Tektronix 1502C User Manual
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Tektronix 1502C User Manual

Metallic time-domain reflectometer
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  • Page 1 T h e t e s t & me a s u r e me n t e q u i p me n t y o u n e e d a t t h e p r i c e y o u w a n t . A l l t e s t I n s t r u me n t s , I n c .
  • Page 2 User Manual 1502C Metallic Time-Domain Reflectometer 070-7169-05 This document applies for firmware version 5.04 and above. www.tektronix.com...
  • Page 3 Copyright © Tektronix, Inc. All rights reserved. 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. Tektronix, Inc., P.O. Box 500, Beaverton, OR 97077...
  • Page 4 Tektronix, with shipping charges prepaid. Tektronix shall pay for the return of the product to Customer if the shipment is to a location within the country in which the Tektronix service center is located. Customer shall be responsible for paying all shipping charges, duties, taxes, and any other charges for products returned to any other locations.
  • Page 5 6:00 a.m. – 5:00 p.m. Pacific time This phone number is toll free in North America. After office hours, please leave a voice mail message. Outside North America, contact a Tektronix sales office or distributor; see the Tektronix web site for a list of offices.

  • Page 6: Table Of Contents

    1–1 Preparing to Use the 1502C .........
  • Page 7 ....... . D–1 Pulse Echo Testing of Electrical Transmission Lines Using the Tektronix Time-Domain Reflectometry Slide Rule ... D–1 Terms and Symbols .
  • Page 8 ... . . 1–3 Figure 1–3: 1502C Front-Panel Controls ..... . .
  • Page 9 ........2–25 1502C MTDR User Manual...
  • Page 10 ..........D–9 1502C MTDR User Manual...
  • Page 11 ..... A–3 Table A–3: Physical Characteristics ......A–5 1502C MTDR User Manual...

  • Page 12: General Information

    These will be displayed as hills and valleys in the reflected pulse. The 1502C is capable of finding shorts, opens, defects in the shield, foreign substances in the cable (e.g., water), kinks, and more.

  • Page 13: Installation And Repacking

    Performance Checks appendix. These checks should satisfy the requirements for most receiving or incoming inspections. Power Source and Power The 1502C is intended to be operated from a power source that will not apply Requirements more than 250 volts RMS between the supply conductors or between either supply conductor and ground.

  • Page 14: Table I: Shipping Carton Test Strength

    31 – 120 121 – 140 141 – 160 2. Install the front cover on the 1502C and surround the instrument with polyethylene sheeting to protect the finish. 3. Cushion the instrument on all sides with packing material or urethane foam between the carton and the sides of the instrument.
  • Page 15 General Information 1502C MTDR User Manual...

  • Page 16: Safety Summary

    The safety information in this summary is for operating personnel. Specific warnings and cautions will be found throughout the manual where they apply, but might not appear in this summary. For specific service safety information, see the 1502C Service Manual. Safety Terms and Symbols Terms in this manual: WARNING.
  • Page 17 This instrument contains a lead-acid battery. Some states and/or local jurisdic- tions might require special disposition/recycling of this type of material in accordance with Hazardous Waste guidelines. Check your local and state regulations prior to disposing of an old battery. 1502C MTDR User Manual...
  • Page 18 General Safety Summary Tektronix Factory Service will accept 1502C batteries for recycling. If you choose to return the battery to us for recycling, the battery cases must be intact, the battery should be packed with the battery terminals insulated against possible short-circuits, and should be packed in shock-absorbant material.
  • Page 19 General Safety Summary 1502C MTDR User Manual...

  • Page 20: Operating Instructions

    This procedure is explained in the 1502C Service Manual. The 1502C can be stored in temperatures ranging from –62° C to +85° C if a battery is not installed. If a battery is installed and the storage temperature is below –35°...

  • Page 21: Figure 1-1: Rear Panel Voltage Selector, Fuse, Ac Receptacle

    The 1502C can be powered by a rechargeable lead-gel battery pack that is accessible only by removing the case from the instrument. When AC power is applied, the battery pack is charged at a rate that is dependent on the battery charge state.

  • Page 22: Figure 1-2: Display Showing Low Battery Indication

    If the battery is low, it will be indicated on the LCD (bat/low). If this is the case, protective circuitry will shut down the 1502C within minutes. Either switch to AC power or work very fast. If the instrument is equipped with a chart recorder, using the recorder will further reduce the battery level, or the added load might shut down the instrument.
  • Page 23 ≥ +5° C for 24 hours. When operating the 1502C in an environment below +10° C, a heater will activate. The element is built into the LCD module and will heat the display to permit normal operation.

  • Page 24: Preparing To Use The 1502C

    Operating Instructions Preparing to Use the 1502C Check the power requirements, remove the front cover, and you are ready to test cables. The following pages explain the front-panel controls. Tektronix METALLIC TDR 1502C CABLE TESTER POSITION 0.00 ft MENU VIEW...

  • Page 25: Display

    0.00 ft View Input Grid Indicator View Store Indicator View Difference Indicator Store Indicator 1 avg 500 mr 0.2 ft Selected Selected Selected Noise Filter Vertical Scale Distance per Division Figure 1–4: Display and Indicators 1–6 1502C MTDR User Manual...

  • Page 26: Front-Panel Controls

    Operating Instructions Front-Panel Controls 1. CABLE: A female BNC connector for attaching a cable to the 1502C for testing. 2. NOISE FILTER: If the displayed waveform is noisy, the apparent noise can NOISE FILTER be reduced by using noise averaging. Averaging settings are between 1 and 128.

  • Page 27: Menu Selections

    Vp values. These are nominal values. The manufacturer’s listed specifications should be used whenever possible. c. Impedance Values displays impedances of common cables. In some cases, these values have been rounded off. Manufacturer’s specifications should be checked for precise values. 1–8 1502C MTDR User Manual...
  • Page 28 Hold can be deactivated by pushing STORE or the mode exited by using the Setup Menu. ii. Pulse Is: On/Off. Turns the pulse generator off so the 1502C does not send out pulses. iii. Single Sweep Is: On/Off. This function is much like a still camera; it will acquire one waveform and hold it.
  • Page 29 LCD Chart allows adjusting the number of dots per segment and the number of prints (strikes) per segment. ii. Head Alignment Chart generates a pattern to allow mechanical alignment of the optional chart recorder. 1–10 1502C MTDR User Manual...
  • Page 30 The SP-232, a serial interface product, also allows for connection of the 1502C to other instrumentation, including computers, via the option port. SP-232 is an RS-232C-compatible interface. For more information, contact your Tektronix Customer Service Representative. They can provide you with additional details on the hardware and software protocol.

  • Page 31: Test Preparations

    It is sometimes expressed as a whole number (e.g., 66) or a percentage (e.g., 66%). On the 1502C, it is the percentage expressed as a decimal number (e.g., 66% = .66). If you do not know the velocity of propagation, you can get a general idea from the following table, or use the Help with Cables section of the Cable Information menu.

  • Page 32: Figure 1-5: Vp Set At .30, Cursor Beyond Reflected Pulse

    Figure 1–5: Vp Set at .30, Cursor Beyond Reflected Pulse (Set Too Low) 3.000 ft Figure 1–6: Vp Set at .99, Cursor Less Than Reflected Pulse (Set Too High) 3.000 ft Figure 1–7: Vp Set at .66, Cursor at Reflected Pulse (Set Correctly) 1–13 1502C MTDR User Manual...

  • Page 33: Cable Test Procedure

    Operating Instructions Cable Test Procedure Distance to the Fault Be sure to read the previous paragraphs on Vp. 1. Set the 1502C controls: POWER CABLE Cable to BNC NOISE FILTER 1 avg VERT SCALE 500 mr DIST/DIV (see below) (per cable) 2.

  • Page 34: Figure 1-9: Short In The Cable

    4. When inspecting a 452-foot cable, a setting of 50 ft/div allows a relatively fast inspection. If needed, turn VERT SCALE to increase the gain. The higher the gain, the smaller the faults that can be detected. If noise increases, increase the NOISE FILTER setting. 1–15 1502C MTDR User Manual...

  • Page 35: Figure 1-11: 455-Ft Cable

    (e.g., water in the cable). Inductive faults appear as a rising of the pulse (e.g., fray). Whenever an abnormality is found, set the cursor at the beginning of the fault and read the distance to the fault on the distance window of the LCD. 1–16 1502C MTDR User Manual...

  • Page 36: Figure 1-13: Reflection Adjusted To One Division In Height

    It will show as a downward shift or dip on the waveform. If the cable has an open or short, all the energy sent out by the 1502C will be reflected. This is a reflection coefficient of rho = 1, or +1000 mr for the open and –1000 mr for the short.

  • Page 37: Figure 1-14: Return Loss

    Return Loss (in dB) = –20 * log (base ten) of Absolute Value of Rho (V The 1502C can be made to display in dB instead of mr/div through the menu: 1. Press MENU.

  • Page 38: Figure 1-15: Ohms-At-Cursor

    Operating Instructions Ohms-at-Cursor The 1502C can compute and display what impedance mismatch would cause a reflection as high (or low) as the point at the cursor. This measurement is useful for evaluating the first impedance mismatch (first reflection) or small impedance changes along the cable (e.g., connectors, splices).

  • Page 39: Figure 1-16: Display With View Input Turned Off

    The front panel control settings and the menu-accessed settings are also stored. They are accessed under View Stored Waveform Settings in the first level of the menu. 3.000 ft Figure 1–17: Display of a Stored Waveform 1–20 1502C MTDR User Manual...

  • Page 40: Figure 1-18: Display Of A Stored Waveform

    One method to minimize the overlapping of the waveforms in VIEW DIFF is: 1. Move the waveform to be stored into the top half of the display. 1–21 1502C MTDR User Manual...

  • Page 41: Figure 1-19: Waveform Moved To Top Half Of Display

    4. Push VIEW STORE and the stored waveform will appear above the current waveform. 3.000 ft Figure 1–20: Current Waveform Centered, Stored Waveform Above 5. Push VIEW DIFF and the difference waveform will appear below the current waveform. 1–22 1502C MTDR User Manual...

  • Page 42: Figure 1-21: Current Waveform Center, Stored Waveform Above, Difference Below

    H When this is done, great care should be taken to make sure the vertical and horizontal scales are identical for the two waveforms being compared. If either the stored or current waveform is clipped at the top or bottom of the display, the difference waveform will be affected. 1–23 1502C MTDR User Manual...

  • Page 43: Figure 1-22: Waveform Of Three-Foot Lead-In Cable

    4. Turn the NOISE FILTER control to 1 avg. The instrument is now in HORZ SET REF, or delta mode. The distance window should now read 0.00 ft. As the cursor is scrolled down the cable, the distance reading will now be from the new zero reference point. 1–24 1502C MTDR User Manual...

  • Page 44: Figure 1-24: Cursor Moved To End Of Three-Foot Lead-In Cable

    POSITION control until the distance window reads 0.00 ft. 0.000 ft move cursor to reference and Press STORE Figure 1–25: Cursor Moved to 0.00 ft d. Push STORE. e. Turn NOISE FILTER to desired setting. 1–25 1502C MTDR User Manual...

  • Page 45: Figure 1-26: Incident Pulse At Three Divisions

    Vertical Compensation for When testing cables other than 50W, this procedure allows reflection measure- Higher Impedance Cable ments in millirho. 1. Attach a short sample of the given cable (75 W in this example) to the instrument. 1–26 1502C MTDR User Manual...

  • Page 46: Figure 1-27: Waveform Of Short 75 Ohm Cable

    STORE Figure 1–28: Waveform Centered and Adjusted Vertically 5. Press STORE. 6. Return NOISE FILTER to the desired setting. 7. Adjust the POSITION control to the desired position on the waveform to measure loss. 1–27 1502C MTDR User Manual...

  • Page 47: Figure 1-29: Cursor Moved To Desired Position

    Adjust VERT SCALE to obtain an incident pulse height of two divisions. c. Push STORE. d. Turn NOISE FILTER to desire filter setting. The instrument can be turned off and back on to default to the two division pulse height. 1–28 1502C MTDR User Manual...

  • Page 48: Additional Features (Menu Selected)

    Additional Features (Menu Selected) Max Hold The 1502C will capture and store waveforms on an ongoing basis. This is useful when the cable or wire is subjected to intermittent or periodic conditions. The 1502C will monitor the line and display any fluctuations on the LCD.

  • Page 49: Figure 1-31: Waveform Showing Intermittent Changes

    Hold, and push MENU repeatedly until the instrument returns to normal operation. Pulse On/Off This feature puts the 1502C in a “listening mode” by turning off the pulse generator. 1. Attach a cable to the 1502C front-panel CABLE connector. 2. Push MENU to access the Main Menu.
  • Page 50 The input circuitry is very sensitive and can be easily damaged by even moderate level signals. NOTE. In this mode, the 1502C is acting as a detector only. Any pulses detected will not originate from the instrument, so any distance readings will be invalid.
  • Page 51 Figure 1–33: A Captured Single Sweep 8. To exit Single Sweep is: On, access the Acquisition Control Menu again, turn the Single Sweep back off, then repeatedly push MENU until the instrument returns to normal operation. 1–32 1502C MTDR User Manual...

  • Page 52: Operator Tutorial

    1502C can show many previously hidden faults. You, the Operator The 1502C is a highly accurate cable tester. It is easy to use and will provide fast, accurate measurements. Because of electrical and environmental differences in cables and their applications, each waveform will likely differ. The best way to learn these differences is experience with the instrument.

  • Page 53: Getting Started

    Getting Started Let’s start by inspecting a cable. For the next few examples, we will use the 3-foot precision test cable provided with the 1502C (Tektronix part number 012–1350–00). 1. Pull on the POWER switch. The instrument will initialize, give instructions for accessing the menu, and enter normal operation mode.
  • Page 54 4. Adjust the VERT SCALE control. This will increase the height of the pulse. For accurate measurements, the pulse should occupy most of the display. Note that the LCD shows the VERT SCALE setting in mr. For now, set this control to 354 mr/div. 2–3 1502C MTDR User Manual...
  • Page 55 (e.g., jumper wire). 7. Remove the short. With a little practice, you will be able to identify many kinds of cable faults. 2–4 1502C MTDR User Manual...

  • Page 56: The Waveform Up Close

    POSITION control counterclockwise until the distance window reads –2.000 ft. The cursor will be on the far left side of the display and the reflected pulse will be near center. 2. Set the 1502C front-panel controls: CABLE 3-ft test cable, no short...
  • Page 57 The bumps following the incident pulse are the aberrations from the internal circuitry and reflections between the open end of the cable and the front panel. –0.520 ft Front-panel Connector Figure 2–7: 3-foot Cable with Cursor at Incident Pulse, Vertical Scale at 25 dB 2–6 1502C MTDR User Manual...

  • Page 58: A Longer Cable

    Obtain a known length of 50 W cable. For this example, we are using a coaxial cable approximately 452 feet long. Your cable length will probably differ, but the following test procedure remains fundamentally correct for any cable length up to 2,000 feet. 1. Set the 1502C front-panel controls: CABLE available longer cable NOISE FILTER...

  • Page 59: Ohms-At-Cursor

    1 ft/div. Ohms-at-Cursor Using the long cable as an example, we can find the impedance at the cursor. 1. Set the 1502C front-panel controls: CABLE available longer cable...
  • Page 60 There is less loss at the beginning of the cable because there is less series resistance. 17.880 ft 50.9 W Figure 2–11: Ohms-at-Cursor Near Beginning of Cable 8. Turn the POSITION control clockwise to set the cursor past the reflected pulse. Note that the ohms-at-cursor reading is ≥1 kW. 2–9 1502C MTDR User Manual...
  • Page 61 This is especially true very near the instrument where some aberrations are still significant. See the Ohms-at-Cursor section of the Operating Instructions chapter for more on the limitations of this feature. 2–10 1502C MTDR User Manual...

  • Page 62: Noise

    Noise On a longer cable, “grass” might appear on the displayed waveform. This is primarily caused by the cable acting as an antenna, picking up nearby electrical noise. 1. Set the 1502C front-panel controls: CABLE 3-ft cable NOISE FILTER 1 avg...
  • Page 63 Because there are no large discontinuities, it appears to the instrument as an endless cable. The noise seen in this demonstration is noise picked up on the cable and a tiny amount of internal noise in the 1502C. When testing cables, the noise filter is extremely effective in reducing noise.

  • Page 64: Set Ref (Delta Mode)

    If, for example, you have a 3-foot cable leading to a patch panel, you could eliminate this jumper from your distance readings. 1. Set the 1502C front-panel controls to: CABLE Attach 3-ft cable...
  • Page 65 7. To exit HORZ SET REF, do the following: a. Set the POSITION control to exactly 0.00 ft (you might have to set DIST/DIV to .1 ft/div). b. Push STORE. c. Turn the NOISE FILTER control to the desired noise setting. 2–14 1502C MTDR User Manual...
  • Page 66 The VERT SET REF function allows manual control of the vertical calibration of the 1502C. This can be used to compensate for cable loss or to increase the resolution of the millirho scale. The following example shows how to compen- sate for cable loss.
  • Page 67 VERT SET REF. NOTE. Care must be taken in changing the VERT SET REF because of the calibration change. The 1502C automatically starts the pulse at two divisions high. When you change the vertical reference, you essentially defeat this function.

  • Page 68: View Input

    Operator Tutorial VIEW INPUT This push button allows you to view what is coming in the CABLE connector, or to eliminate it from the display. 1. Set the 1502C front-panel controls to: CABLE Attach 3-ft cable NOISE FILTER 1 avg...

  • Page 69: Store And View Store

    This function can be used to make the display less busy when viewing stored waveforms. STORE and VIEW STORE These functions allow you to store a waveform and view the stored waveform. 1. Set the 1502C front-panel controls to: CABLE Attach 3-ft cable NOISE FILTER...
  • Page 70 Figure 2–26: Waveform with Both Current and Stored Waveforms Comparing new cables with old cables, or repaired cables with damaged cables is easy using these two pushbuttons. Leave the instrument in this condition for the next lesson. 2–19 1502C MTDR User Manual...

  • Page 71: View Diff

    DIFF function. Pressing this button with no waveform in storage will caused an error message to be displayed. If the stored waveform and the current waveform are identical, the difference waveform will appear as a straight line. 2–20 1502C MTDR User Manual...

  • Page 72: Menu-Accessed Functions

    Menu-Accessed Functions NOTE. If you get lost or confused while in a menu, repeatedly press the MENU button until the instrument returns to normal operation mode. Max Hold 1. Set the 1502C front-panel controls to: CABLE Attach 3-ft cable NOISE FILTER...
  • Page 73 0.000 ft Figure 2–30: Waveform Strobed Down Display in Max Hold 17. Press STORE. The display will clear, awaiting STORE to be pressed again, which would activate another Max Hold monitor cycle. 2–22 1502C MTDR User Manual...
  • Page 74 18. To exit Max Hold, access the Acquisition Control Menu again, turn off Max Hold, and push MENU repeatedly until the instrument returns to normal operation. Pulse On / Off 1. Set the 1502C front-panel controls to: CABLE Attach 3-ft cable NOISE FILTER...
  • Page 75 Figure 2–31: Display with Pulse Turned Off CAUTION. This function is used mostly for troubleshooting by qualified techni- cians. It is not recommended that you use the 1502C as a stand-alone monitor- ing device. The input circuitry is very sensitive and can be easily damaged by even moderate level signals.
  • Page 76 0.000 ft Figure 2–32: Test Cable 11. Short the far end of the test cable. 12. Press VIEW INPUT. The 1502C has done a single sweep, capturing just one frame. 0.000 ft Figure 2–33: Captured Single Sweep of Shorted Test Cable 13.

  • Page 77: Tdr Questions And Answers

    1 ns/ft in a vacuum would mean a distance of 15 feet. Because the cable is slower, we multiply the distance by the Vp (.66 in this case) and arrive at a distance of 10 feet. Of course, the 1502C does all this automatically and displays the information on the LCD.
  • Page 78 Q12: Why should cables of the same impedance be used? A12: Because a mismatch of impedance means a loss of energy at the mismatch. Q13: Why is that important to us? A13: Because a TDR displays the energy reflected back from an impedance mismatch. 2–27 1502C MTDR User Manual...
  • Page 79 Operator Tutorial 2–28 1502C MTDR User Manual...

  • Page 80: Options And Accessories

    Power Cord Options The following power cord options are available for the 1502C TDR. Note that these options require inserting a 0.15 A fuse in the rear panel fuse holder. NOTE. The only power cord rated for outdoor use is the standard cord included with the instrument (unless otherwise specified).

  • Page 81: Test Data Record Option

    This option provides the test data record obtained during the Performance Verification of the instrument and is limited to the primary characteristics of this instrument type. Option DE German language firmware Tektronix part number 160-8999-xx. Accessories Standard Accessories Internal Lead-gel Battery Assembly...
  • Page 82 Adapter, Direct Current 015-0327-00 Adapter, 50/75 W 017-0091-00 Adapter, 50/93 W 017-0092-00 Adapter, 50/125 W 017-0900-00 Interconnect Cable, 108 inch 012-0671-02 These adapters should be purchased if GR connectors (Tektronix part numbers 017-0063-00 and/or 017-0064-00) are purchased. 3–3 1502C MTDR User Manual...
  • Page 83 Options and Accessories 3–4 1502C MTDR User Manual...

  • Page 84: Appendix A: Specifications

    ±2 mr peak or less, filter set to 8 ±1 A Input Susceptibility Into diode clamps Distance Cursor Resolution 1/25th of 1 major division Cursor Readout –2 ft to ≥2,000 ft Range Resolution 0.004 ft A–1 1502C MTDR User Manual...
  • Page 85 Accuracy Included in total timebase error tolerance Custom Option Port Tektronix Chart Recorders YT–1 and YT–1S are designed to operate with the 1502C. Produces a high resolution thermal dot matrix recording of waveform and switch values. Line Voltage 115 VAC (90 to 132 VAC) 45 to 440 Hz Fused at 0.3 A...

  • Page 86: Environmental Characteristics

    Salt Atmosphere Withstand 48 hours, 20% solution without corrosion Sand and Dust Operates after test with cover on, non-operating MIL–STD–810, Method 510, Procedure I Washability Capable of being washed Fungus Inert Materials are fungus inert A–3 1502C MTDR User Manual...

  • Page 87: Certifications And Compliances

    CAT II Local-level mains (wall sockets). Equipment at this level includes appliances, portable tools, and similar products. Equipment is usually cord-connected. CAT I Secondary (signal level) or battery operated circuits of electronic equipment. (continued next page) A–4 1502C MTDR User Manual...

  • Page 88: Physical Characteristics

    Height 5.0 inches (127 mm) Width with handle 12.4 inches (315 mm) without handle 11.8 inches (300 mm) Depth with cover on 16.5 inches (436 mm) with handle extended to front 18.7 inches (490 mm) A–5 1502C MTDR User Manual...
  • Page 89 Appendix A: Specifications A–6 1502C MTDR User Manual...

  • Page 90: Appendix B: Operator Performance Checks

    Appendix B: Operator Performance Checks This appendix contains performance checks for many of the functions of the 1502C. They are recommended for incoming inspections to verify that the instrument is functioning properly. Procedures to verify the actual performance requirements are provided in the 1502C Service Manual.
  • Page 91 If the instrument fails this check, it must be repaired before any distance (Timebase) Check measurements can be made with it. 1. Turn the 1502C power on. The display should look very similar to Fig- ure B–1. 0.000 ft Figure B–1: Start-up Measurement Display 2.
  • Page 92 POSITION control, measure the distance to the rising edge of the waveform at the open end of the cable. The distance shown on the display distance window should be from 1.30 to 1.42 feet (0.396 to 0.433 m). B–3 1502C MTDR User Manual...
  • Page 93 10.000 feet (< 3.1 m). 10. Set the DIST/DIV control to .1 ft/div (0.025 m/div). 11. Turn the POSITION control counterclockwise until the distance window shows a distance of –2.000 feet (–0.611 m). B–4 1502C MTDR User Manual...
  • Page 94 Figure B–7: Waveform Off the Top of the Display 2. Using the POSITION control, verify that the entire waveform can be moved to the very bottom of the display (to the bottom graticule line). B–5 1502C MTDR User Manual...
  • Page 95 POSITION control and VERT SCALE control, set the gain to 5.00 mr/div. Keep the waveform centered vertically in the display. 3. Press MENU. 4. Using the POSITION control, select Diagnostics Menu. 5. Press MENU again. 6. Using the POSITION control, select Service Diagnostic Menu. B–6 1502C MTDR User Manual...
  • Page 96 1. In the Service Diagnostic Menu, select Sampling Efficiency and follow the directions on the screen. 2. When done with the test, press the MENU button repeatedly until the instrument returns to normal operation. B–7 1502C MTDR User Manual...
  • Page 97 1.744 ft Figure B–11: Rising Edge of Incident Pulse in Left-most Major Division 7. Using the POSITION control, move the cursor back to 0.000 ft (0.00 m). B–8 1502C MTDR User Manual...
  • Page 98 Figure B–12: Waveform Centered, Cursor at 0.000 ft 7. Risetime Check If the risetime is out of specification, it might be difficult to make accurate short-distance measurements near the front panel. 1. Set the 1502C front-panel controls: NOISE FILTER 1 avg VERT SCALE...
  • Page 99 Figure B–15: Cursor on Highest Major Graticule that Rising Edge crosses In the above example, the distances are –0.848 feet and –0.768 feet. The difference between these two measurements is 0.080 feet, which is well within specification. B–10 1502C MTDR User Manual...
  • Page 100 Using the Max Hold function (accessed in the Setup Menu, Acquisition Control) can simplify your observation of jitter. Max Hold allows you to observe the accumulated jitter without having to stare continuously at the display. –1.624 ft Accumulated Jitter Figure B–17: Jitter Captured Using Max Hold B–11 1502C MTDR User Manual...
  • Page 101 If you suspect a problem of this nature, you should have the instrument checked by a qualified service technician, using the diagnostics in the 1502C Service Manual. If the instrument passed all of the previous checks, it is ready for use.

  • Page 102: Appendix C: Operator Troubleshooting

    It is not an exhaustive set of tests that guarantee that the instrument meets all specifications and is perfectly calibrated. The calibration procedures in the 1502C Service Manual are the best method for assuring that the instrument meets all specifications.
  • Page 103 Perform initial operator performance verification checks. DO NOT USE INSTRUMENT. Serious problems need repair. Refer to 1502C Service Manual Troubleshooting procedures. Did instrument pass checks? Refer to Option Port and Accessories Troubleshooting procedure. Replace fuse. If no accessories, then OK to use instrument.

  • Page 104: Error Messages

    If the error is in response to another Option Port device, remove that device. If the error ceases, have the device serviced. If the error persists, have the TDR serviced. Message: ERROR: Acquisition Initialization TYPE: Pulse gap > 3.75 dB C–3 1502C MTDR User Manual...
  • Page 105 Have the instrument repaired. If a pulse is present, distance measurements can be made. If the pulse is more than two divisions high, the millirho scale is not calibrated and loss measurements should not be made. Message: ERROR: Acquisition Initialization TYPE: Vertical Scale failure C–4 1502C MTDR User Manual...
  • Page 106 This message can occur at power on initialization only. These are common error messages because they are triggered by many kinds of failures and come from one of the very first routines that the instrument executes. They are usually fatal C–5 1502C MTDR User Manual...
  • Page 107 This could be because the pulse is not there, or because the sampler or gain circuitry is broken, or even because the timebase is not function- ing properly. Remedies: The instrument must be sent to service for repair. C–6 1502C MTDR User Manual...

  • Page 108: Appendix D: Application Note

    Using the Tektronix Time-Domain Reflectometry Slide Rule Most people who make quantitative reflectometry tests or measurements should find the Tektronix TDR Slide Rule helpful. Those new to the subject will find the slide rule graphically summarizes a wealth of information on reflectometry.

  • Page 109: Relationships

    Figure D–1: Slide Rule of VSWR vs. Percent Reflected Voltage On the upper scale, locate the known value of VSWR (or %). Adjacent to that point is the corresponding value for % (or VSWR). VSWR is the peak-to-valley ratio of standing sine waves. D–2 1502C MTDR User Manual...

  • Page 110: Return Loss (Db) Vs. Percent Reflected Voltage

    As with measurements on VSWR, there is only a simple mathematical relation- ship between reflection measurements using sine waves and reflection measure- ments using pulses when one resistive discontinuity is the whole cause for the sizable reflections. D–3 1502C MTDR User Manual...

  • Page 111: Percent Reflected Voltage Vs. Characteristic Line Impedance

    The risetime or amplitude of received reflections may be signi- ficantly degraded or attenuated by two-way losses of the line . +1r = ∞ W +.03r = 53.1W Figure D–3: Slide Rule 50 ohm Source D–4 1502C MTDR User Manual...
  • Page 112 For best accuracy, select the scale farthest to your right in which the impedance level of interest is in view. Read from the adjacent stationary scale the reflection coefficient or percent reflected voltage that corresponds to the Ohms selected. D–5 1502C MTDR User Manual...

  • Page 113: Percent Reflected Voltage Vs. Load Resistance

    TDR display. The impedance (Ohms) causing the reflection can then be read from the sliding scale by noting the position on the fixed scale that corresponds to the position of the reflection on the TDR display. D–6 1502C MTDR User Manual...

  • Page 114: Centimeters Vs. Inches Or Meters Vs. Feet

    METERS, then reading the distance in feet next to the point of the arrow labeled FEET. Likewise, feet are converted to meters using these directions in reverse. D–7 1502C MTDR User Manual...

  • Page 115: Dielectric Constant Vs. Velocity Factor

    If the distance to or between faults is known and you want to find the time or velocity factor, set the distance under the appropriate arrow first, then read the answer on the ROUND TRIP TIME scales. D–8 1502C MTDR User Manual...

  • Page 116: Time Vs. Long Distances, In Meters Or Feet (Any Dielectric

    1.0 1.5 2.0 3 4 5 6 Polyethylene CONSTANT ROUND Time = 300 ns 00ns 150ns 200ns 300ns 500ns 700n TRIP TIME Velocity Factor = .66 VELOCITY FACTOR .8 .7 Figure D–8: Dielectric Constant and Velocity Factor, Long Distance D–9 1502C MTDR User Manual...
  • Page 117 Appendix D: Application Note D–10 1502C MTDR User Manual...

  • Page 118: Glossary

    Any condition that makes the cable less efficient at delivering electrical energy than it was designed to be. Water leaking through the insulation, poorly mated connectors, and bad splices are typical types cable faults. Capacitance (see Reactance) Glossary–1 1502C MTDR User Manual...
  • Page 119 DC signals. Technically, impedance is a function of the frequency of the electrical signal, so it should be specified at a frequency. As a practical matter, the impedance of most cables changes very little over the range of frequencies they are designed for. Glossary–2 1502C MTDR User Manual...
  • Page 120 0 to +1, and a load or fault with a lower impedance will return a rho measurement of 0 to –1. The scale for rho measurements is determined by the height of the incident pulse. A pulse two divisions high Glossary–3 1502C MTDR User Manual...
  • Page 121 Resistance is the low (or zero) frequency part of impedance. Resolution For a given parameter, the smallest increment or change in value that can be measured, generated, or displayed. Glossary–4 1502C MTDR User Manual...
  • Page 122 Unless otherwise specified, the period of time is assumed to be the calibration interval (might also apply to range, resolution, or precision as a function of time). The term stability might also be used to Glossary–5 1502C MTDR User Manual...
  • Page 123 (so it is always a number between 0 and 1). A velocity of propagation value of 0.50 indicates that the electrical energy moves through the cable at half the speed of light. Waveform Averaging (see Noise) Glossary–6 1502C MTDR User Manual...
  • Page 124 BNC to GR, 3–2 Horizontal Set Reference, 1–24, 2–13 BNC to Hook Tips, 3–2 HORZ SET REF (see Horizontal Set Reference), 2–13 BNC to N Type, 3–2 Humidity Spec, A–3 BNC to UHF, 3–2 Contacting Tektronix, x Index–1 1502C MTDR User Manual...
  • Page 125 Backlight, 1–9 Charging, 1–2 Distance / Division, 1–9 Cords, 3–1 Maximum Hold, 1–9 Safety, xii Pulse, 1–9 Fuse, xii, 1–2 Fuse Rating, 1–2 Single Sweep, 1–9 Requirements, viii Vertical Scale, 1–9 Single Sweep, 1–31 Safety, xii Index–2 1502C MTDR User Manual...
  • Page 126 Short, 1–15, 2–4, 2–19 Single Sweep, 1–31, 2–24 Water Resistance Spec, A–3 Slide Rule, 3–2 Waveform Storage, 1–20 Specifications, A–1 Web site address, Tektronix, x Electrical, A–1 Weight Spec, A–4 Environmental, A–3 What is a 1503B?, 2–1 Index–3 1502C MTDR User Manual...
  • Page 127 Index Index–4 1502C MTDR User Manual...

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