$C3100 "AUTO TRACKER" Automatic Waveform & Circuit Analyzer Operation and Application Manual S=NCORE 3200 Sencore Drive, Sioux Falls, South Dakota 57107DESCRIPTION INTRODUCTION ‘The SC3100 “AUTO TRACKER™” Waveform and Cireuit Analyzer offers a whole new concept in electronic test equipment. It provides all of the measurements you need to completely analyze a waveform or circuit faster, and more accurately than with any other unit, ‘There are other “digital” oscilloscopes that provide a digital readout of the signal displayed on the seope CRT. But these units fall short of the waveform analyzing capabilities of the SC3100 in two very important areas: ease of use and accuracy. Other digital scopes only do the graticule counting for you. You must still properly lock in the waveform and obtain a CRT display. Then you need to find the menu that contains the measurement you want and select, the measurement channel before you can begin to take a reading. Both the input coupling and horizontal and vertical verniers must be set correctly ‘to make the reading. Many other digital oscilloscopes FEATURES The $C3100 “Waveform & Circuit Analyzer” begins with a full feature, high performance, dual trace oscilloscope. It has a 100 MHz bandwidth, useable to 120 MHz, to accurately view digital signals. The input extends from a 2 mV sensitivity direct input, to a ‘maximum of 2000 volts with the supplied probes, ‘The sync circuits are streamlined to just four user controls, yet they provide “rock solid” triggering on all signals. Sync separators provide solid trigger lock on complex video waveforms. Special circuits remove the half-line shift when viewing a line of interlaced video to prevent vertical syne ghosting. Conventional oscilloscope measurements are greatly enhanced with two types of digital waveform analyzing tests. The Auto-Tracking™ digital tests measure the frequency, DCV or AC voltage of the applied signal independently of any CRT control setting. You can select between peak-to-peak, average RMS, or dBm (1 milliwatt into 600 ohms reference) AC voltage readings. The Auto-Tracking™ measurements automatically follow any changes in the input signal. Exclusive Delta measurements allow you to analyze the time, frequency and amplitude of any portion of the waveform. A Delta DCV test automatically even require you to adjust cursors to the area of the signal you want to measure. On top of all this, the measurements are still based on the inaccurate analog CRT circuits and user interpretation, and may have errors of 15% or more. Unlike conventional analog oscilloscopes and other digital scopes, the SC3100 “AUTO TRACKER™” allows you to measure all waveform parameters at the push of a button, without time consuming setups, graticule counting or cursor setting. For most measurements the waveform doesn't even need to be displayed on the CRT. All of measurements are made by digital circuits that are independent of the CRT circuitry, for virtually error-free measurements. ‘The “AUTO TRACKER™" also includes ohms, current, and continuity tests to analyze and track down problems in the whole circuit. It is a complete waveform and circuit analyzer. determines the absolute DC level of any waveform point referenced to ground to confirm proper logic levels or analyze trip points. All of the Auto-Tracking™ and Delta measurements are made through the same probe that applies the signal to the CRT display, The measurements are unaffected by the vertical and horizontal vernier and position controls. Because all of the waveform measurements are made using digital circuits that are separate from the analog CRT circuits, the readings are many times more accurate and faster than conventional oscilloscope measurements, Measure DC current up to 2 amps with minimal voltage burden. The ohmmeter is fully autoranged for resistance measurements up to 100 megohms. A special Continuity Test provides a near-instaneaous audible continuity indication for fast circuit tracing. ‘These tests are made through an input that is separate from the oscilloscope input to prevent accidental measurement errors and to keep high currents away from the sensitive scope input. The functions are fuse protected against overload. Auto-Tracking and "AUTO TRACKER™ are trademarks of SENCORE INC.SPECIFICATIONS Analog CRT Section Vertical Amplifier DISPLAY MODES: Channel A, inverted channel AGA), channel B, dual trace (A&B), algebraic sum (A+B) or difference (B-A), vector (X-¥) INPUT COUPLING MODES: AC, DC, and ground. CALIBRATION ACCURACY: =4% at 1 kHz, 15-35° C for channel A and/or B; 23% for A+B or B.A modes. FREQUENCY RESPONSE (100 MHz): AC coupled: +£34B of 1 kHz level from 10 Hz to 100 MHz, useable to 150 MHz. DC coupled: =34B of 1 kHz level from DC to 100 MHz, useable to 150 MHz BANDWIDTH Switch: Reduces frequency response to 20 MHz = 5 MHz = 348. DEFLECTION FACTORS: 13 calibrated ranges in 1- 2-5 sequence, plus Autorange. ORT is calibrated to read direct with supplied 396292 10X Probe, Vernier continuously variable between ranges with detent for calibrated position. Autorange position automatically selects attenuator range (based on digital peak-to-peak meter) to show approximately 2-4 divisions of waveform amplitude. SENSITIVITY: 20 mV/div. to 200 Vidiv. with supplied 396292 10X probe; 2 mVidiv. to 20 Vidiv. with (optional) DP270 Direct Probe. INPUT IMPEDANCE: 10 megohms shunted by 15 pF with 396292 10X Probe; 1 megohm shunted by 20 pF direct. MAXIMUM MEASURING VOLTAGE: Supplied '39G292 probes: 2000 volts (DC + Peak AC) vernier uncalibrated, 1600 volt vernier calibrated. Direct: 200 volts (DC + Peak AC) with vernier uncalibrated, 160 volts vernier calibrated. Derated for frequencies above 1 MHz MAXIMUM INPUT PROTECTION: Supplied 996292 10X Probe: 2500 volts breakdown (DC + Peak AC), Direet: 400 volts (DC + Peak AC). Derated for frequencies above 850 kHz. CHANNEL ISOLATION: >58 dB 0-100 MHz ‘TIME DELAY: Both channels delayed to show trigger point. DUAL TRACE: Dual chop automatically selected for timebase settings of 100 to .2 mSec in “A&B” mode. Pushing “A” and “B” buttons simultaneously selects alternate display mode. VECTOR: Channel A is Y axis, channel B is X axis, Bandwidth: #8 dB DC to 2 MHz. Phase shift: =3° from 10 Hz to 200 kHz. Sensitivity: Same as vertical amplifier. Horizontal Sweep: ‘TIMEBASE RANGES: 21 calibrated sweep rates in 1- 2.5 sequence, plus Autorange, TVV and TVH. Vernier continuously variable between 1-2-5 steps, with detent for calibrated position. SWEEP RATES: 100 milliseconds/division to 20 nanosecond/division. Autorange automatically selects sweep rate to show approximately 2 cycles of waveform, based on digital frequency counter reading. ACCURACY: +3%, VIDEO PRESETS: Automatically displays 2 horizontal lines (TVH) or 2 vertical fields (TVV) of standard NTSC composite video signal. TV trigger mode is automatically selected. 10X EXPAND: Expands horizontal sweep 10 times. Activated by pulling horizontal position control. Accuracy: =5%. ‘Trigger Circuits: ‘TRIGGER SOURCE: CH A, CHB, AC power line, or external ‘TRIGGER MODES: NORM: provides trace only when triggered, AUTO: provides trace at all times. TV: same as AUTO with syne separators added to trigger on vertical or horizontal syne pulses, vertical syne selected for all “msec” sweep rates, horizontal syne selected for all “usec” sweep rates. TV mode is automatically selected in video presets, ‘TRIGGER POLARITY: Selectable between + and - waveform transition for non-video sigmals. Selects positive or negative syne on video signals. LEVEL SENSITIVITY: Maximum of 0.5 divisions of CRT deflection for frequencies 10 Hz. to 50 MHz. AC coupled; maximum 1 division of CRT deflection for frequencies 50 MHz to 100 MHz AC coupled, increasing to 3 divisions at 120 MH TRIGGER BANDWIDTH: DC to 120 MHz in 100 ‘MHz bandwidth; DC to 20 MHz in 20 MHz bandwidth. EXTERNAL TRIGGER SENSITIVITY: 200 millivolts pk-to-pk to 100 MHz, triggerable to 120 MHz ‘Maximum input: 500 volts (DC + Peak AC). 2™ Digital Tests DCV FUNCTION: Provides direct reading of DC voltage on selected channel. Reading unaffected by INPUT COUPLING, vertical attenuator or other scope controls, ARS ee eseee ceSpecifications Continued 2 _______ RANGES and RESOLUTION: Four ranges automatically selected; 0.001 to 1.999, 2.00 to 19.99, 20.0 to 199.9, 200 to 1999. Direct reading, with supplied 396292 10X Probe, supplied 89295 DC Voltage Probe, or optional DP270 Direct Probe. ACCURACY: #0.5% #2 digits using supplied 396292 10X probes; <0.5% between channels. INPUT IMPEDANCE: 15 megohms through supplied 396292. 10X probes and 89G295 DC Voltage Probe; 1.5 megohms direct input. MAXIMUM INPUT PROTECTION: 2500 volts breakdown (DC + Peak AC) with supplied 396292 10X Probes; 400 volts (DC + Peak AC) direct. Peak-to-Peak Volts: VPP FUNCTION: Provides direct reading of peak-to- peak voltage on selected channel with either X10 or direct probes. Microprocessor controlled successive approximation to determine + and - peaks. DC coupled, 26 approximations per reading, worst-case. Reading unaffected by ‘Trigger and Timebase controls. RANGES and RESOLUTION: 4 ranges determined by channel A or B input attenuator setting (unaffected by vertical vernier); 0 to 8, 8 to 80, 80 to 800, 800 to 2000 volts with supplied 39G292 10X Probe. ACCURACY: 42% +4 counts including probes at 1 kHz; <2% between channels at 1 kHz FREQUENCY RESPONSE: +0.5dB from 20 Hz to 30 ‘MHz, 14B from 30mHz to 50 mHz,<-34B at 100 ‘MHz in 100 Bandwidth; +0.54B from 20 Hz to 10 ‘MHz in 20 MHz Bandwidth. MAXIMUM INPUT PROTECTION: Same as analog CRT section. AC Volts: ACV FUNCTION: Calculates RMS sinewave value from PPV measurement. (.707xpeak) Direct readout of selected A or B channel with either X10 or direct probes. Reading unaffected by Trigger and Timebase controls. RANGES and RESOLUTION: 4 ranges determined by channel A or B input attenuator setting (unaffected by vertical vernier); 0.001 to 707 volts with supplied 39292 10X probe. ACCURACY: Same as PPV function on a 1 kHz FREQUENCY RESPONSE: Same as PPV function (sinewave applications only). MAXIMUM INPUT PROTECTION: Same as analog. CRT section. dBm: dBm FUNCTION: Caleulates dBm measurement from PPV sinewave measurement, referencing 1 mW across 60082 (0 dBm =.7746 volts RMS). Direct readout of selected A or B channel with either X10 or direct probes. Reading unaffected by ‘Trigger and Timebase controls, RANGES: 4 determined by channel A or B input attenuator setting (unaffected by vertical vernier); -60 to 59.2 with supplied 39G295 10x. probe. RESOLUTION: 2 or 3 digits depending on level: 1 4B for levels less than -15 dBm, .1 dB for levels -15, dBm or greater. ACCURACY: Same as PPV function on a 1 kHz, FREQUENCY RESPONSE: Same as PPV function (sinewave applications only). MAXIMUM INPUT PROTECTION: Same as analog CRT section. Frequency: FUNCTION: Automatically displays the frequency of the signal on selected channel. Main channel (determined by “Trigger Source”) uses trigger circuit, auxiliary channel counts input signal directly. RANGES & RESOLUTION: 7 ranges automatically selected; 10.00 to 99.99 Hz, 100.0 to 999.9 Hz, 1.0000 to 99.999 kHz, 100.000 to 999.999 kHz, 1.00000 to 9.99999 MHz, 10,0000 to 99.9999 MHz, 100.000 to 150 MHz. ACCURACY: .001% +1 digit over operating temperature range; Aging: <.001% per year. SENSITIVITY: Main channel: same as trigger circuits, except 1.5 division maximum in.02 volts/div. range for frequencies below 100 MHz, Auxiliary channel: 1.5 division of deflection for all frequencies. SOURCE: Selected with channel A or B push button. Microcomputer automatically selects between trigger circuit output or auxiliary counter amplifier, depending on “Trigger Source” switch setting, READ RATE: <.5 seconds for all frequencies 10 Hz to 150 MHz, Delta Digital Tests All Tests: FUNCTION: The Delta tests allow measurements of a portion of the displayed waveform. All readings are directDELTA MEASUREMENT BAR (all tests except Delta DC): Delta Begin and Delta End controls set intensified area to any portion of waveform. Function of controls automatically reverses if ends of bar are overlapped. SETABILITY: 5 ns typical. Delta Peak-to-Peak: FUNCTION: Measures amplitude of intensified area ‘on selected channel, RANGE AND SPECIFICATIONS: Same as Peak-to- Peak function. Delta Time: FUNCTION: Measures time of intensified waveform portion, ACCURACY: Same as frequency counter function, Dependant on user setting of Delta Begin and End controls. RANGE: 6 nsec to 1 second. Automatic decimal placement and “mS” or “uS” annunciator reading. Delta Frequency: FUNCTION: Converts Delta Time reading to equivalent frequency. ACCURACY: Same as Delta Time function. RANGE: 1 Hz to 200 MHz. Automatic decimal placement and Hz, kHz, or MHz annunciator reading. Delta DC Volts: FUNCTION: Measures DC voltage level of marked waveform point in respect to ground using the PPV and DCV functions. MARKER: Fully adjustable over entire range of ‘waveform with “Delta DC/Delta End” control. RANGES and RESOLUTION: Same as VPP funetion. ACCURACY: Better than 2.5% +5 digits at 1 kHz using supplied 39G292 10X Probe. FREQUENCY RESPONSE: +.5dB 20 Hz to 10 MHz. Circuit Parameter Tests: Ohms FUNCTION: Provides in- or out-of-cireuit ohms and continuity test through OHMS/CURRENT INPUT Jacks, RANGES and RESOLUTION: 5 ranges, automatically selected; 0.00 to 210 £2, 200 to 21.0 KO, 20.0 k@ to 2.1 MO, 2.00 MQ to 11.00 Ma, 10 ‘MA to 100 MQ. ACCURACY: 0.2% +2 digits except 0.5% £8 digits 2.00 MQ to 100 MQ range. MAXIMUM TEST CURRENT: 1 mA. MAXIMUM TEST VOLTAGE: 200 mV in the 3 lowest ranges; 2 volts in top two ranges INPUT PROTECTION: Fuse protected; 1500 volts (DC + Peak AC) between input jack and from either jack to chassis. Continuity Test: FUNCTION: Provides audible tone of continuity. RANGE: 0 to 210 Q. Audible tone turns on if resistance is <10Q and turns off if resistance is 315.0, +20, DC Current: FUNCTION: Provides measurement of DC current through OHMS/CURRENT INPUT Jacks. RANGES and RESOLUTION: 5 ranges, automatically selected: .001 to 1.99 mA, 2.00 to 19.99 mA, 20.0 to 199.9 mA, 200 to 999 mA, 1.00 amp to 1.99 amp. ACCURACY: 0.3% +2 digits. VOLTAGE BURDEN: <1.5 volts at 2 amps; <750 mV typical for currents below 1 amp. OVER VOLTAGE PROTECTION: 1500 volts (DC + Peak AC) between input jack and from either jack to chassis with internal high voltage fuse. OVER CURRENT PROTECTION: 2 A, 250 volt. externally-accessible fuse and 3 A, 600 volt internal fuse. Digital Display: TYPE: 6-digit liquid crystal, fast response time and high contrast with back lighting. ANUNCIATORS: Automatically controlled for each function, with channel indicator preceding readout when required CRT Display: SIZE: 96.4 x 120 mm, ‘TYPE: High sensitivity and brightness with GH (P31 blue-green) phosphor. ACCELERATING VOLTAGE: 14 kV to match CRT requirements. GRATICULES: 8 x 10 grid internally etched on CRT faceplate with 0, 10, 90, and 100% markings. BEAMFINDER: Disables trigger and intensity controls, and reduces vertical and horizontal gain to locate beam,Specifications Contin wed SAA ‘Optional: WARM UP TIME: Unit completely operational as soon as CRT trace appears. Fully meets ‘1B72 IEEE 488 Interface Accessory specifications after 20 minutes. 1B78 RS232 Interface Accessory OPERATING TEMPERATURE: -10° to 45° C (14° to HP200: 50 KV High Voltage Probe 113° F) PL207: RF Pickup Loop, ‘TP212: 10 KV Transient Protector Probe PC269: Protective Cover DP270: 1:1 Direct Probe 39G81A: 250 MHz Demodulator Probe 39G303: Probe Accessory Kit CASE: Vinyl-clad aluminum. Full EMI shielding. SIZE: 7.25" x 13.75" x 15” HWD (18.4 x 34.9 x 38.1 WEIGHT: 25 Ibs (9.33 kg.) POWER: 105-125 VAC 50/60 Hz. Factory convertible to 210-250 VAC 50/60 Hz operation. POWER CONSUMPTION: 80 watts maximum. Accessories: Supplied: 2 ea: 396292 10X Low Capacity probe with 5” ground, 12” ground and retractable tip. 1 ea: 396295 DVM Test Leads. 1 ea: 39G331 10X Probe Accessory Kit containing: ID bands (2 yellow, 2 red), Ground Insulator Ring (2) Covered by Patents #4,473,857, #4,564,805 and 4,323,972 ‘Specifications subject to change without notice.Fig. 1 - Front panel controls and feature. CONTROLS 1. DIGITAL READOUT - Provides a readout of any of the DELTA MEASUREMENTS (5), OHMS/DC AMPS (7), CHANNEL A DIGITAL TESTS (9) or CHANNEL B DIGITAL TESTS (11) functions. The correct decimal placement and annunciators to indicate the channel, function, and range are automatically displayed, 2. FOCUS - Adjust for sharpest trace on CRT DISPLAY (37). 8, INTENSITY - Determines brightness of CRT trace. 4, DELTA MARKER Controls - Use with the DELTA MEASUREMENTS Buttons (5) to position the intensified Delta Measurement Bar on the waveform. a & b. BEGIN & END - Controls automatically exchange function if the Delta Bar end is positioned before the beginning. b. END/ADCV - Adjusts the intensified point when the Delta DCV functions are selected Ge&f. cena, 8 wala), 5. DELTA MEASUREMENTS - Selects the parameter that is measured by the Delta Bar. Readings are displayed in the DIGITAL READOUT (. a. CHAAPPV- Measures the peak-to-peak voltage of the intensified portion of the channel A waveform, b. CHB APPV- Measures the peak-to-peak voltage of the intensified portion of the channel B waveform. ©. TIME - Measures the time duration of the Delta Bar for either the channel A or channel B waveform. d. AFREQ - Converts the time duration of the Delta Bar to the approximate frequency. e. CHADELTA DCV - Measures the instantaneous voltage to ground of the intensified point on the channel A waveform. Use with the DELTA DC MARKER Control (5b), £ CHB DELTA DCV - Measures the instantaneous voltage to ground of the intensified point on the channel B waveform. Use with the DELTA DC MARKER Controls (5b).Controls Continued 6. TIMEBASE - Sets the sweep speed at which the CRT beam moves horizontally across the CRT. Controls do not affect the digital measurements. a. TIME/DIV - Selects the time value for one major CRT division b. VERNIER - Allows the sweep speed to be varied within the major steps selected by the TIME/DIV Control. ¢. AUTO - Allows the microprocessor to automatically select the sweep speed needed to display 2 to 5 eyeles. @. TVV VIDEO PRESET - Displays two vertical fields of composite video and automatically selects video syne separators, . TVH VIDEO PRESET - Displays two horizontal lines of composite video and automatically selects video syne separators 7. OHMS/DC AMPS - Use with the OHMS/DC AMPS INPUT (27) and DVM TEST LEADS (43) to ‘measure cireuit parameters. Readings are displayed in the DIGITAL READOUT (1). a. OHMS - Select to measure resistance values up to 100 megohms. b. CONT TEST - Provides a near-instantaneous audible tone indication of continuity and digital readout of resistance values to 2100. DC AMPS - Select to measure DC current. d. OHMS ZERO - Push when either the OHMS, or CONT TEST (7a or b) is selected and the test leads are shorted together to zero out the internal and test lead resistances. 8, HORIZ POSITION/1OX EXPAND Control - Use to adjust the horizontal position of the CRT trace. Pull to expand the CRT display horizontally by a factor of 10. 9. CHANNEL A AUTO-TRACKING TEST Buttons = Selects the measured parameter of the waveform applied to the CH A INPUT Jack (24). DCV - Measures the average DC voltage. VPP - Measures the peak-to-peak voltage. FREQ - Measures the frequency. ACV - Measures the RMS AC voltage. dBm - Measures the dBm voltage level. 10. VERTICAL POSITION (CH A) - Determines vertical position of the channel A trace. Pull knob to invert the polarity. 11. CHANNEL B AUTO TRACKING TESTS - Selects the measured parameter of the waveform applied to the CH B INPUT Jack (22). DCV_ - Measures the average DC voltage. VPP _ - Measures the peak-to-peak voltage. FREQ - Measures the frequency ACV - Measures the RMS AC voltage. dBm - Measures the dBm voltage level 12, INVERT BAL - Calibrates the channel A invert. amplifier for the same DC reference level for inverted and noninverted displays. 13. VERTICAL POSITION (CH B) - Determines the vertical position of the channel B trace. 14, VERT BAL (Channels A & B) - Calibrates the input circuits for the same DC reference level for each setting of the VOLTS/DIV switch, 15. VOLTS/DIV (CH B) - Selects the vertical deflection factor for the channel B CRT waveform display and the range for the VPP readings. a. VOLTSIDIV Control - Sets the voltage value for one major CRT division. b. VERTICAL VERNIER - Allows the vertical deflection to be varied within the major steps selected by the VOLTS/DIV Control. Does not affect the digital measurements. ¢. AUTO - Allows the microprocessor to automatically select the VOLTS/DIV range needed to display 2 to 4 divisions of deflection 16. VOLTS/DIV (CH A) Selects the vertical deflection, factor for the channel A CRT waveform display and the range for the VPP readings. a, VOLTS/DIV Control - Sets the voltage value for one major CRT division. b, VERTICAL VERNIER - Allows the vertical deflection to be varied within the major steps selected by the VOLTS/DIV Control. Does not. affect the digital measurements, . AUTO - Allows the microprocessor to automatically select the VOLTS/DIV range needed to display 2 to 4 divisions of deflection, 17. BANDWIDTH (CH B) - Determines the bandwidth of the signal applied to the CRT, digital meter, and trigger circuits from the CH B INPUT ack (22). 18. BANDWIDTH (CH A) - Determines the bandwidth of the signal applied to the CRT, digital meter, and trigger circuits from the CH A INPUT ack (24).19. INPUT COUPLING (CH B) - Selects DC or AC. input coupling, or ground reference of the signal applied to the CH B INPUT Jack (22). 20. INPUT COUPLING (CH A) - Selects DC or AC input coupling, or ground reference of the signal applied to the CHA INPUT Jack (24). 21. DCV Jack (CH B) - Input routes DC signals around the channel B INPUT COUPLING switch (19) to allow DC measurements while CRT is AC coupled. 22, CH B INPUT Jack - Supplies signals for all channel B tests except DCV. 28. DOV Jack (CH A) - Input routes DC signals around the channel A INPUT COUPLING switch (20) to allow DC measurements while CRT is AC coupled. 24, CH A INPUT Jack - Supplies signals for all channel A tests except DCV. TRIGGER SOURCE - Selects signal source that is used to trigger the sweep circuits. a. CHA. Selects the signal applied to the CHA INPUT (24. b. CHB - Selects the signal applied to the CH B INPUT (22). ¢ AC LINE - Locks the trigger circuits to the 60 Hz AC line. 4. EXT Selects the signal applied to the EXT ‘TRIGGER INPUT Jack (29). 26. TRIGGER LEVEL - Determines the amplitude of the input signal that triggers the trigger cireuits. The trigger circuits will trigger at the center of a symmetrical waveform when set to “0”. The “+” and “ areas indicate amplitude change only, not trigger polarity, 27. OHMS/DC AMPS INPUT - Provides a connection for the DVM TEST LEADS (43) to make ohms and DC current measurements, 28. TRIGGER MODE - Selects three different options for triggering the waveform. a. NORM- Produces a trace only when the triggering circuits are locked to the incoming signal selected by the TRIGGER SOURCE switch (25). b. AUTO - Produces a trace at all times. c. TV- Selects special syne separators to trigger on the syne pulses of composite video signals. Automatically selects vertical syne for “msec” sweep speeds and horizontal syne pulses for “see sweep speeds. 29. EXT TRIG INPUT Jack- Allows an external trigger signal to be used when the TRIGGER SOURCE switch (25) is set to “EXT”. 30. TRIGGER POLARITY - Sets the trigger circuits to trigger on either the positive (+) or negative (-) transition of the incoming signal. The polarity refers to the syne pulse polarity of video signals 31. PULL CHART - Provides simplified operation, instructions, 82. PROBE COMP - Provides a square wave signal for compensating the 10X LOW CAPACITY PROBES (42). 33. GROUND Jack - Provides a connection to use the black DVM TEST LEAD (43) for grounding and DC measurements. To prevent waveform distortion do not use as the signal ground when measuring signals greater than 100 kHz. 34, TRACE ROTATOR - Electrically positions the trace to compensate for different magnetic field conditions. Adjust so that the CRT trace is parallel to the horizontal lines etched on the CRT. 35. CRT DISPLAY MODE Buttons - Use to select, the trace display mode on the CRT. a. CHA Displays a single trace of the CH A INPUT (24), Press together with CH B Button for A & B dual alternate display. b. CHB - Displays a single trace of the CH B INPUT (22), Press together with CH A Button for A & B dual alternate display. ¢. A&B Displays both the channel A & B traces. Dual chop display is selected when the TIMEBASE TIME/DIV Control (6a) is set between 100 and .1 msec. Dual alternate operation occurs between 50 and .02 j.sec. Select dual alternate mode for slower sweep rates by pushing the CH A and the CH B CRT DISPLAY MODE Buttons simultaneously. 4. A+B ADD - Provides a single trace display showing the algebraic sum of the CH A and CH B input signals, ¢,_X-¥ VECTOR - Selects X-Y operation. The CH A INPUT Jack (24) provides vertical deflection and the CH B INPUT Jack (22) provides horizontal deflection. {. BEAM FINDER - Press to locate the relative position of the trace(s) 36. POWER - Push in to apply AC power; push and release to remove power.Controls Continued 37. CRT DISPLAY - Provides a waveform display of the signal applied to the CH A INPUT (24) or CH B INPUT (22). REAR PANEL FEATURES, 38, OHMS PROTECTION FUSE - Protects the unit from damage due to external voltage or current applied to the OHMS/DC AMPS Input (27) when the ohms function is selected. Replace only with 1/8 amp, 3AG 250 volt Fast-Blo fuse. 39, DC AMPS PROTECTION FUSE - Protects unit from damage due to currents greater than 2 amps applied to the OHMS/DC AMPS Input (27). Replace only with 2 amp, 3AG 250 volt Fast-Blo fuse. id Fig. 2-$C3100 rear panel features 40. AC LINE FUSE - Protects unit from damage due to internal problems which cause excessive current draw. Replace only with 1 amp, 3AG, 250 volt Slo-Blo fuse. 41, INTERFACE ACCESSORY Jack - Provides connection for the optional IB72 IEEE 488 INTERFACE BUS Accessory (53) or IB78 RS232 INTERFACE Accessory (64).SUPPLIED ACCESSORIES 42, 10X LOW CAPACITY PROBES (396292) (2 supplied) - Use to apply signals for reading on CRT or digital readout. Connect BNC connector to the CH A or CH B INPUT Jacks (22 or 24) and mini banana connector to DCV IN Jacks (21 and 23). _ 43, DVM TEST LEADS (396295) - Connect to OHMS/DC AMPS INPUT Jack to make ohms and DC current measurements. Also use black lead to connect to GROUND Jack (33) when an extra earth ground connection is needed. 44, PROBE ACCESSORY KIT (39G331) Includes 2 ~ yellow and 2 red Probe ID Bands and 2 Ground Ring Insulators. OPTIONAL ACCESSORIES _45. HP200 50 kV HIGH VOLTAGE PROBE - Use with the (optional) DCV PROBE (50) to extend the DCV measuring range to 50 kV. 46. PC269 PROTECTIVE COVER - Snap-on cover protects front panel and provides test probe storage. 47. PL207 RF PICKUP LOOP - Used for inductive pickup of signals when peak-to-peak voltage is not important. 48. TP212 10 kV TRANSIENT PROTECTOR PROBE - Use with (optional) DCV PROBE (50) to extend the DCV measuring range to 10 kV. 49, DP270 1:1 DIRECT PROBE - Provides direct, input for measuring signals in the 5 to 50 millivolt range and frequencies up to 15 MHz. = 50. DCV PROBE (396157) - Allows DC voltages to be measured separately from the 396294 Low Capacity Probes. Connect to DCV Jacks (21 & 23). 51, 250 MHz DEMODULATOR PROBE (39GB1A) - Shows the detected envelope of an AM modulated signal up to 250 MHz. ~ 52. PROBE TIP ACCESSORY KIT (39G303) - Includes accessories to use with the supplied 39G292 10X LOW CAPACITY PROBES (42), or the (optional) DP270 1:1 DIRECT PROBE (49). Includes: * Ground Bayonet Small alligator clip * BNC adapter + IC Leg isolator * Mini-Grabber (red) _* Long Needle point clip * Mini-Grabber ground lead adapter Fig. 3- $C3100 Supplied accessories 58. IB72 IEEE 488 INTERFACE BUS Accessory - Connects between the INTERFACE ACCESSORY Jack (41) and the IEEE 488 port of a bus controller to allow the SC3100 to be used in an IEEE system. 54. IB78 RS232 INTERFACE Accessory - Connects between the INTERFACE ACCESSORY Jack (41) and the RS232 port of a controller to allow the 'SC3100 to be used for automated testing, Fig. 4 $C3100 Optional accessoriesOPERATION INTRODUCTION ‘This portion of the manual explains how to prepare the SC3100 for operation and describes how to use its controls and features. It contains the following major sections for easy reference; 1)Preparation For Use, 2)Applying Signals To The Input, 3)Setting The Vertical Display, 4)Setting The Trigger Circuits, 5)Setting The Horizontal Display, 6)Using The CRT Display, 7)Using The Auto-Tracking Digital Functions, 8)Using The Delta Measurements, 9)Using The Circuit Parameter Tests, and 10)Computer Automated Operation ‘The operation of the SC3100's CRT display section is identical to that of a standard analog oscilloscope. The vertical and horizontal controls are calibrated to PREPARATION FOR USE ‘The SC3100 is ready to use when it is removed from its packing material and connected to a proper source of AC power. All of the supplied accessories are in the same box as the SC3100. When you first unpack the “AUTO TRACKER”, confirm that you have received all of the supplied accessories listed on page 10. If any are missing, promptly notify the Sencore Service Department at the address and phone number located inside the back cover. Place the C3100 in a convenient location that is within about 24 inches of the equipment that you will be servicing. This will provide adequate work area, while keeping the equipment close enough to connect the test probes. Do not block the air vents located on the top, bottom and sides of the case. Allow at least 3 of space at the rear of the unit for air to circulate around the heat sink. CAUTION Position the SC3100 to allow proper air circulation. Allow 3 inches of space behind the rear panel heat sinks. ‘The $C3100 is equipped with two tilt bails located on the front feet. These tilt bails allow the front of the unit to be raised by approximately 4” when the unit is ‘used on a bench top. The tilt bails may be moved to the rear feet to allow the rear of the unit to be u allow CRT analog measurements of signals when desired Most of the measurements you need to make however, will be made using the digital readout, The Waveform & Circuit Analyzer’s digital functions give results that are faster, more accurate and subject to much less operator error than conventional analog ‘oscilloscope measurements, Once you have become familiar with the features and operation of the SC3100, you can operate it using the information on the front panel and on the Pull Chart located beneath the unit. The APPLICATION section of this manual includes information on specific applications, elevated, such as when it is located on a shelf above the work area, To relocate the tilt bails simply remove the screw that holds the plastic foot to the case AC Power Connection ‘The SC3100 is wired for use on a 105-125 VAC, 50 or 60 Hz AC line when shipped from the factory. It may be converted for 210-250 VAC operation by the Sencore Service Department. Always connect it to a properly grounded AC outlet. ‘The 3rd wire ground connection ensures continued safety in the event of a circuit failure inside the $C3100, or if the ground of the SC3100 is connected to a test point that has a potentially dangerous voltage. In either case, the ground connection ensures that the metal parts of the 8C3100 do not become a shock hazard, The 3rd wire ground also provides a return path for interference when the unit is used in electrically noisy environments. CAUTION The $C3100 must be used with a properly grounded 3 wire AC system for safe operation and minimum pickup of external interference. eeWARNING Always use an isolation transformer on any piece of equipment that is AC operated and does not have an internal isolation transformer. All warranties are voided if the 3rd wire ground is bypassed, or if damage occurs from making a connection to an unisolated hot-ground system. To operate the SC3100 from an AC lin 1. Connect the power cord to a properly grounded, 105-125 VAC power source. 2. Push the POWER button in to apply power, ‘The button should lock in. 3. After applying power, allow approximately five seconds for the internal circuits to reset ‘The following LEDs should be lit: “CH A&B" CRT Display mode and channel A “DOV”. The DIGITAL READOUT should also show a display. ‘The SC3100 is now fully operational and ready for use. Allow a 20 minute warm up time for specified accuracy. If the LEDs and LCD display do not come on: 1. Confirm that the AC power source is correct. 2. Check the AC line fuse. ‘The traces should be visible on the CRT after the CRT filaments have warmed for approximately 15 seconds. If a trace does not appear use the BEAM FINDER to determine if the trace is positioned out of the CRT display area. See “Locating The Trace With ‘The Beam Finder”, page 14. AC Line Fuse - An AC line fuse is located on the rear panel of the unit, This fuse protects the SC3100 from excessive damage caused by internal failures. If it is blown locate the cause of the problem and correct it before replacing the fuse. Replace the fuse with another of the same type and rating. An incorrect fuse may damage the unit, and will void all ‘warranties. The proper fuse value is 1 amp, type 3AG, 250 volt Slo-Blo. ‘To replace the AC line fuse: 1. Press to release the snap-in fuse holder. 2. Pull the holder and the fuse out of the fuse holder base. AG LINE FUSE Fig. 5 the $3100 fails to come on when power is applied. Check the AC line fuse. 3. Replace the fuse with the correct type and rating. 4, Insert the holder and fuse into the fuse holder base and snap it back into place. CAUTION Using the wrong fuse may damage the SC3100. Only replace the AC line fuse with the following: 1 amp, 3AG, 250 volt Slo-Blo. Simplified CRT Setup ‘The controls on the front panel are grouped according to their function. To display and lock in a waveform on the CRT simply move from right to left across the front panel performing these steps: 1) apply the signal. 2) adjust the trigger controls. 3) adjust the horizontal sweep controls. Follow the above steps whenever you apply a new signal or experience difficulty locking a waveform. ‘The following procedure is a checklist to follow as you learn to use the SC3100. Each step is covered in more detail in later sections. Be sure to read those det to fully understand the effect that each control has on the waveform. After you understand what each control does, use these simplified instructions or the those on the Pull Chart as a reminder. ‘To obtain a waveform display on the CRT: 1. Push the POWER button, 2. Press the desired CRT MODE button to produce a single trace, dual-trace, or vector display.oD 5. Set TIME/OIV {or desired display a aD 4, Set Trigger 3. Apply Signal a. Source to "CH at — «Input coupling bi. Made to "Auto" to"Act 6. Adjust for best display ©: Polarity to "+" 4. Set VOLTS/OW for 4. Adjust LEVEL to —I desired display 2. Select CRT Mode lock trace Fig. 6: Follow his sequence to ge a trace on the SC3100. In this example the irigger controls are set for a channel A signa. 3. Apply the signal to the vertical input: ‘a, Connect the 10X LOW CAPACITY Probe to the INPUT Jack of the desired channel. b, Connect the 10X LOW CAPACITY Probe to the signal. , Set the INPUT COUPLING switch to “AC”. d. Set the VOLTS/DIV switch to “AUTO”, or set it to produce a display that is 4 to 6 CRT graticules high. 4, Adjust the TRIGGER controls to lock the waveform: a. SOURCE to match the input channel, or to the desired reference channel. b. MODE to “Auto”, Use “TV” for composite video signals. ©. POLARITY to the desired polarity. Set to match the syne polarity for composite video, 4. Adjust LEVEL to lock the trace. 5, Adjust the TIMEBASE Control to “AUTO”, or set for the desired number of cycles. 6. Adjust the VERTICAL POSITION, HORIZONTAL POSITION, FOCUS and INTENSITY controls as desired for the best ‘waveform display. More details about the trigger controls may be found 13 in the section entitled "Setting The Trigger Controls, on page 24. Locating The Trace With ‘The Beam Finder [At times you may not be able to see one or both CRT traces because one or more of the CRT controls is improperly set. At these times use the beam finder to help you locate the trace. Pressing the BEAM FINDER button overrides four controls or circuits: 1) ‘The intensity is increased, 2) “AUTO” trigger mode is, selected, 3) The gain of the vertical amplifiers is reduced to bring the trace onto the CRT screen no matter where the VERTICAL POSITION controls are set, and 4) The gain of the horizontal amplifier is reduced. ‘These four conditions will force the trace onto the sereen for any combination of front panel settings. The location of the trace(s) on the CRT when you push the BEAM FINDER button tells you what to do next to obtain a visible trace. Figure 7 shows how to interpret what you see on the CRT when you press the BEAM FINDER button, Note that one or two traces will be displayed depending on which CRT display mode is selected. i‘Adjust: INTENSE ‘Adjust: HORIZONTAL POSITION Fig. 7: The BEAM FINDER button forces a CRT trace by overridding ‘several front panel control setings. CRT Modes The SC3100 has six different CRT display modes which are selected by the four CRT push buttons located below the CRT, as shown in Figure 8, The display options are: 1) Channel A single trace; 2) Channel B single trace; 3) Channel A & B dual chop; 4) Channel A & B dual alternate; 5) Channel A+B add, and 6) X-Y Vector. Each mode is described in the following paragraphs. ‘RT MoD, emO) G4) Gs) GH) Cs) Gay (at) 2 mc roaren a SS Fig. 8 - Use the push buttons located below the CRT display to ‘Select the CAT display mode. Channel A or B Single Trace Signals applied to the channel A and channel B inputs may be displayed independently. Press the CH ‘Aor the CH B button to display the desired signal. A signal applied to one channel will not affect the signal that is displayed on the other channel, Inverting The Channel A Trace ‘The channel A trace may be inverted by pulling the channel A VERTICAL POSITION control out. The inversion affects only the displayed waveform. The triggering polarity of the inverted signal does not change when channel A is inverted. NOTE: Be sure the trace is in the noninverting mode when making standard measurements and setting the triggering controls. Confusion may result if the channel A trace is unintentionally inverted. Dual Trace Press the “A&B” button to view both waveforms simultaneously. The $C3100 automatically selects between dual chop display mode or dual alternate display mode depending on the setting of the TIME/DIV Control. All of the sweep rates between “100 msec” and *.2 msec” produce the dual chop mode. Dual chop means that the CRT electron beam draws portions of each trace as it moves across the CRT. This reduces flicker at the slow sweep speeds. The sweep speeds from “1 jisec” to “.02 j1sec” produce the dual alternate mode. In the dual alternate mode the electron beam draws the complete trace for one channel and then draws the complete trace for the other channel. This prevents the traces from appearing segmented. At times the dual chop mode may cause interference in the trace at the “msec” sweep speeds, as shown in Figure 9. This interference is common with all dual- trace oscilloscopes and is caused by the CRT beam quickly moving between the channel A and B traces. The interference only becomes noticeable when the frequency of the input signal is at or close to a multiple of the chopping frequency. If this interference occurs, place the SC3100 into the dual alternate mode by simultaneously pressing the CH A and CH B CRT MODE buttons so that both LEDs are litFig. 9 - Simultaneously pressing the “CHA” and “CH 8" CRT mode ‘buttons forces the $C3100 into the dual alternate mode to eliminate ‘chop interference a low sweep speeds. Algebraic Addition Or Subtraction (A+B or B-A) ‘Some applications require two signals to be added to form a composite, or subtracted to show the difference of two signals. Press the “A+B ADD" CRT MODE Button to algebraicly add the two signals. To subtract the signals press the “A+B ADD" button and pull the channel A VERTICAL POSITION control out to invert the channel A display. 15 ‘The phase relationship of the signals determines whether the resulting waveform is larger or smaller in amplitude than the applied signals. If the signals are in phase, adding them will increase the size of the displayed waveform and subtracting them will produce a waveform that is either smaller than either of the applied signals or that shows total cancellatitn. If the two signals are 180° out of phase, the opposite occurs: adding produces cancellation and subtracting causes an increase in the resulting waveform. The resulting display of signals having phase shifts other than 0° or 180° will be their instantaneous sum or difference. Vector (X-Y) Operation Press the “X-Y VECTOR” CRT MODE button to use the CRT as an X-Y display. In the vector mode the signal applied to the channel A input causes vertical (¥) deflection and the signal applied to the channel B input causes horizontal (X) deflection. The resulting Lissajous pattern shows the phase and frequency relationships of the two signals, The vertical gain is controlled by the channel A VOLTS/DIV Control, and the channel A VERTICAL POSITION Control adjusts the pattern’s vertical position, Use the channel B VOLTS/DIV Control to set the horizontal gain and use the HORIZONTAL POSITION Control to adjust the horizontal position. (The channel B VERTICAL POSITION Control has no effet when the weetor function is selected).APPLYING SIGNAL TO THE INPUTS. Signals may be supplied to the SC3100 using either of several methods: 1) 10X Low Capacity Probes (supplied); 2) DP270 Direct Probe (optional); 3) PL207 RF Pickup Loop (optional); or 4) 39G157 DCV Probe (optional). Each method offers certain advantages and disadvantages that should be considered before making a connection. With the exception of the PL207 RF Pickup Loop, each of these methods of supplying a signal requires, ‘making a ground connection to the chassis. Connecting To A Hot Chassis ‘As with other oscilloscopes, the BNC input connectors, probe ground leads and front panel GROUND Jack of the SC3100 are connected to the AC line 3rd wire safety ground. This requires extra care when you connect to a “hot chassis” piece of equipment. A hot chassis is a device that does not have an internal isolation transformer. Consequently the chassis ground or common is not referenced at earth ground and is typically 67 volts above earth ground potential. Use With Sweep Generators Or Curve Tracers You can use the vector mode to display the output from a sweep generatot or curve tracer if it provides a horizontal output drive signal. Connect the vertical output of the sweep generator or curve tracer to the CH A INPUT and connect the horizontal output to the CH B INPUT of the SC3100. Use either AC or DC coupling as required. Always connect a hot chassis to an isolation transformer, such as the Sencore PR57 AC “POWERITE"® before connecting the SC3100 to the device. The isolation transformer allows the hot chassis to float in reference to earth ground. Connecting the ground of the SC3100 to the hot chassis without isolating the chassis will damage the chassis power supply or the ground connections in the C3100. Only connect the chassis to the isolation transformer; do not connect the SC3100 to the isolation transformer. NOTE: 1) Using an external transformer with a device that contains internal isolation will not cause a problem. If in doubt, always use an isolation transformer. 2) It may not always be practical to connect some devices to an external isolation transformer because they draw too much AC current or use 3 phase power. Refer to the section “Making Differential Measurements” on page 53 for information on testing these devices. 16 WARNING Always use an isolation transformer on any piece of equipment that is AC operated and does not have an internal isolation transformer. All warranties are voided if the 3rd wire ground is bypassed, or if damage occurs from making a connection to an unisolated hot-ground system. 10X Low Capacity Probes Most measurements are made using the supplied 39G292 10X Low Capacity Probes. These probes isolate the capacitance of the test lead and the input circuits from the circuit test point. This reduces circuit loading and the resulting measurement errors. ‘The special design of the 39G292 Probe protects the 8C3100 to 2000 volts DC or AC peak-to-peak, The 396292 Probe also provides a separate isolated cireuit for making DC voltage measurements independent of the CRT input controls. Fig. 10 Use the supplied 10X probes for most signal connections. ‘The only disadvantage of using the 10X Low Capacity Probe is reduced sensitivity. The 10X Probe limits the lowest measuring range of the SC3100 to 20 mV/div. This allows useful measurement of signals as small as 10 millivolts (.010 volts) which is adequate for most circuit tests, NOTE: Use the DP270 direct probe to increase the input sensitivity to 2 mV {div.Read the digital tests direct and use the markings around the VOLTS/DIV Control directly when using the 10X Probes with the $C3100. You do not need to multiply readings by ten as you do with some other oscilloscopes. (You will need to divide the VOLTS/DIV. seale markings by ten when using a direct, 1X probe.) Special Design Of The 39G292 10X Probe ‘The 39G292 10X Low Capacity Probe is specially designed to route the DC voltage to digital cireuits separately from the CRT or digital peak-to-peak function. You do not need to have the INPUT COUPLING switch set to “DC” to measure DC voltage on the digital display ‘These separate paths require two connections to the 8C3100, The BNC connector couples the signal to the CRT and digital VPP circuits while the mini-banana DCV jack couples the DC voltage to the digital display. Be sure to make both probe connections to the SC3100. Fig. 11 - The mini-banana plug must be connected tothe DCV Jack to,read DC volts using the 10X Low Capacity Probe. ‘The probe contains separate 10:1 dividers for the DC digital display measurement path and for the CRT/VPP measurement path. This prevents loading problems caused by the capacitance of the DC lead, ‘The input impedance of the CRT circuits at the BNC input jack without the probe connected is 1 megohm DC coupled and 2 megohms AC coupled. The impedance at the DCV input jack is 1.5 megohms. Connecting the 10X Probe to the inputs increases both input impedance values by ten, making the AC impedance 10 megohms and the DC input impedance 15 megohms, The circuit test point, however, sees both of these measuring paths in parallel, which effectively make the impedance at the probe tip 6 megohms. While this is a somewhat lower impedance than most oscilloscopes, very few circuits will be affected by the 6 megohm impedance. If circuit loading is a problem, disconnect the DCV lead from the DCV Input Jack to increase the input impedance to 10 megohms stray capactt To apacity crt = ‘Stray capacity m * ‘ oc DCVIN oe 4.5M0 Fig. 12 - Isolation resistors for the AC and DC signals prevent the stray lead capacitance from loading high frequency circuits. Probe ID Bands ‘The supplied 10X Probe Accessory Kit contains two yellow and two red Probe ID Bands. Place one band around the probe wire near the tip and the other band of the same color around the wire near the BNC end. Color coding each probe in this manner allows you to quickly know which probe is connected to each input without tracing the wires back to the probe tip. The two 89G292 10X Low Capacity Probes supplied with your SC3100 may be used on either channel. However, the probe compensation adjustment uniquely matches the probe to the impedance of CH A. or CH B INPUT. Be sure to check the probe ‘compensation and readjust it if you move a probe to the other channel than it was compensated for. Ground Conneetors Each probe should always be grounded to the circuit, ground point to prevent interference or other ‘waveform distortion. The supplied 39G331 10X Probe Accessory Kit contains a 5” and a 12” ground lead for each probe. Always use the short, 5” ground lead when working in high frequency circuits or digital circuits that have square wave signals with fast rise times. The extra inductance of the 12” ground lead will cause distortion in these signals. The 12” ground lead should only be used with low frequency signals, such as video and audio. Connect the alligator clip of either probe to a ground point that is as close as possible to the test point you are measuring. :NOTE: Use the front panel GROUND Jack only for DC voltage measurements or to tie the SC3100 together with other test instruments to a common ground. Do not use it instead of a probe ground lead. WARNING Do not connect the ground leads to a hot chassis unless an isolation transformer is used. Be sure to only connect the probe ground leads to ground points that are the same, earth ground potenti Ground Bayonet Clip - Use the Ground Bayonet clip, included in the optional Probe Accessory Kit, when making tests in digital stages. This clip provides the shortest possible ground length to prevent signal distortion on fast rise time signals, Simply remove the retractable probe tip and slide the Ground Bayonet clip over the probe end, ee Fig. 13 - The (optional) Ground Bayonet provides the shortest ‘possible ground connection and a convenient way to connect fo IC pins. Is prt ofthe optional Probe Accessory Kt. Connecting The Probe To The Circui ‘The supplied 10X Probes may be connected to the circuit in either of two ways; with the retractable * hook tip, or with a needle point connector. To use the retractable tip simply pull back on the collar to expose the hook. Then slip the hook over the ‘component lead or test point and release the collar. ‘The sleeve will slide forward to hold the probe in place. To expose the needle point tip unscrew and remove the retractable tip. The optional Probe Accessory Kit, includes several other options for connecting the probe. 18 Fig. 14 - Pull back on the retractable tp to expose a metal hook to connect tothe circu (a). Unscrew the probe tip to expase a needle ‘robe tp (b). Ground Ring Insulator - Unserewing the retractable probe tip also exposes a metal ground ring. This ground ring allows you to use the optional Ground Bayonet Clip when working in high frequency cireuits, but it may accidently short agains components and IC pins if you are using the needle tip. The supplied Probe Accessory Kit includes an Ground Insulator Ring that slips over the probe tip and covers up the metal ground band on the probe tip, when you use the needle tip. Fig. 15 - Use the supplied Ground insulator Ring to insulate the ‘ground ring when you are not using the retractable probe tp.Probe Frequency Compensation Because 10X probes form an AC voltage divider with the scope input, the impedance of the probe must be set to match the impedance of the oscilloscope input. The 10X Lo Capacity Probes supplied with the 8C3100 have a small trimmer capacitor built into the BNC connector body. In order to obtain a flat frequency response this compensation capacitor must be adjusted to match the probe capacitance to the capacitance at the input jack. ‘Once you have compensated the probe, check the compensation periodically to ensure the probes are still properly matched to the $C3100 input. An uncompensated probe may result in waveform distortion or incorrect amplitude readings. The ‘compensation affects both the CRT display and the digital peak-to-peak function. If you move a probe to the other channel than it was compensated for you ‘may need to readjust the probe compensation, Fig. 16 - The probe compensation capacitor matches the probe ‘capacity tothe scope’s input capacity. NOTE: The DP270 Direct Probe does not contain a compensation capacitor. ‘To check the probe compensation, connect the probe to the PROBE COMP Jack located on the front of the C3100. The resulting CRT display should show a square wave having a flat top and bottom, and square ‘corners, as shown in Figure 17. Adjust the trimmer capacitor if the waveform shows any overshoot or rounding, 17 - Adjust probe compensation so that the signal from the PROBE COMP Jack is square (a). Overshoot (b) or rounding (c) Indicates thatthe probe compensation capacitor needs adjustment. NOTE: The PROBE COMP signal has square edges but may not be 50% duty eyele. Do not use the PROBE COMP signal as a frequency or amplitude calibration ‘To compensate the probes: 1, Connect the probes to the PROBE COMP Jack. 2. Set the VOLTS/DIV Control for both channels to” 8. Set the TIME/DIV Control to *.1 msec”. 4, Lock in the waveform with the TRIGGER controls. 5, Select the channel A display. 6. Adjust the probe compensation capacitor in the probe connection to the CH A INPUT for the best square wave. 7. Repeat stops 5 and 6 for the channel B probe. NOTE: Recompensate the probe if you move it to the input channel other than the one it was compensated