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Measurement Descriptions

TDSDDM1 Disk Drive Measurement Application User Manual

3–31

Where: 

s

2
s

 is the variance of the noise-free periodic signal

s

2
n

 is the variance of the noise

From the Disk Drive Measurement Application display, follow these steps:

1. Select the SNR measurement by pressing Measure (main) 

➞

 SNR (side). (If

necessary, press –more– (side) until the SNR measurement is shown.)

2. Press Pattern Duration (side). Specify a value.

The pattern duration is the length of time of the bit data pattern period in the
readback signal. The pattern duration can be an estimate, as long as the
estimate is within the tolerance that you specify in step 3; the application
will determine the exact duration of the pattern. (Due to variations in
revolution speed between disk drives, specifying the pattern duration is
necessarily an estimate.)

Figure 3–20: Specifying the SNR parameters

3. Press Duration Tolerance (side). Specify the tolerance of your pattern

duration estimate (up to 30%). Using a tighter tolerance reduces measure-
ment time.

Procedure

Summary of Contents for TDSDDM1

Page 1: ...User Manual TDSDDM1 Disk Drive Measurement Application 071 0174 02 This document supports software version 1 0 26 and above ...

Page 2: ...hnical Data and Computer Software clause at DFARS 252 227 7013 or subparagraphs c 1 and 2 of the Commercial Computer Software Restricted Rights clause at FAR 52 227 19 as applicable Tektronix products are covered by U S and foreign patents issued and pending Information in this publication supercedes that in all previously published material Specifications and price change privileges reserved Prin...

Page 3: ...under this warranty Customer must notify Tektronix of the defect before the expiration of the warranty period If Tektronix is unable to provide a replacement that is free from defects in materials and workmanship within a reasonable time thereafter Customer may terminate the license for this software product and return this software product and any associated materials for credit or refund THIS WA...

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Page 5: ...lloscope Trigger 1 7 Setting Up the Application Trigger 1 8 Hysteresis 1 9 Configuring the Input Channels 1 11 Operating Basics Functional Overview 2 1 Starting the Application 2 1 Leaving the Application 2 3 Starting the Measurement 2 4 Viewing the Waveform 2 6 Using the Local Help 2 6 Tutorial 2 7 Preparation 2 7 Example 1 Measuring the Track Average Amplitude 2 7 Example 2 Measuring the Pulse W...

Page 6: ...11 Warning Messages 3 12 Track Average Amplitude TAA 3 13 Track Average Amplitude Plus TAA Track Average Amplitude Minus TAA 3 16 Pulse Width at 50 PW50 3 18 50 Pulse Width Positive PW50 50 Pulse Width Negative PW50 3 21 Nonlinear Transition Shift NLTS 3 23 Signal to Noise Ratio SNR 3 30 Overwrite 3 34 Resolution 3 36 Asperity 3 39 Snapshot Measurements 3 41 Snapshot Measurement Definitions 3 41 T...

Page 7: ... 6 Track average amplitude TAA measurement 2 8 Figure 2 7 Pulse width at 50 PW50 measurement with cursor gating 2 9 Figure 2 8 Track profile measurement 2 11 Figure 3 1 Selecting menus 3 1 Figure 3 2 Save Setup and Recall Setup selections in the Utility menu 3 6 Figure 3 3 Selecting the sectors to measure 3 7 Figure 3 4 Localizing a measurement using cursor gating 3 8 Figure 3 5 Limit Test results...

Page 8: ...R measurement 3 30 Figure 3 20 Specifying the SNR parameters 3 31 Figure 3 21 Overwrite measurement 3 34 Figure 3 22 Resolution measurement 3 36 Figure 3 23 Asperity measurement 3 39 Figure 3 24 Snapshot measurement data 3 41 Figure 3 25 Time PT and Time TP measurements 3 43 Figure 3 26 Track profile waveform 3 45 Figure 3 27 Specifying the track profile parameters 3 47 Figure 3 28 Track profile r...

Page 9: ...isk Drive Measurement Application User Manual v List of Tables Table 1 1 Primary setup channel assignments 1 5 Table 1 2 Default input channel assignments 1 11 Table A 1 TDSDDM1 Disk Drive Measurement Application measurements A 1 ...

Page 10: ...Table of Contents vi TDSDDM1 Disk Drive Measurement Application User Manual ...

Page 11: ...ser Manual Tektronix part number 071 0130 XX provides operating instruc tions for general oscilloscope features H The International Disk Drive Equipment and Materials Association IDEMA 1995 Standards Binder section T for Test Methods is the source document for test criteria used by the TDSDDM1 Disk Drive Measurement Application Conventions This manual uses the following conventions H For brevity t...

Page 12: ... time Or contact us by e mail tm_app_supp tek com For product support outside of North America contact your local Tektronix distributor or sales office Service Support Contact your local Tektronix distributor or sales office Or visit our web site for a listing of worldwide service locations http www tek com For other information In North America 1 800 TEK WIDE 1 800 835 9433 An operator will direc...

Page 13: ...Getting Started ...

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Page 15: ...tion Compatibility The Disk Drive Measurement Application is compatible with the following Tektronix oscilloscopes H All TDS 500D and 700D Digital Phosphor Oscilloscopes with Option HD hard disk drive or Option 2M hard disk drive plus 8 MB record length H TDS 600C Digitizing Oscilloscopes with an Option HD hard disk drive H TDS 700C Color Digitizing Oscilloscopes serial number B020100 and up with ...

Page 16: ...B commands Updates You can find information about this and other applications at the Tektronix Inc web site http www tektronix com Measurement scopes index html in the Software and Drivers category Check this site for application updates that you can download and for free applications For instructions see Updates Through a Web Browser on page 1 4 Accessories There are no standard accessories for t...

Page 17: ... before you continue If you are updating the application the Readme txt file on the Tektronix ftp site supercedes the Readme txt file on the floppy disk 2 Power off the oscilloscope 3 Insert the floppy disk in the floppy disk drive and power on the oscilloscope NOTE To verify that the TDS Run Time Environment V1 1 or above is installed watch for the name to appear at the top of the display when yo...

Page 18: ...ore you continue To copy the application from a web browser follow these steps 1 Access the ftp site at ftp ftp tek com mbd support 00 index html 1 2 Scroll through the files to the TDSJIT1 application select the file and download it to your hard disk drive If necessary unzip the file 3 Copy the application from the hard disk to a blank DOS formatted floppy disk 4 Follow the Installing the Applica...

Page 19: ...el to signal assignments You can change the channel assignments to match your configuration See Configuring the Input Channels on page 1 11 for more information Table 1 1 Primary setup channel assignments Channel Description Ch 1 Read signal from the preamp channel Ch 2 Read Gate signal optional Ch 3 Sector pulse marking the beginning of the sector on the track Ch 4 Index pulse marking the beginni...

Page 20: ... setup you must specifically program the test measurement control sequences Connect the disk drive to the oscilloscope as shown in Figure 1 3 Test oscilloscope Disk drive CH 1 CH 2 Read signal differential probe Read Gate signal standard probe Figure 1 3 Secondary setup connections Secondary Setup ...

Page 21: ...edure 1 Connect the Index Sector and Read signals to channels 4 3 and 1 respectively 2 Set the oscilloscope to the desired sample rate using the horizontal SCALE knob The sample rate is usually 500 MS s or 1 2 or 4 GS s 3 Set the time interval a Fit the waveform to the screen by pressing HORIZONTAL MENU Record Length main Fit to Screen side Select ON b In the same menu select a record length appro...

Page 22: ... TDSDDM1 APP d Press Activate Application side 2 Press Trigger main Mode side See Figure 1 4 Select one of the following Sector Select Sector if you want to perform a measurement over a range of sectors rather than over the entire track The oscil loscope uses the main trigger to trigger on the Index pulse The delayed trigger is used to monitor sectors as follows Delayed trigger triggerable after E...

Page 23: ...ncluded in the measurement Figure 1 4 Selecting the sectors to measure Hysteresis Many of the measurements require a search for a local event called a peak and trough pair Set the hysteresis level so that noise will not cause false identifica tion of peaks in the Read channel waveform For a peak or trough to be found the signal must be greater than the hysteresis level Hysteresis is a global setti...

Page 24: ... follows 1 Press menu main to display the second page of menu selections 2 Press Hysteresis main Hysteresis side See Figure 1 6 3 Specify the hysteresis value The units for hysteresis are in divisions The value you enter is used for the positive hysteresis level and its negative is used for the negative level For example if you enter a value of 2 divisions the hysteresis levels are at 2 divisions ...

Page 25: ... Application Table 1 2 lists the default input channel assignments Table 1 2 Default input channel assignments Channel Description Ch 1 Read signal from the preamp channel Ch 2 Read Gate signal optional 1 Ch 3 Sector pulse marking the beginning of the sector on the track2 Ch 4 Index pulse marking the beginning of the track2 1 This signal is used for triggering only when the Trigger Mode Read Gate ...

Page 26: ...channels to match your configuration using the Input Channels menu as follows 1 From the application display go to the Input Channels menu by pressing menu main Input Channels side See Figure 1 7 2 Using the side menu buttons assign the disk drive signals to the appropriate channels Figure 1 7 The Input Channels menu ...

Page 27: ...Operating Basics ...

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Page 29: ...ence section Starting the Application After the Disk Drive Measurement Application has been installed in the oscilloscope start the application as follows 1 Press SETUP Select Application main See Figure 2 1 2 Using the general purpose knob select hd0 and then press SELECT Depending on previous actions you might not need to do this step 3 Using the general purpose knob select TDSDDM1 APP 4 Press A...

Page 30: ...Functional Overview 2 2 TDSDDM1 Disk Drive Measurement Application User Manual Figure 2 1 Starting the application ...

Page 31: ...Measurement Application and other oscilloscope functions To access primary oscilloscope functions press the desired front panel control To return to the application push the SHIFT and APPLICATION front panel menu buttons as shown in Figure 2 3 To exit the application press Utility main Exit side Push the SHIFT and APPLICATION buttons to return to the application Figure 2 3 Returning to the applica...

Page 32: ...ollows a Display the Measure menu by pressing Measure main See Figure 2 4 If the measurement you want is not shown press more side b Select a measurement c Make any further selections required by the measurement See Measurement Descriptions on page 3 11 for information about individual measurements Press menu for next menu page Figure 2 4 Selecting a measurement from the Measure menu ...

Page 33: ...e of Sectors on page 3 6 and Cursor Gating on page 3 7 3 Press Control main 4 Press Mode side to select Single or Free Run acquisition mode The Single option performs the measurement and then stops The Free Run option performs the measurement continually In the event that the measurement requires an external operation to occur before it may continue the readout changes to Pause After fulfilling th...

Page 34: ...the application Doing so may interrupt the process Viewing the Waveform To view parts of the waveform that are obscured by the measurement display readout push the CLEAR MENU button located near the lower right of the display To return to the application display push the SHIFT and APPLICATION front panel menu buttons Using the Local Help The application includes help information available from wit...

Page 35: ...1 Press SETUP Select Application See Figure 2 1 2 Using the general purpose knob select hd0 and then press SELECT 3 Using the general purpose knob select TDSDDM1 APP 4 Press Activate Application side The application starts up and displays its initial screen Example 1 Measuring the Track Average Amplitude In this example you will measure the track average amplitude TAA over a range of sectors and d...

Page 36: ...mple you will measure the pulse width at 50 PW50 and use limit testing to include a pass fail measurement result Instead of measuring around the entire track you will use cursor gating to localize the measurement In addition you will use the hysteresis feature to avoid identifying noise as actual signals 1 Select the PW50 measurement by pressing Measure main PW50 side 2 Select cursor gating by pre...

Page 37: ...e of 2 0 divs the hysteresis level ranges from 2 0 divs to 2 0 divs 5 Enable limit testing by pressing Limit Test main On Off side Select ON 6 Press Upper Limit side and use the general purpose knob to select an upper limit for this test such as 100 ms 7 Press Lower Limit side and use the general purpose knob to select a lower limit for this test such as 1 ns 8 Press menu main Control main Start s...

Page 38: ... of sectors in Example 1 do so now See step 2 on page 2 7 for information 5 Select the TAA measurement by pressing Measure main TAA side 6 Press Control main Start side to start the measurement The measure ment data is displayed The data is also stored in the reference memory Ref1 7 Start the measurement by pressing Control main Start side Wait for the results to display 8 Display the track profil...

Page 39: ...ope setup refer to the user manual for your oscilloscope The procedure varies between models The setup is always saved in the APPS TDSJIT1 TEMP directory on the oscilloscope To save the application setup follow these steps 1 Press the SHIFT and then the APPLICATION button to return to the application 2 Press Utility main Save Setup side 3 Press Save to Selected File side 4 To exit the application ...

Page 40: ...he saved oscilloscope setup from the hard disk You will also need to restart the application To recall the oscilloscope setup refer to the user manual for your oscilloscope The procedure varies between models To recall the application setup follow these steps 1 Start the application as described on page 2 7 2 Press Utility main Recall Setup side ...

Page 41: ...Reference ...

Page 42: ......

Page 43: ...structure map which shows the relationship between menus Menu Summary There are two pages of menu selections in the Disk Drive Measurement Application Press menu main to access the second page of menus Press menu for next menu page Figure 3 1 Selecting menus The following topics briefly summarize the menus Use the Measure menu to select a disk drive measurement Measurement descriptions start on pa...

Page 44: ...Starting the Measurement on page 2 4 for more information Use the Utility menu to save and recall instrument setups See Saving and Recalling Setups on page 3 5 for more information Use the Hysteresis menu to reduce the effects of noise on measurements Set thresholds such that only real peaks and troughs are measured rather than measuring noise See Hysteresis on page 1 9 for more information Use th...

Page 45: ...Index SNR Pattern Duration Duration Tolerance Bits per Pattern Overwrite Resolution Asperity Trigger Mode Start Sector Stop Sector Preamble Duration Sector Read Gate User Index Track Profile On Off Track Profile To Value At Cursor Sector At Cursor Reset Profile Control Mode Start Pause Continue Stop Utility Help Exit Save Setup Recall Setup Default Setup Menu 2 Hysteresis Hysteresis Limit Test On ...

Page 46: ...Menu Structure 3 4 TDSDDM1 Disk Drive Measurement Application User Manual ...

Page 47: ...plication settings press Utility main Save Setup side The settings are stored in the file tdsddm1 ini on the hard disk Once you have saved a setup that setup will be recalled upon starting the Disk Drive Measurement Application The tdsddm1 ini file is not updated automatically you must use Save Setup to update the file NOTE If you want to save your current configuration be sure to use the Save Set...

Page 48: ... range of sectors Before starting the measurement specify the range of sectors to be measured as follows 1 Press Trigger main Mode side Select Sector See Figure 3 3 2 Specify the sector range a Press Start Sector side b Use the general purpose knob to specify the sector c Repeat for the Stop Sector 3 If you have not already done so set the Preamble Duration as described in step 4 of Setting Up the...

Page 49: ... Figure 3 3 Selecting the sectors to measure Cursor Gating To localize a measurement to a specific area of interest you can use cursor gating With cursor gating you use the oscilloscope cursors to indicate the area of interest on the waveform record See Figure 3 4 Localizing measurement can speed up processing and eliminate unwanted data from your analysis ...

Page 50: ...ing is On the cursors are turned on and the read channel is selected 2 Place the cursors at the beginning and end of the waveform segment of interest When you perform the measurement only the data between the cursors will be measured When cursor gating is Off the application measures the full record length NOTE The cursor gating function in this menu applies to the measurements in the Disk Drive M...

Page 51: ... of the measurement in this way you can effectively size the area of interest Adding Pass Fail Results to Measurement Data You can add a pass fail test result to the measurement data based on whether the data falls within specified limits See Figure 3 5 for an example Figure 3 5 Limit Test results Use the Limit Test menu to set upper and lower limits to be used by the measurements See Figure 3 6 T...

Page 52: ...Setup Parameters 3 10 TDSDDM1 Disk Drive Measurement Application User Manual Figure 3 6 Setting pass fail limits ...

Page 53: ...ted in accordance with procedures specified in the International Disk Drive Equipment and Materials Association IDEMA Disk Drive Standard Measurement Features There are two main groups of measurement types standard measurements and snapshot measurements In addition you can use track profiles to provide a history of the track measurements See Figure 3 7 Standard measurements provide data associated...

Page 54: ...the measurement To take another measure ment press Start side again Warning Messages Standard measurements not snapshots provide a warning if the input conditions do not support accurate measurements The application warns you if the number of samples in the measurement is less than 25 Similarly the application warns you of low vertical resolution if the number of digitizing levels is below 50 ...

Page 55: ...f the data on the Read channel signal over the specified range of sectors IDEMA specifies the duration to be over one complete track revolution Figure 3 8 Track average amplitude measurement The track average amplitude measurement TAA is defined as follows TAA 1 N N 1 S i 0 Vpp i Where N is the number of positive and negative pulse pairs Vpp is the peak to peak voltage Definition ...

Page 56: ...cation performs the measurement according to the following algorithm 1 Find all of the peak to trough pairs in the data area to be measured Find the peak by searching from the first crossing of the signal above the positive hysteresis level to the crossing of the signal below the negative hysteresis level See Figure 3 9 Keep the maximum value over this range Take one sample on either side of the m...

Page 57: ...Measurement Descriptions TDSDDM1 Disk Drive Measurement Application User Manual 3 15 Peak Trough TAA Figure 3 9 TAA measurement ...

Page 58: ...er the specified range of sectors IDEMA specifies the duration to be over one complete track revolution The track average amplitude minus TAA is the average negative peak value of the data on the read channel signal over the specified range of sectors IDEMA specifies the duration to be over one complete track revolution Figure 3 10 TAA measurement The track average amplitude positive or negative m...

Page 59: ...rement do so now The application defaults to the settings specified in the Trigger menu For further information see Setting Up the Application Trigger on page 1 8 Measuring Over a Range of Sectors on page 3 6 and Cursor Gating on page 3 7 3 Press Control main Start side to start the measurement 4 Wait for the measurement to complete then view the results The application performs the measurement ac...

Page 60: ...ring the peak or trough is zero volts From the Disk Drive Measurement Application display follow these steps 1 Select the PW50 measurement by pressing Measure main PW50 side If necessary press more side until the PW50 measurement is shown 2 If you want to change trigger settings or localize the measurement do so now The application defaults to the settings specified in the Trigger menu For further...

Page 61: ...vide the result by the number of pulse pairs 7 Perform the measurement by acquiring one segment at a time measuring it and combining all the results for the final value To speed up the measure ment process the user can specify a smaller region of each track segment to measure by using the cursors or by decreasing the record length This measurement requires the user to specify the number of segment...

Page 62: ...Measurement Descriptions 3 20 TDSDDM1 Disk Drive Measurement Application User Manual Peak Trough 1 2 peak to baseline Baseline PW50 PW50 0 V Figure 3 13 Parameters for PW50 disk drive measurements ...

Page 63: ...ured Figure 3 14 PW50 measurement PW50 is defined as the pulse width at 50 of the peak value of the pulse Only peaks are measured The baseline reference for measuring the peak is zero volts PW50 is defined as the pulse width at 50 of the trough value of the pulse Only troughs are measured The baseline reference for measuring the trough is zero volts The application performs the measurement accordi...

Page 64: ...asurement Descriptions 3 22 TDSDDM1 Disk Drive Measurement Application User Manual Peak Trough 1 2 peak to baseline Baseline PW50 PW50 0 V Figure 3 15 Parameters for PW50 and PW50 disk drive measurements ...

Page 65: ...he second transition in a series of consecutive transitions is called the adjacent transition or first adjacent transition The first adjacent transition is characterized as follows when write data requires transitions on consecutive data bits the latter transition is shifted earlier in time In other words when one transition in a series occurs then the following transition occurs earlier than it s...

Page 66: ...September 1995 NLTS Initial Magnetization The NLTS initial magnetization measurement assumes the following sequence 1 The medium is initially magnetized in one direction DC erased 2 Transitions that are written by a head field in the opposite direction are shifted later by an amount e0 The NLTS initial magnetization measurement assumes the following V t Vǒt 1 2 e0 Ǔ 1 2 e0 T Vǒt 1 2 e0 ǒM0 1 2 ǓTǓ...

Page 67: ...V t is the playback voltage in the absence of nonlinear effects T is the bit period e1 is the amount of shift M1 is an integer whose unique value is determined by the polynomial used to generate the recorded pseudo noise bit sequence The measurement reports the nonlinear effect as a percentage of T that is e1 T NLTS Second Adjacent Transition The NLTS second adjacent transition is similar to the N...

Page 68: ...percentage of T that is e2 T For this measurement you must specify the polynomial used to generate a pseudo random data pattern which is written to the disk You are also responsible for specifying the cycle repeat time of the data pattern within a known tolerance From the Disk Drive Measurement Application display follow these steps 1 Access the NLTS measurements by pressing Measure main If necess...

Page 69: ...e exact duration of the data pattern you can reduce the measurement time to a minimum by specifying a Duration Tolerance of 0 The application will use the Pattern Duration that you specify without attempting to adjust to the actual duration of the data pattern 5 Press Polynomial Index side Use the general purpose knob to specify the pseudo random binary sequence polynomial This should be the same ...

Page 70: ...er settings or localize the measurement do so now The application defaults to the settings specified in the Trigger menu For further information see Setting Up the Application Trigger on page 1 8 Measuring Over a Range of Sectors on page 3 6 and Cursor Gating on page 3 7 7 Press Control main Start side to start the measurement 8 Wait for the measurement results to display ...

Page 71: ...ar Distortion Measurement Techniques Septem ber 1995 The application performs the measurement according to the following algorithm 1 Acquire three or more cycles of the waveform 2 The user specifies the polynomial used to generate the waveform the approximate duration of one period of the periodic signal captured in the waveform and the tolerance of the approximation NOTE The specified polynomial ...

Page 72: ...d by the averaging operation performed by the SNR measurement Figure 3 19 SNR measurement Signal to noise ratio is defined in terms of variances of the signal and noise and thus is independent of DC offsets of the readback voltage The SNR measure ment algorithm assumes that the acquired signal consists of a periodic signal and independent additive noise The noise is assumed to be responsible for a...

Page 73: ...Specify a value The pattern duration is the length of time of the bit data pattern period in the readback signal The pattern duration can be an estimate as long as the estimate is within the tolerance that you specify in step 3 the application will determine the exact duration of the pattern Due to variations in revolution speed between disk drives specifying the pattern duration is necessarily an...

Page 74: ...th shift registers pseudo random binary sequence the number of bits per pattern is 2L 1 where L is the order of the characteristic polynomial For example for a 9th order polynomial the value would be 511 29 1 for a 7th order polynomial the value would be 127 27 1 5 If you want to change trigger settings or localize the measurement do so now The application defaults to the settings specified in the...

Page 75: ...within a known tolerance 3 This step is not performed if the user specifies a Duration Tolerance of 0 Compute the actual cycle time and delay values SNR guarantees that the real cycle time is determined by the measurement if the initial user estimate for the cycle time is within the specified tolerance up to 30 of its real value The SNR measurement uses several cycles of the waveform to improve th...

Page 76: ...ious write after new data is written to the same location The strength of the residual signal depends on the coercivity of the media write current amplitude and saturation characteristics of the head Figure 3 21 Overwrite measurement The Overwrite measurement is defined as follows Overwrite dB 20 log ǒVr Vo Ǔ Where Vr is the residual RMS amplitude Vo is the RMS amplitude Definition ...

Page 77: ...ting Up the Application Trigger on page 1 8 Measuring Over a Range of Sectors on page 3 6 and Cursor Gating on page 3 7 5 Press Control main Start side to start the measurement The application computes the magnitude of the signal and then pauses waiting for input 6 Without erasing the previous data overwrite the track with the high frequen cy pattern 7 Press Continue side The application measures ...

Page 78: ... frequency pattern The result is expressed as a percentage From the resolution measurement you can infer the raw write density of the disk Figure 3 22 Resolution measurement The resolution measurement is the ratio of TAA at two different write frequen cies as follows Resolution TAA f2 TAA f1 100 Where f1 is the high frequency TAA measurement f2 is the low frequency TAA measurement Definition ...

Page 79: ...f you want to change trigger settings or localize the measurement do so now The application defaults to the settings specified in the Trigger menu For further information see Setting Up the Application Trigger on page 1 8 Measuring Over a Range of Sectors on page 3 6 and Cursor Gating on page 3 7 5 Press Control main Start side to start the measurement The oscilloscope performs a TAA measurement o...

Page 80: ...ase the test track 2 Write data for one revolution at a high frequency f1 3 Measure the TAA over the selected range of sectors 4 Erase the test track 5 Overwrite the track with data at a low frequency f2 6 Measure the TAA over the selected range of sectors 7 Calculate the ratio of the low frequency TAA to the high frequency TAA 8 Display the results Test Methodology ...

Page 81: ... display follow these steps 1 Select the Asperity measurement by pressing Measure main Asperity side If necessary press more side until the Asperity measurement is shown 2 Specify the Threshold by pressing Threshold side and then selecting a value The Threshold value specifies how large the positive peak signal must be before it is considered an asperity The Threshold is expressed as a voltage The...

Page 82: ...ccording to the following algorithm 1 The user enters a threshold value to specify what is considered an asperity 2 Begin testing for asperities checking each peak trough pair against the specified threshold If the TAA for a peak trough pair exceeds the threshold report an asperity 3 Display the results the sector number where the asperity occurred and the time relative to the start of the acquire...

Page 83: ...measurements are used in snapshots The vertical asymmetry measurement uses TAA values to compare the symmetry of the positive and negative pulses The vertical asymmetry is measured for each sector and then the values are averaged to provide a single vertical asymmetry value The vertical asymmetry value has no units and can range from 1 0 to 1 0 Interpret the values as follows 0 0 indicates that TA...

Page 84: ...available as an individual measure ment It is available only in the TAA and PW50 snapshot displays and is not available over the GPIB bus The timing asymmetry measurement is based on timing between pulse peaks calculated as follows A 1 4N ȍ i 1 N T1 T2 Where i indexes negative pulses N is the number of measured time intervals T1 is the time from the prior positive pulse to the current pulse T2 is ...

Page 85: ...positive peak to the next negative peak trough The time trough to peak Time TP is the time from a trough to the next positive peak These measurements are available only as part of the Snapshot measurements Time PT Time TP Peak Trough Figure 3 25 Time PT and Time TP measurements Time Peak to Trough Time PT and Time Trough to Peak Time TP ...

Page 86: ...Measurement Descriptions 3 44 TDSDDM1 Disk Drive Measurement Application User Manual ...

Page 87: ...s and to identify the location of flaws within a track Using this feature you can better observe characteristics of measurement variations around a track which may be due to causes such as head height variations or surface media defects The resulting track profile then represents the value of the measurement as a function of sector number over a range of sectors which can be specified in the Trigg...

Page 88: ...memories to store track profiles 3 Start the measurement as you normally would The measurement values are now stored as a track profile in the reference memory To clear the track profile reference memory press Track Profile main Reset Profile side You can view ongoing track profile results by setting the Control Mode to Free Run Press Control main Mode side Select Free Run When the track profile r...

Page 89: ... associated cursor displays or you cannot view the track profile cursor values 3 Move the cursor to the desired location on the track profile waveform The Value at Cursor is always expressed in volts regardless of other measure ment settings The cursor readout values in the side menu are available only with current track profile waveforms they are not available with waveforms that are later recall...

Page 90: ...ation of the progress of the entire measurement over the specified range of sectors Values are stored in the reference memory as one point per measurement result up to a maximum of 500 points If more than 500 points measurements are taken the oldest results are discarded Any unused points at the end of the reference memory record are set to null values The measurements are stored in reference memo...

Page 91: ...Appendices ...

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Page 93: ...ve pulse width of the Read signal Pulse Width at 50 Minus PW50 Measures the average negative pulse width of the Read signal Nonlinear Transition Shift Initial Magnetization NLTS Initial Mag Measures non linear transition shift due to initial DC erasure Nonlinear Transition Shift 1st Adjacent NLTS 1st Ad jacent Measures non linear transition shift due to adjacent transitions spaced 1 bit apart Nonl...

Page 94: ...Appendix A Specifications A 2 TDSDDM1 Disk Drive Measurement Application User Manual ...

Page 95: ...Index ...

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Page 97: ...ree Run acquisition mode 2 5 3 12 G Gated cursor measurements 3 7 GPIB 1 6 GPIB commands 2 6 H Help online 2 6 Hysteresis menu 1 9 3 2 I IDEMA Disk Drive Standard vii 3 11 Index trigger mode 1 8 1 11 Input Channels menu 1 11 3 2 Installation Application 1 3 Disk drive connection 1 4 Primary setup 1 5 Secondary setup 1 6 Run time environment 1 3 L Leaving the application 2 3 Limit Test Measurement ...

Page 98: ...nt example 2 8 PW50 and PW50 3 21 Q Quitting the application 2 3 R Range of sectors 3 6 Read Gate trigger mode 1 8 1 11 Readout Turning off 2 6 Recalling a setup Example 2 12 Recalling and saving setups 3 5 Requirements Run time environment installation 1 3 Resolution 3 36 S Saving a setup Example 2 11 Saving and recalling setups 3 5 Sector trigger mode 1 8 1 11 3 6 Serial number requirements 1 1 ...

Page 99: ... 8 3 2 Trigger mode 1 8 Trigger setup Application 1 8 Oscilloscope 1 7 Trigger menu 1 8 Tutorial 2 7 U Upper and lower limits 3 9 User trigger mode 1 8 Utility menu 3 2 V Vertical asymmetry 3 41 Viewing obscured parts of the waveform 2 6 W Warning messages 3 12 Waveform Viewing obscured portions 2 6 Web site 1 2 ...

Page 100: ...Index Index 4 TDSDDM1 Disk Drive Measurement Application User Manual ...

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