as inStandard Display (see above). Time cursors are vertical bars runningdown the screen and moving across it.

�� ISSUED: December 1999 DDA-UG-E Rev E

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��!"�#��$��% In XY Display, Absolute Amplitude cursors are horizontal and verticalbars that can be moved both up and down and from side-to-sideacross the screen. Relative Amplitude cursors are pairs of bars thatmove in the same way. Absolute and Relative Time cursors behaveas they do in Standard Display.

Combinations of the amplitude values are shown on the left-handside of the grid in the following top-to-bottom order:

1. “∆Y value / ∆X value” ................. Ratio

2. “20 ∗ log 10 (ratio)”..................... Ratio in dB units

3. “∆Y value ∗ ∆X value” ................ Product

4. “� = arc tan (∆Y / ∆X)

range [–180° to +180°]”..................... Angle (polar)

5. “r = sqrt (∆X ∗ ∆X + ∆Y ∗ ∆Y)” ... Radius (distance to origin).

The definition of ∆X and ∆Y depends on the cursor used. The tablebelow shows how ∆X and ∆Y are defined for each type ofmeasurement.

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TAbs

AAbs ARel Org = (0,0) Org = VXOffset

VYOffset

TRel

�X VXRef – 0 VXDif – VXRef VXRef – 0 VXRef – VXOffset VXDif – VXRef

�Y VYRef – 0 VYDif – VYRef VYRef – 0 VYRef – VYOffset VYDif – VYRef

WHERE:

AAbs Absolute Amplitude cursors VXRef Voltage of the Reference cursor on the X trace

ARel Relative Amplitude cursors VYRef Voltage of the Reference cursor on the Y trace

TAbs Absolute Time cursors VXDif Voltage of the Difference cursor on the X trace

TRel Relative Time cursors VYDif Voltage of the Difference cursor on the Y trace

Org Origin


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��&�� Press — to access the “MEASURE” Setup menus.

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To select “Cursors”.

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For selecting “Time” (time or frequency cursors) or “Amplitude”(voltage or amplitude cursors).

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To toggle between “Relative” and “Absolute”. The first displays twocursors, Reference and Difference, and indicates either the voltageor time and voltage between the two. The second shows a singlecursor that indicates either voltage compared to ground level, or thisand time compared to the trigger point.

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To select: “Diff – Ref”, which shows the subtraction betweendifference and reference cursor amplitudes; or “Diff & Ref”, whichdisplays the amplitude values for each cursor. Not available inpersistence mode.

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To control the Reference cursor available with Relative cursors,using the associated menu knob. With “Track” “ON”, both Referenceand Difference cursors are controlled by this knob and movetogether, a constant time or voltage interval maintained betweenthem. This tracking interval is represented by a bar — horizontal fortime; vertical for voltage — appearing, respectively, at the top andleft-hand edge of the grid.

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For controlling the Difference cursor, available when “Relative” isselected from “type” (see above), using the associated menu knob.

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For controlling the Absolute cursor, available when “Absolute” isselected from “type” (see above), using the associated menu knob.


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�� Press to access menus that let you customize specialfunctions. The contents of the Custom Menu will varyaccording to the options installed in the oscilloscope.

DDA-125 OOnnllyy

Press the CURSOR/MEASURES button; the following options will bedisplayed:

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Refer to “Measure – Cursors” on page 21-3 of this manual.

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Refer to “Parameters: Automatic Measurements” starting onpage 21-6 of this manual.

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Refer to “Pass/Fail Testing” on page 21-15 of this manual.

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Refer to Custom Menu on page 21-5 of this manual.


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DDA-125 OOnnllyy

Press the CUSTOM button to access these custom applications:

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This wizard steps you through jitter timing and measurementsetups. Refer to the Jitter and Timing Analysis (JTA) Manual.

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Refer to the Mask Tester Operator’s Manual.

��(��Refer to the PMA1 Software Operator’s Manual.

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Refer to the Chapter 6.


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Using signal parameters, the instrument can determine certainsignal properties automatically. The parameters that the DDAmeasures are listed and described in the Disk Drive AnalyzerReference Manual.

For common measurements on a lone signal, parameters can bemeasured in either of two standard classes or modes: in theamplitude or the time domain.

On different signals, they can be customized and used to determineup to five of the quantities on the parameter list. Customizedparameter measurements can also be used for Pass/Fail testing incomparison with chosen limits (see page 21–15). Several othermodes are available, according to the parameters and optionsinstalled in the DDA (not all modes illustrated are necessarilyavailable).

Statistics on the parameter values are accumulated, and can bedisplayed for all modes.

In addition to the overall number of sweeps used, each parameterhas its average, lowest, and highest value. The standard deviation ofthe parameter is also calculated.

��%�.�� The algorithms that determine pulse waveform parameters are ableto detect those situations where the mathematical formulas may beapplied. However, the results obtained should be interpreted withcaution. In such cases, the DDA displays the name of the parameterand its value separated by a graphic symbol, which acts either asinformation on the parameter or as a warning. The following tableexplains these symbols.


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The parameter has been determined for severalperiods (up to 100), and the average of thosevalues has been taken.

The parameter has been determined over anintegral number of periods.

The parameter has been calculated on a histogram.

Insufficient data to determine the parameter.

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Amplitude histogram is flat within statisticalfluctuations; minimum and maximum are used toassign top and base.

Only an upper limit could be estimated (the actualvalue of the parameter may be smaller than thedisplayed value.

The signal is partially in overflow.

The signal is partially in underflow.

The signal is partially in overflow and in underflow.


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This mode measures, for a single trace:

� peak-to-peak (amplitude between maximum and minimum samplevalues)

� mean of all sample values

� standard deviation

� root mean square of all sample values

� amplitude of the signal

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Use this to select Parameters.

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This is for selecting the Standard Voltage mode.

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This is for turning On display of the parameter’s average, lowest,highest, and standard deviation, as well as the number of sweepsincluded in the statistics. It is cleared each time the acquisitionconditions change or when the CLEAR SWEEPS button is pressed.As long as Parameters is highlighted in the top menu, theaccumulation of statistics continues, even if the statistics are notshown.

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Use this to select the trace for which the voltage parameters aremeasured. The choices available in this menu will depend on thetraces displayed (a maximum of four traces can be displayed).Here Traces 1 and 2 are displayed, and 2 is selected.

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By means of the associated menu knob, use this to determinethe starting point (in screen divisions) for parametermeasurements. “Track” On links control of both the start and endpoints of the parameter measurement so that they can be movedtogether, using the associated menu knob.

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Use this to determine the end point (in screen divisions). It also indicatesthe total number of data points used for the measurements.


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For a single trace, this mode measures:

� period

� width (at 50% amplitude)

� rise time (10 to 90% of amplitude)

� fall time (90 to 10% of amplitude)

� delay (from trigger to first 50% amplitude point)

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This is for selecting the Standard Time mode.

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This is for turning On display of the parameter’s average, lowest,highest, and standard deviation, as well as the number of sweepsincluded in the statistics. It is cleared each time the acquisitionconditions change or when the CLEAR SWEEPS button is pressed.

As long as Parameters is highlighted in the top menu, theaccumulation of statistics continues, even if the statistics are notshown.

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This is for selecting the trace for which the time parameters are to bemeasured. The choices available in this menu will depend on thetraces displayed (a maximum of four traces can be displayed).Here Traces 1 and 2 are displayed, and 2 is selected.

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Use this to determine the starting point (in screen divisions) forparameter measurements. “Track” On, links control of both the startand end points of the parameter measurement so that they can bemoved together, using the associated menu knob.

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Use this to determine the end point, in screen divisions. It alsoindicates the total number of data points used for the measurements.


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In this mode, up to five parameters can be displayed for varioustraces.

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This is for selecting Parameters.

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This is for selecting the Custom mode.

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This is for turning On the display of the parameter’s average, lowest,highest, and standard deviation, as well as the number of sweepsincluded in the statistics. It is cleared each time the acquisitionconditions change or when the CLEAR SWEEPS button is pressed.

As long as Parameters is highlighted in the top menu, theaccumulation of statistics continues, even if the statistics are notshown.

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This is for accessing the secondary “CHANGE PARAM” menu (seefollowing pages).

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Use this to determine the starting point (in screen divisions) forparameter measurements. “Track” On links control of both the startand end points of the parameter measurement so that they can bemoved together, using the associated menu knob.

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Use this to determine the end point in screen divisions.


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�0�12�� This is for modifying parameters.

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Use this to select up to five different parameters (1, 2, 3, 4, or 5) formodification.

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Use this to specify the category of parameter. When All is selected,the “measure” menu (see below) will show all parameters. However,when a particular category is selected, only those parameters in thecategory are shown.

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This is for deleting all parameters previously selected.

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Use this to choose the new parameter to be measured on this line.When “– –” is selected, the line is not used.

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This is for selecting the channel or trace on which the parameter willbe measured.


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�0�12�� Parameters can be customized to meet specific needs:

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Use this to specify the category or type of parameter.

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This calls up the ∆t@lv customization menu (next page).

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Use this to select ∆t@lv.

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By means of the menu button, this selects the channel — 1, 2 (3 or4) — or memory (A, B, C, or D). The knob selects from which, andto which, channel the measurement is to be made.


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�� ∆t@lv (for example) is used for customizing the ∆t@lv parameter(see the DDA Reference Manual for descriptions of all standardparameters).

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This is for selecting whether the levels should be set in absolute orpercentage of the peak-to-peak signal value.

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Use this to set the hysteresis division. A voltage band is extendedequidistantly above and below the selected level. In order for thesignal to be considered valid, and not as noise, the signal mustexceed the upper or lower limits of this band by half the hysteresisdivision setting.

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This is for selecting the voltage or amplitude percentage setting ofthe level on the waveform at which the timing is to be measured. It isalso used to select whether the measurement should be made on aPositive (rising) edge, or a Negative (falling) edge or, with First, oneither type of edge.

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This is for selecting the voltage or amplitude percentage setting ofthe level on the waveform at which the timing is to end. It is also usedto select whether it should finish on a Positive (rising) edge, or aNegative (falling) edge or, with First, on either type of edge.


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�� ∆c2d+ (for example) is used for customizing the ∆c2d+ parameter(see the DDA Reference Manual for descriptions of all standardparameters).

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Use this to set the hysteresis division. A voltage band is extendedequidistantly above and below the selected level. In order for thesignal to be considered valid, and not as noise, the signal mustexceed the upper or lower limits of this band by half the hysteresisdivision setting.

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Use this to select the clock edge or edges used for this parametermeasurement.

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This is for selecting the data edge or edges used for themeasurement.


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Parameters can also be used in carrying out Pass/Fail tests.These tests require a combination of measurements withinchosen limits, using an action provoked when the test eitherpasses or fails, depending on which has been specified.Signals can also be Pass/Fail tested in comparison with atolerance mask.

Up to five parameters can be tested at the same time. Intolerance mask testing, a trace can be compared to a tolerancemask.

Whether the tests pass or fail, any or all of the following actionscan be invoked:

� Stop capturing further signals

� Dump the screen image to a hardcopy unit

� Store selected traces in internal memory, on a memory card(optional), or on a floppy disk

� Sound the buzzer

� Emit a pulse on the CAL BNC

The Pass/Fail display will show:

� Results on the current waveforms

� Number of events passing

� Total number of sweeps treated

� Actions to be taken


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Use this to select Pass or Fail.

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This is for turning testing Off or On. Turn testing off to observe onlythe parameter variations.

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Use this to access the secondary “CHANGE TEST” menu (see nextpage).

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Use this to determine the starting point, in screen divisions, forparameter measurements.

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Use this to determine the end point in screen divisions.


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Use this to select Param or, if no test is required, --- (No Test).

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Use this to select Param.

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This is for deleting all tests previously selected.

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This is for selecting the new parameter to be measured on this line.When – – is selected, the line is not used.

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This is for selecting the channel or trace on which the parameter willbe measured.


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Use this to Select Param or --- (No Test) if no test required on theselected line (see “Mask” selection, page 21–19).

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Use this to select Limit (see “Param” 21–17).

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This is for deleting all tests previously selected.

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This is for selecting the appropriate relation — less than or greaterthan.

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Use this to choose one of three modifications of a limit: its mantissa,exponent, and the number of digits for the representation of itsmantissa. The corresponding menu button is used to select, and theassociated knob to modify the number in that field.

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Use this to set the limit to the latest measured value — a startingvalue for the final adjustment.


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Use this to select up to five different parameters (1, 2, 3, 4, or 5) formodification (“Action” selection, page 21-20).

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This is for selecting Mask or --- (No Test) if no test is required on theselected line (“Param” 21–17).

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Use this to access the secondary menu for modifying mask settings.

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This is for choosing this mask test condition.

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Use this to select channel or trace for testing.

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This is for choosing this mask test condition.

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Use this to select mask trace A, B, C, or D.

��Pass/Fail testing against a mask is affected byhorizontal and vertical zooming of the mask trace. The testwill be made inside the area bordered by the parametercursors. Timebases of the mask and the trace under testshould be identical. For visual mask testing, a single gridshould be used when performing a mask test on a singletrace; two grids should be used for testing on two traces.


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Use this to select W’form.

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This is for selecting D=M4 if the mask is to be automaticallydisplayed on the screen. Otherwise select M1, M2, M3, or M4.

Using “RECALL W’FORM” (see previous chapter) memories M1through M4 can be recalled to traces A through D for display.

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Use this to generate an inverted mask.

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This is for selecting the waveform to be used as reference. Themask will be generated around this waveform.

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Use this to generate the mask.

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This is for selecting tolerance in amplitude, using the associatedknob.

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This is for selecting tolerance in time, using the associated menuknob.


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Use this to select the device.

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This is for selecting D=M4 to automatically display the mask on-screen, or for selecting M1, M2, M3, or M4.

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This is for generating an inverted mask.

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Use this to recall the mask.

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Use this to select the appropriate mask, using the associated menuknob.


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Depending on the test result certain actions can be taken.

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This is for selecting Action.

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Use this to delete all previously selected actions.

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Use this to determine if the action will be taken on PASS or FAIL.

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This is for selecting the action. The selected action will then beactivated in the menu below.

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Use this to perform (Yes) or disable (No) the action chosen in the“Then” menu (above). The choice will be indicated alongside theselected action in “Then.”

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DDA Disk Drive Alalyzer User's Guide - Cursors/Measure &...

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