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1. 2120B Only POWER Pushbutton Turns oscillo scope on and off INTENSITY Control Adjusts brightness of trace TRACE ROTATION Control Adjusts to maintain trace at a horizontal position FOCUS Control Adjusts trace focus 2125A Only COMPonent TEST Pushbutton With pushbutton set to in position Component Test mode is enabled Normal scope operation is enabled with pushbutton in out position 2125A Only COMPonent TEST Jack Banana type Hl side input jack for connection to component in Component Test operating mode GND Terminal Oscilloscope chassis ground jack and earth ground via three wire ac power cord On Model 2125A also serves as LO side Component Test jack 10 11 Model 2125A Controls and Indicators CAL Terminal Terminal provides 2 V p p 1 kHz nominal square wave signal This signal is useful for checking probe compensation adjustment as well as providing a rough check of vertical calibration 2125A Only BEAM FIND Pushbutton Momentary contact pushbutton speeds setup of trace positioning by bringing the beam into graticule area operates independently of other display controls VERTICAL CONTROLS 12 VERTical MODE Switch Selects vertical display mode Four position lever switch with the following positions CHI Displays the channel 1 signal by itself CH2 X Y CH2 displays the channel 2 signal by itself X Y used in conjunction with the X Y control and2. NOTE On the Model 2125A you can use the BEAM FINDER pushbutton to locate a trace that has been moved off the screen by the POSition controls When the button is pushed a compressed version of the trace is brought into view which indicates the location of the trace SINGLE TRACE DISPLAY Either channel or channel 2 may be used for single trace operation To observe a waveform on channel 1 1 Perform the steps of the Initial Starting Procedure 2 Connect the probe to the CH 1 X input jack 3 Connect the probe ground clip to the chassis or com mon of the equipment under test Connect the probe tip to the point of measurement 4 Move the CH1 AC GND DC switch out of the GND position to either DC or AC 5 If no waveforms appear increase the sensitivity by turning the CH 1 VOLTS DIV control clockwise to a position that gives 2 to 6 divisions vertical deflection 6 Position the waveform vertically as desired using the CH1 POSition control 7 The display on the CRT may be unsynchronized Refer to the Triggering paragraphs in this section for pro cedures on setting triggering and sweep time controls to obtain a stable display showing the desired number of waveforms DUAL TRACE DISPLAY In observing simultaneous waveforms on channel 1 and 2 the waveforms are usually related in frequency or one of the waveforms is synchronized to the other although the basic frequencies are different To observe two such rela
3. Trigger SOURCE switch to enable X Y display mode DUAL Displays the channel and channel 2 signals simul taneously Dual trace mode may be either alternate or chopped sweep see the description under HOLDOFF PULL CHOP control CONTROLS AND INDICATORS 13 14 15 Fig 2 Model 2120B Controls and Indicators ADD The inputs from channel 1 and channel 2 are summed and displayed as a single signal If the Channel 2 v POSition PULL INVert control is pulled out the input from channel 2 is subtracted from channel 1 and the difference is displayed as a single signal CH1 AC GND DC Switch Three position lever switch with the following positions AC Channel 1 input signal is capacitively coupled dc component is blocked GND Opens signal path and grounds input to vertical amplifier This provides a zero volt base line the position of which can be used as a reference when performing dc measurements DC Direct coupling of channel 1 input signal both ac and dc components of signal produce vertical de flection CHI X Input Jack Vertical input for channel 1 X axis input for X Y operation CH1 X VOLTS DIV Control Vertical attenuator for channel 1 Provides step adjustment of vertical sensitivity When channel 1 VARiable control is set to CAL vertical sensitivity is calibrated in 10 steps from 5 mV div to 5 V div in a 1 2 5 sequence When 16 17 18 the X Y mode of operation is selected this con
4. except for the sections on Delayed Sweep Operation and Component Test which apply only to the Model 2125A Other differences are noted when nec essary SAFETY PRECAUTIONS The following precautions must be ob served to help prevent electric shock When the oscilloscope is used to make measurements in equipment that contains high voltage there is al ways acertain amount of danger from electrical shock The person using the oscilloscope in such conditions should be a qualified electronics technician or other wise trained and qualified to work in such circum stances Observe the TEST INSTRUMENT SAFETY recommendations listed on the inside front cover of this manual Do not operate this oscilloscope with the case removed unless you are a qualified service technician High voltage up to 2100 volts is present when the unit is operating with the case removed The ground wire of the 3 wire ac power plug places the chassis and housing of the oscilloscope at earth ground Use only a 3 wire outlet and do not attempt to defeat the ground wire connection or float the oscil loscope to do so may pose a great safety hazard Special precautions are required to measure or observe line voltage waveforms with any oscilloscope Use the following procedure a Do not connect the ground clip of the probe to either side of the line The clip is already at earth ground and touching it to the hot side of the line may weld or disi
5. of this manual 4 Terminate the output of a signal generator into its characteristic impedance to minimize ringing espe cially if the signal has fast edges such as square waves or pulses For example the typical 50 output of a square wave generator should be terminated into an external 50 Q terminating load and connected to the oscilloscope with 50 Q coaxial cable 5 Probe compensation adjustment matches the probe to the input of the scope For best results compensation should be adjusted initially then the same probe al ways used with the same channel Probe compensation should be readjusted when a probe from a different oscilloscope is used INITIAL STARTING PROCEDURE Until you familiarize yourself with the use of all controls the settings given here can be used as a reference point to obtain a trace on the CRT in preparation for waveform observation 1 Set these controls as follows On both models VERTical MODE to CH1 CH1 AC GND DC to GND Trigger COUPLING to AUTO Trigger SOURCE to CH1 All POSition controls and INTENSITY control cen tered pointers facing up Main Time Base control to 1 mS div On the Model 2125A Sweep Mode switch to MAIN 2 Press the red POWER pushbutton Model 2120B or rotate the POWER control clockwise away from OFF Model 2125A 3 A trace should appear on the CRT Adjust the trace brightness with the INTENSITY control and the trace sharpness with the FOCUS control
6. ALT CHI Causes the channel 1 input signal to become the sweep trigger regardless of the VERTical MODE switch setting X Y Used with two other switches to enable the X Y mode see the Operating Instructions under XY Operation ALT Used with the channel 1 POSition PULL ALTernate TRIGger control to enable alternate triggering Alternate triggering used in dual trace mode permits each waveform viewed to become its own trigger source CH2 The channel 2 signal becomes the sweep trigger regardless of the VERTical MODE switch setting LINE Signal derived from input line voltage 50 60 Hz becomes trigger EXT Signal from EXTernal TRIGger jack becomes sweep trigger Trigger COUPLING Switch Selects trigger cou pling Four position lever switch with the following positions AUTO Selects automatic triggering mode In this mode the oscilloscope generates sweep free runs in absence of an adequate trigger it automatically reverts to triggered sweep operation when an adequate trigger signal is present On the Model 2125A automatic triggering is applicable to both the main sweep and delayed sweep 10 NORM Selects normal triggered sweep operation A sweep is generated only when an adequate trigger signal is present TV V Used for triggering from television vertical sync pulses Also serves as lo pass dc high frequency reject trigger coupling TV H Used for triggering from television horizontal sync pulses
7. Also serves as hi pass low frequency reject trigger coupling 33 TRIGger LEVEL PULL SLOPE Control TRIGger LEVEL Trigger level adjustment determines the point on the triggering waveform where the sweep is trig gered Rotation in the direction counterclock wise selects more negative triggering point rotation in the direction clockwise selects more positive triggering point PULL SLOPE Two position push pull switch The in position selects a positive going slope and the out position selects a negative going slope as triggering point for main sweep 34 EXTernal TRIGger Jack External trigger input for single and dual trace operation REAR PANEL CONTROLS not shown 35 Fuse Holder Line Voltage Selector Contains fuse and selects line voltage 36 Power Cord Receptacle 37 2125A Only CH 2 Y SIGNAL OUTPUT Jack Output terminal where sample of channel 2 signal is available Amplitude of output is nominally 50 mV per division of vertical deflection seen on CRT when terminated into 50 Q Output impedance is 50 Q 38 2125A Only Z Axis Input Jack Input jack for inten sity modulation of CRT electron beam TTL compat ible 5 V p p sensitivity Positive levels increase intensity 39 Handle Tilt Stand 40 Feet Cord Wrap OPERATING INSTRUCTIONS NOTE EQUIPMENT PROTECTION PRECAUTIONS All operating instructions in this chapter apply equally to both Models 2125A and 2120B
8. Five trigger source selections including CH 1 CH 2 alternate EXT and LINE Video Sync Frame TV V or Line TV H triggering selectable for observing composite video waveforms TV H position can also be used as low frequency reject and TV V position can be used as high frequency reject Variable Holdoff Trigger inhibit period after end of sweep adjustable Permits stable observation of complex pulse trains OTHER FEATURES X Y Operation Channel 1 can be applied as horizontal deflection X axis while channel 2 provides vertical deflection Y axis Built in Probe Adjust Square Wave A 2 V p p kHz square wave generator permits probe compensation adjustment Component Test Function Model 2125A Built in X Y type component tester applies fixed level ac signal to components for display of signature on CRT Channel 2 Y Output Model 2125A A buffered 50Q output of the channel 2 signal is available at the rear panel for driving a frequency counter or other instruments The output is 50 mV div nominal into 50Q Z Axis Input Model 2125A Rear panel Z Axis input allows intensity modulation Supplied With Two Probes SPECIFICATIONS CRT Type 6 inch rectangular with integral graticule P31 phosphor Display Area 8 x 10 div 1 div 1 cm Accelerating Voltage 2 kV Phosphor P31 Trace Rotation Electrical front panel adjustable Scale Illumination Continuously variable Model 2125A Beam Finder
9. However this setting is not suitable for phase or timing comparison measurements For such measurements both traces must be triggered by the same sync signal Alternate triggering can only be used in dual trace mode VERT MODE set to DUAL and with alter nate sweep only PULL CHOP not engaged 3 In the LINE position triggering is derived from the input line voltage 50 60 Hz and the trigger SOURCE switch is disabled This is useful for meas urements that are related to line frequency 4 In the EXT position the signal applied to the EXT TRIG jack becomes the trigger source This signal must have a timing relationship to the displayed wave forms for a synchronized display TRIG LEVEL PULL SLOPE Control Refer to Fig 3 A sweep trigger is developed when the trigger source signal crosses a preset threshold level Rotation of the TRIG LEVEL control varies the threshold level In the direction clockwise the triggering threshold shifts to a more posi tive value and in the direction counterclockwise the triggering threshold shifts to a more negative value When Slope Range Slope Range Fig 3 Function of Slope and Level Controls the control is centered the threshold level is set at the approximate average of the signal used as the triggering source Proper adjustment of this control usually synchro nizes the display The TRIG LEVEL control adjusts the start of the sweep to almost an
10. Test Voltage 6 V rms maximum open Test Current 11 mA maximum shorted Test Frequency Line frequency 60 Hz in USA OTHER SPECIFICATIONS Cal Probe Compensation Voltage 2 V p p 3 square wave 1 kHz nominal CH 2 Y Output Model 2125A Output Voltage 50 mV div nominal into 50 ohm load Output Impedance Approximately 50 ohms Frequency Response 20 Hz to 30 MHz 3 dB Intensity Modulation Model 2125A Input Signal TTL level intensity increasing with more positive levels decreased intensity with more negative levels Input Impedance Approximately 50 kO Usable Frequency Range DC to 5 MHz Maximum Input Voltage 30 V dc ac peak Power Requirements 100 130 VAC or 200 260 VAC 50 60 Hz 38 watts Dimensions H X W x D 5 2 X 12 8 X 15 7 132 X 324 x 398 mm Weight 16 8 lbs 7 6 kg Environment Within Specified Accuracy 10 to 4 35 C 10 80 relative humidity Full Operation 0 to 50 C 10 80 relative humidity Storage 30 to 70 C 10 90 relative humidity ACCESORIES SUPPLIED Two Switchable X1 X10 Probes Instruction Manual AC Line Cord i 2 CONTROLS AND INDICATORS Fig 1 GENERAL FUNCTION CONTROLS ON Indicator Lights when oscilloscope is on 2125A Only POWER Scale ILLUMination Con trol Clockwise rotation from OFF position turns os cilloscope on Further clockwise rotation increases amount of graticule illumination
11. semiconductors insert the diode s or transistor s leads only two at a time into the COMP TEST and GND jacks make sure that the leads touch the metal walls inside the jacks To test in circuit or to test IC s or devices with leads too short to insert into the COMP TESTand GND jacks a pair of test leads can be used to connect the COMP TEST and GND jacks to the component s Combinations of Components Using the component test feature it is also possible to observe the signatures of combinations of components Combinations cause signatures that are a combination of the individual signatures for each component For example a signature for a resistor and capacitor in parallel will produce a signature with the ellipse of the capacitor but the resistor would cause the ellipse to be at an angle determined by the value of the resistor When testing combinations of compo nents it is important to make sure that all the components being connected are within measurement range In Circuit Testing The component test feature can be very effective in locat ing defective components in circuit especially if a known good piece of equipment is available for reference Com pare the signatures from the equipment under test with signatures from identical points in the reference unit When 19 OPERATING INSTRUCTIONS Silicon Diode Fig 9 Typical P N Junction Signature 10 V Zener Diode Fig 10 Typical Zener Signature s
12. speed cannot be slower than main sweep speed DELAY Only delayed sweep operates while main sweep stays inactive DELAY TIME POSition control determines the starting point of the delayed sweep X Y Used with the VERTical MODE switch and Trig ger SOURCE switch to select X Y operating mode The channel input becomes the X axis and the channel 2 input becomes the Y axis Trigger source and coupling are disabled in this mode 2120B Only X Y Switch Used with the VERTical MODE switch and Trigger SOURCE switch to se lect X Y operating mode The channel 1 input be comes the X axis and the channel 2 input becomes the Y axis Trigger source and coupling are disabled in this mode CONTROLS AND INDICATORS TRIGGERING CONTROLS 30 HOLDOFF PULL CHOP Control 31 32 HOLDOFF Rotation adjusts holdoff time trigger inhibit period beyond sweep duration When control is rotated fully counterclockwise the holdoff period is MIN inum normal The holdoff period increases pro gressively with clockwise rotation PULL CHOP When this switch is pulled out in the dual trace mode the channel 1 and channel 2 sweeps are chopped and displayed simultaneously normally used at slower sweep speeds When it is pushed in the two sweeps are alternately displayed one after the other normally used at higher sweep speeds Trigger SOURCE Switch Selects source of sweep trigger Four position lever switch with the following positions CHI X Y
13. warranty does not apply in the event of misuse or abuse of the product or as a result of unauthorized alterations or repairs It is void if the serial number is altered defaced or removed B K Precision Corp shall not be liable for any consequential damages including without limitation damages resulting from loss of use Some states do not allow limitation of incidental or consequential damages so the above limitation or exclusion may not apply to you This warranty gives you specific rights and you may also have other rights which vary from state to state 24 OSCILLOSCOPE APPLICATIONS INFORMATION paKk PRECISIONS GUIDEBOOK TO sSCILLOSCOPES O One of the best tutorials on oscilloscopes in the industry Valuable to those with little knowledge of oscilloscopes as well as the experienced technician or engineer who wishes to refresh their memory or explore new uses for oscilloscopes CONTAINS e Numerous Application Examples Showing How To Gain The Most From Your Scope s Features And Capabilities e Proper Probe Selection And Use e Oscilloscope Terminology e Typical Scope Controls And Their Usage e Scope Theory Of Operation Download your FREE copy from our Web site www bkprecision com BK PRECISION 1031 Segovia Circle Placentia CA 92870 2000 B K Precision Corp 481 312 9 001 Printed in Taiwan
14. INSTRUCTION 5 aa al N FUE FSPEVEE MODELS 2120B MAN UAL and 2125A 30 MHz DUAL TRACE OSCILLOSCOPES Fe illl a SLL TEST INSTRUMENT SAFETY Normal use of test equipment exposes you to a certain amount of danger from electrical shock because testing must often be performed where exposed high voltage is present An electrical shock causing 10 milliamps of current to pass through the heart will stop most human heartbeats Voltage as low as 35 volts dc or ac rms should be considered dangerous and hazardous since it can produce a lethal current under certain conditions Higher voltage poses an even greater threat because such voltage can more easily produce a lethal current Your normal work habits should include all accepted practices that will prevent contact with exposed high voltage and that will steer current away from your heart in case of accidental contact with a high voltage You will significantly reduce the risk factor if you know and observe the following safety precautions Don t expose high voltage needlessly in the equipment under test Remove housings and covers only when necessary Turn off equipment while making test connections in high voltage circuits Discharge high voltage capacitors after removing power If possible familiarize yourself with the equipment being tested and the location of its high voltage points However remember that high voltage may appear at unexpected points in defe
15. Model 2125A VERTICAL AMPLIFIERS CH 1 and CH 2 Sensitivity 5 mV div to 5 V div 1 mv div to 1 V div at X5 MAG Attenuator 10 calibrated steps in 1 2 5 sequence Vernier control provides fully adjustable sensitivity between steps range 1 1 to at least 1 3 Accuracy 3 5 mV to 5 V div 5 at X5 MAG Input Resistance 1 MO 2 Input Capacitance 25 pF 10 pF Frequency Response 5 mV div to 5 V div DC to 30 MHz 3 dB X5 MAG DC to 10 MHz 3 dB Rise Time 12 nS 35 nS at X5 MAG Overshoot Less than 596 Operating Modes CH 1 CH 1 single trace CH 2 CH 2 single trace DUAL CH 1 and CH 2 dual trace Alternate or Chop selectable at any sweep rate ADD Algebraic sum of CH 1 CH 2 Chop Frequency Approximately 500 kHz Polarity Reversal CH 2 invert Maximum Input Voltage 400 V dc ac peak HORIZONTAL AMPLIFIER Input through channel 1 input X Y mode CH 1 X axis CH 2 Y axis Sensitivity Same as vertical channel 2 Input Impedance Same as vertical channel 2 Frequency Response DC to 1 MHz 3 dB X Y Phase Difference 3 or less at 50 KHz Maximum Input Voltage Same as vertical channel 1 SWEEP SYSTEM Operating Modes Model 2125A Main Mix both main and delayed sweep displayed Delay only delayed sweep displayed X Y Model 2120B Main only Main Time Base 0 1 uS div to 2 0 S div in 1 2 5 sequence 23 steps Vernier control provides fully adjusta
16. ble sweep time between steps Delayed Time Base Model 2125A only 0 1 uS div to 2 0 S div in 1 2 5 sequence 23 steps Accuracy 3 except 6 on 0 2 S div and 20 on 0 1 wS div Sweep Magnification X10 10 Holdoff Continuously adjustable for main time base from NORM to 5 times normal Delay Time Position Control sets percentage of display that is devoted to main and delayed sweep Delay Jitter 1 10 000 of full scale sweep time TRIGGERING Trigger Modes AUTO free run NORM TV V TV H Trigger Source CH 1 CH 2 Alternate EXT LINE Slope or SPECIFICATIONS Trigger Coupling AUTO Sweep free runs in absence of suitable trigger signal NORM Sweep triggered only by adequate trigger signal TV V Video vertical sync pulses are selected Also usable for high frequency reject TV H Video horizontal sync pulses are selected Also usable for low frequency reject Trigger Sensitivity Auto 1 5 div internal 20 5 Vp p external 100 Hz 40 MHz 2125A 100 Hz 30 MHz 2120B Norm 1 5 div internal 20 5 Vp p external 100 Hz 40 MHz 2125A DC 30 MHz 2120B TV V 1 0 div internal 20 5 Vp p external DC 1 kHz 2125A 20 Hz 1 kHz 2120B TV H 1 0 div internal 20 5 Vp p external 1 kHz 100 kHz Maximum External Trigger Voltage 300 V dc ac peak COMPONENT TESTER Model 2125A Components Tested Resistors capacitors inductors and semiconductors
17. ce When the X Y mode of operation is selected this control pro vides step adjustment of Y axis sensitivity CH2 VARiable PULL X5 MAG Control VARiable Rotation provides vernier adjustment of channel 2 vertical sensitivity In the fully clockwise CAL position the vertical attenuator is calibrated Coun terclockwise rotation decreases gain sensitivity In X Y operation this control becomes the vernier Y axis sensitivity control PULL X5 MAG When pulled out increases vertical sensitivity by a factor of five Effectively provides two extra sensi tivity settings 2 mV div and 1 mV div In X Y mode increases Y sensitivity by a factor of five CH2 Y Input Jack Vertical input for channel 2 Y axis input for X Y operation CH2 AC GND DC Switch Three position lever switch with the following positions AC Channel 2 input signal is capacitively coupled dc component is blocked GND Opens signal path and grounds input to vertical amplifier This provides a zero volt base line the position of which can be used as a reference when performing dc measurements DC Direct coupling of channel 2 input signal both ac and dc components of signal produce vertical de flection HORIZONTAL CONTROLS 23 24 Main Time Base TIME DIV Control Provides step selection of sweep rate for the main time base When the VARiable Sweep control is set to CAL sweep rate is calibrated This control has 23 steps from 0 1 wS div to 2 S d
18. ctive equipment Use an insulated floor material or a large insulated floor mat to stand on and an insulated work surface on which to place equipment make certain such surfaces are not damp or wet Use the time proven one hand in the pocket technique while handling an instrument probe Be particularly careful to avoid contacting a nearby metal object that could provide a good ground return path When using a probe touch only the insulated portion Never touch the exposed tip portion When testing ac powered equipment remember that ac line voltage is usually present on some power input circuits such as the on off switch fuses power transformer etc any time the equipment is connected to an ac outlet even if the equipment is turned off Some equipment with a two wire ac power cord including some with polarized power plugs is the hot chassis type This includes most recent television receivers and audio equipment A plastic or wooden cabinet insulates the chassis to protect the customer When the cabinet is removed for servicing a serious shock hazard exists if the chassis is touched Not only does this present a dangerous shock hazard but damage to test instruments or the equipment under test may result from connecting the ground lead of most test instruments including this oscilloscope to a hot chassis To make measurements in hot chassis equipment always connect an isolation transformer between the ac outlet and
19. curate voltage measurements 3 on 10 cali brated ranges from 5 mV div to 5 V div Vertical gain fully adjustable between calibrated ranges SWEEP FEATURES Calibrated Time Measurements Accurate 3 time measurements The main sweep has 23 calibrated ranges from 2 S div to 0 1 uS div The delayed sweep on the Model 2125A has 23 cali brated ranges from 2 S div to 0 1 ui S div Sweep time is fully adjustable between calibrated ranges X10 Sweep Magnification Allows closer examination of waveforms increases maximum sweep rate to 10 nS div DUAL TIME BASE FEATURES Model 2125A Dual Sweep Generators Main sweep gives normal waveform display delayed sweep may be operated at faster sweep speed to expand a portion of the waveform Four Sweep Modes Choice of main sweep only delayed sweep only main sweep and delayed sweep sharing the trace percentage of main delayed sweep adjustable or X Y Adjustable Start Of Delayed Sweep DELAY TIME POSition control allows adjustment of delayed sweep starting point TRIGGERING FEATURES Two Trigger Modes Selectable normal triggered or automatic sweep modes Triggered Sweep Sweep remains at rest unless adequate trigger signal is applied Fully adjustable trigger level and or slope FEATURES AUTO Sweep Selectable AUTO sweep provides sweep without trig ger input automatically reverts to triggered sweep operation when adequate trigger is applied Five Trigger Sources
20. e the closer to horizontal the trace will be Values from 10 to about 5 kQ are within measurement range Values below 10 Q will appear to be a dead short while values above 5 kQ will appear to be an open circuit Fig 6 shows some typical resistance signatures To test a resistor insert one of the resistor s leads into the white COMP TEST jack and the other into the GND jack make sure that the leads touch the metal walls inside the jacks To test in circuit a pair of test leads can be used to connect the COMP TEST and GND jacks to the compo nent s Capacitors CAUTION Be sure to discharge capacitors by short ing the leads together before connecting to the COMP TEST jack Some capaci tors can retain a voltage high enough to damage the instrument A purely capacitive impedance produces a signature that is an ellipse or circle Value is determined by the size and shape of the ellipse A very low capacitance causes the ellipse to flatten out horizontally and become closer to a straight horizontal line and a very high capacitance causes the ellipse to flatten out vertically and become closer to a straight vertical line Values from about 0 33 uF to about 330 uF are within measurable range Values below 0 33 UF will be hard to distinguish from an open circuit and values above 330 uF will be hard to distinguish from a short circuit Fig 7 shows several typical capacitance signatures To test a capacitor insert the capacitor s pos
21. e type of measurement desired An explanation of the various controls which affect synchroni zation is given to help you select the proper setting over a wide range of conditions Trigger COUPLING Switch 1 In the AUTO position automatic sweep operation is selected In automatic sweep operation the sweep generator free runs to generate a sweep without a trigger signal However it automatically switches to triggered sweep operation if an acceptable trigger source signal is present The AUTO position is handy when first setting up the scope to observe a waveform it provides sweep for waveform observation until other controls can be properly set Once the controls are set operation is often switched back to the normal trigger ing mode since it is more sensitive Automatic sweep must be used for dc measurements and signals of such low amplitude that they will not trigger the sweep The NORM position provides normal triggered sweep operation The sweep remains at rest until the selected trigger source signal crosses the threshold level set by the TRIG LEVEL control The trigger causes one sweep to be generated after which the sweep again remains at rest until triggered In the normal triggering mode there will be no trace unless an adequate trigger signal is present In the ALT VERTICAL MODE of dual trace operation with the SOURCE switch also set to ALT there will be no trace unless both channel 1 and channel 2 signals are adequate
22. epair charges contact the factory before shipping the product Return all merchandise to B K Precision Corp with pre paid shipping The flat rate repair charge includes return shipping to locations in North America For overnight shipments and non North America shipping fees contact B K Precision Corp IMPORTANT Include with the instrument your complete return shipping address contact name phone number and description of problem Service Department B K Precision Corp 1031 Segovia Circle Placentia CA 92870 Phone 714 237 9220 Fax 714 237 9214 E mail service bkprecision com 23 LIMITED WARRANTY B K Precision Corp warrants to the original purchaser that its product and the component parts thereof will be free from defects in workmanship and materials for a period of three years from the date of purchase Model 2125A or two years from the date of purchase Model 2120B B K Precision Corp will without charge repair or replace at its option defective product or component parts upon delivery to an authorized B K Precision service contractor or the factory service department accompanied by proof of the purchase date in the form of a sales receipt To obtain warranty coverage in the U S A this product must be registered by completing and mailing the enclosed warranty registration card to B K Precision 1031 Segovia Circle Placentia CA 92870 within fifteen 15 days from the date of purchase Exclusions This
23. for triggering Typically signals that pro duce even one division of vertical deflection are ade quate for normal triggered sweep operation The TV H and TV V positions are primarily for viewing composite video waveforms Horizontal sync pulses are selected as trigger when the trigger COU PLING switch is setto the TV H position and vertical sync pulses are selected as trigger when the trigger COUPLING switch is set to the TV V position The TV H and TV V positions may also be used as low frequency reject and high frequency reject coupling respectively Additional procedures for observing video waveforms are given later in this section of the manual OPERATING INSTRUCTIONS Trigger SOURCE Switch The trigger SOURCE switch CH 1 CH 2 etc selects the signal to be used as the sync trigger 1 If the SOURCE switch is set to CH 1 or CH 2 the channel 1 or channel 2 signal becomes the trigger source regardless of the VERTICAL MODE selec tion CH 1 or CH 2 are often used as the trigger source for phase or timing comparison measurements 2 By setting the SOURCE switch to ALT same as CH1 and PULL ALT TRIG pulled alternating trig gering mode is activated In this mode the trigger source alternates between CH 1 and CH 2 with each sweep This is convenient for checking amplitudes waveshape or waveform period measurements and even permits simultaneous observation of two wave forms which are not related in frequency or period
24. gger is permitted The HOLDOFF control allows this period to be extended by a variable amount if desired A Holdoff not used B Holdoff used Fig 4 Use of HOLDOFF Control This control is usually set to the MIN position fully counterclockwise because no additional holdoff period is necessary The HOLDOFF control is useful when a com plex series of pulses appear periodically such as in Fig 4B Improper sync may produce a double image as in Fig 4A Such a display could be synchronized with the VAR SWEEP control but this is impractical because time meas urements are then uncalibrated An alternate method of synchronizing the display is with the HOLDOFF control The sweep speed remains the same but the triggering of the next sweep is held off for the duration selected by the HOLDOFF control Turn the HOLDOFF control clock wise from the MIN position until the sweep starts at the same point of the waveform each time MAGNIFIED SWEEP OPERATION Since merely shortening the sweep time to magnify a portion of an observed waveform can result in the desired portion disappearing off the screen magnified display should be performed using magnified sweep Using the lt P position control move the desired portion of waveform to the center of the CRT Pull out the PULL X10 knob to magnify the display ten times For this type of display the sweep time is the Main Time Base TIME DIV control setting divided by 10 Rotation of the lt P
25. holder slot located between fuseholder and receptacle Pry fuseholder away from receptacle 3 When reinstalling fuseholder be sure that the fuse is installed so that the correct line voltage is selected see LINE VOLTAGE SELECTION LINE VOLTAGE SELECTION To select the desired line voltage simply insert the fuse and fuse holder so that the appropriate voltage is pointed to by the arrow Be sure to use the proper value fuse see label on rear panel 20 PERIODIC ADJUSTMENTS Probe compensation and trace rotation adjustments should be checked periodically and adjusted if required These procedures are given below Probe Compensation 1 Connect probes to CH 1 and CH 2 input jacks Per form procedure for each probe one probe at a time 2 Set the probe to X10 compensation adjustment is not possible in the X1 position Touch tip of probe to CAL terminal 4 Adjust oscilloscope controls to display 3 or 4 cycles of CAL square wave at 5 or 6 divisions amplitude 5 Adjust compensation trimmer on probe for optimum square wave minimum overshoot rounding off and tilt Refer to Fig 11 Correct Compensation Over Compensation Insufficient Compensation Fig 11 Probe Compensation Adjustment Trace Rotation Adjustment 1 Set oscilloscope controls for a single trace display in CH 1 mode and with the channel 1 AC GND DC switch set to GND 2 Use the channel 1 POSition control t
26. ignatures are identical or very similar the tested component is good When signatures are distinctively different the tested component is probably defective MAINTENANCE The following instructions are for use by qualified service personnel only To avoid electrical shock do not perform any serv icing other than contained in the operat ing instructions unless you are qualified to do so High voltage up to 2000 V is present when covers are removed and the unit is oper ating Remember that high voltage may be retained indefinitely on high voltage capacitors Also remember that ac line voltage is present on line voltage input circuits any time the instrument is plugged into an ac outlet even if turned off Unplug the oscilloscope and dis charge high voltage capacitors before performing service procedures FUSE REPLACEMENT If the fuse blows the ON indicator will not light and the oscilloscope will not operate The fuse should not normally open unless a problem has developed in the unit Try to determine and correct the cause of the blown fuse then replace only with the correct value fuse For 110 125 V line voltage operation use an 800 mA 250 V fuse For 220 240 V line voltage operation use a600 mA 250 V fuse The fuse is located on the rear panel adjacent to the power cord receptacle Remove the fuseholder assembly as follows 1 Unplug the power cord from rear of scope 2 Insert a small screwdriver in fuse
27. itive lead into the white COMP TEST jack and the negative lead into the GND jack make sure that the leads touch the metal walls inside the jacks To test in circuit or to test a capacitor with leads that are too short to fitinto the COMP TEST and GND jacks a pair of test leads can be used to connect the COMP TEST and GND jacks to the component s OPERATING INSTRUCTIONS Short Circuit 10 Resistor 200 Resistor 5 1 kQ Resistor Fig 6 Typical Resistive Signatures 17 OPERATING INSTRUCTIONS 4 7 uF Capadtor 300 uF Capacitor Fig 7 Typical Capacitive Signatures 18 Inductors Like capacitance a purely inductive impedance produces a signature that is an ellipse or circle and value is determined by the size and shape of the ellipse A very high inductance causes the ellipse to flatten out horizontally and a very low inductance causes the ellipse to flatten out vertically Values from about 0 05 H to about 5 H are within measurement range Values below 0 05 H will be hard to distinguish from a short circuit and values above 5 H will be hard to distin guish from an open Fig 8 shows several ty
28. iv in a 1 2 5 sequence 2125A Only DELAY Time Base TIME DIV Con trol Provides step selection of sweep rate for delayed 25 26 27 28 29 CONTROLS AND INDICATORS sweep time base This control has 23 steps from 0 1 uS div to 2 S div in a 1 2 5 sequence 2125A Only DELAY TIME POSition Control Sets starting point of delayed sweep Clockwise rotation causes delayed sweep to begin earlier VARiable Sweep Control Rotation of control is ver nier adjustment for sweep rate In fully clockwise CAL position sweep rate is calibrated On the Model 2125A this control is the vernier adjustment for both the main and delayed time bases lt P poSition PULL X10 MAG Control lt gt position Horizontal X position control PULL X10 MAG Selects ten times sweep magnification when pulled out normal when pushed in Increases maximum sweep rate to 10 nS div 2125A Only Sweep Mode Switch Selects sweep horizontal mode Four position rotary switch with the following positions MAIN Only the main sweep operates with the delayed sweep inactive MIX The main and delayed sweep share a single trace main sweep occupies the left portion of the display delayed sweep occupies the right portion of the display The DELAY TIME POSition control de termines the percentage of display that is main sweep and the percentage of display that is delayed sweep main sweep is usually brighter than the delayed sweep Delayed sweep
29. ly the DELAY Time Base from being set to a slower sweep speed than the MAIN Time Base For example if the MAIN Time Base is set to 0 1 ms div the slowest possible DELAY Time Base sweep speed is also 0 1 ms div even if the control is set slower COMPONENT TEST OPERATION Model 2125A CAUTION Do not apply an external voltage to the COMP TEST jacks Only non powered circuits should be tested with this unit Testing powered circuits could damage the instrument and increase the risk of electrical shock The component test function produces a component sig nature on the CRT by applying an ac signal across the device and measuring the resulting ac current The display represents a graph of voltage X versus current Y The 16 component test function can be used to view the signatures of resistors capacitors inductors diodes and other semi conductor devices Devices may be analyzed in circuit or out of circuit and combinations of two or more devices may be displayed simultaneously Each component produces a different signature and the components can be analyzed as outlined below Component Test mode is activated by depressing the COMPonent TEST switch The SWEEP MODE switch must not be in the DELAY position Resistors A purely resistive impedance produces a signature that is a straight line A short circuit produces a vertical line and an open circuit causes a horizontal line Therefore the higher the resistanc
30. ments out of warranty APPENDIX IMPORTANT CONSIDERATIONS FOR RISE TIME AND FALL TIME MEASUREMENTS Error in Observed Measurement The observed rise time or fall time as seen on the CRT is actually the cascaded rise time of the pulse being meas ured and the oscilloscope s own risetime The two rise times are combined in square law addition as follows Tobserved Tue y T scope y The effect of the oscilloscope s rise time is almost negli gible when its rise time is at least 3 times as fast as that of the pulse being measured Thus slower rise times may be measured directly from the CRT However for faster rise time pulses an error is introduced that increases progres sively as the pulse rise time approaches that of the oscillo Scope Accurate measurements can still be obtained by calculation as described below Direct Measurements The Models 2125A and 2120B oscilloscopes have a rated rise time of 12 ns Thus pulse rise times of about 36ns or greater can be measured directly Most fast rise times are measured at the fastest sweep speed and using X10 magni fication For the Models 2125A and 2120B this sweep rate is 10 ns div A rise time of less than about four divisions at this sweep speed should be calculated 22 Calculated Measurements For observed rise times of less than 36 ns the pulse rise time should be caluclated to eliminate the error introduced by the cascaded oscilloscope rise time Calculate
31. ng ps ulis reb RPRER o gt 12 Initial Starting Procedure 0 12 Single Trace Display 0004 12 Dual Trace Display 00 02 20 e eee ee 12 WIG PCTING sob oe ihe eh Soba M eR bas 13 Magnified Sweep Operation 15 Page OPERATING INSTRUCTIONS Continued X Y Operation cos tiee pai e ee ee aes 15 Video Signal Observation 000005 15 Application Guidebook 0200 000 15 Delayed Sweep Operation 005 15 Component Test Operation 0 16 MAINTENANCE 00 00 e cece eee 20 Fuse Replacement oos cscssi i bombe emm 20 Line Voltage Selection 00005 20 Periodic Adjustments l l eese 20 Calibration CHECK 32 v2 oda 34 ex Le ote ewe 21 Instrument Repair Service sse usus 21 APPENDIX i422 RES br TI PY 22 Important Considerations for Rise Time and Fall Time Measurements 22 Service Information 2 2 cese e ees 23 Limited Warranty 0 0 ppu e cee eee ee eee 24 Guidebook To Oscilloscopes Availability 20000 inside back cover FEATURES LOW COST HIGH PERFORMANCE B K Precision s entry level oscilloscopes Models 2120B and 2125A are economically priced to equal the competi tion but offer higher performance than the competition For example most competitor s entry level oscilloscopes have a 20 MHz bandwidth while B K Preci
32. ntegrate the probe tip and cause possible injury plus possible damage to the scope or probe b Insert the probe tip into one side of the line voltage receptacle then the other One side of the recepta cle should be hot and produce the waveform The other side of the receptacle is the ac return and no waveform should result 11 CAUTION The following precautions will help avoid damage to the oscilloscope Never allow a small spot of high brilliance to remain stationary on the screen for more than a few seconds The screen may become permanently burned A spot will occur when the scope is set up for X Y operation and no signal is applied Either reduce the intensity so the spot is barely visible apply signal or switch back to normal sweep operation It is also advisable to use low intensity with AUTO triggering and no signal applied for long periods A high intensity trace at the same position could cause a line to become perma nently burned onto the screen Do not obstruct the ventilating holes in the case as this will increase the scope s internal temperature Excessive voltage applied to the input jacks may dam age the oscilloscope The maximum ratings of the inputs are as follows CH 1 and CH 2 400 V dc ac peak EXT TRIG 300 V dc ac peak Z AXIS INPUT Model 2125A 30 V dc and ac peak Always connect a cable from the ground terminal of the oscilloscope to the chassis of the equipment under te
33. o position the trace over the center horizontal line on the graticule scale The trace should be exactly parallel with the horizontal line 3 Usethe TRACE ROTATION adjustment on the front panel to eliminate any trace tilt CALIBRATION CHECK A general check of calibration accuracy may be made by displaying the output of the CAL terminal on the screen This terminal provides a square wave of 2 V p p This signal should produce a displayed waveform amplitude of four divisions at 5 V div sensitivity for both channel 1 and 2 with probes set for direct With probes set for X10 there should be four divisions amplitude at 50 mV div sensitivity The VARIABLE controls must be set to CAL during this check NOTE The CAL signal should be used only as a general check of calibration accuracy not as a signal source for performing recali bration adjustments a voltage standard calibrated at several steps and of 0 3 or better accuracy is required for calibration adjustments The CAL signal should not be used as a time base standard 21 MAINTENANCE INSTRUMENT REPAIR SERVICE Because of the specialized skills and test equipment re quired for instrument repair and calibration many custom ers prefer to rely upon B K Precision for this service To use this service even if the oscilloscope is no longer under warranty follow the instructions given in the SERVICE INFORMATION portion of this manual There is a flat rate charge for instru
34. on permits selection of horizontal or vertical sync pulses for sweep triggering when viewing composite video waveforms When the TV H mode is selected horizontal sync pulses are selected as triggers to permit viewing of horizontal lines of video A sweep time of about 10 us div is appropriate for displaying lines of video The VAR SWEEP control can be set to display the exact number of waveforms desired When the TV V mode is selected vertical sync pulses are selected as triggers to permit viewing of vertical fields and frames of video A sweep time of 2 ms div is appropriate for viewing fields of video and 5 ms div for complete frames two interlaced fields of video At most points of measurement a composite video signal is of the polarity that is the sync pulses are negative and the video is positive In this case use SLOPE If the waveform is taken at a circuit point where the video wave form is inverted the sync pulses are positive and the video is negative In this case use SLOPE APPLICATIONS GUIDEBOOK B K Precision offers a Guidebook to Oscilloscopes which describes numerous applications for this instrument and important considerations about probes It includes a glossary of oscilloscope terminology and an understanding of how oscilloscopes operate It may be downloaded free of charge from our Web site www bkprecision com DELAYED SWEEP OPERATION Model 2125A Refer to Fig 5 Delayed sweep opera
35. pical inductance signatures To test an inductor insert one of the inductor s leads into the white COMP TEST jack and the other into the GND jack make sure that the leads touch the metal walls inside the jacks To test in circuit or to test an inductor with leads that are too short to be inserted into the COMP TEST and GND jacks a pair of test leads can be used to connect the COMP TEST and GND jacks to the component s 1 Henry Inductor 5 Henry Inductor Fig 8 Typical Inductive Signatures Semiconductors Purely semiconductor devices such as diodes and transis tors will produce signatures with straight lines and bends Typical diode junctions produce a single bend with a hori zontal and vertical line as shown in Fig 9 Zener diodes produce a double bend with two vertical and one horizontal line as shown in Fig 10 value is determined by the distance of the leftmost vertical component from the center gradu ation on the CRT The maximum Zener voltage observable on this feature is about 15 V It is also possible to test transistors and IC s by testing one pair of pins at a time NOTE When testing diodes it is important to connect the diode s cathode to the white COMP TEST jack and the anode to the GND jack Reversing the polarity will not damage the device but the horizontal and vertical components of the signature will appear in different quadrants of the display To test
36. position control can then be used to select the desired portion of the waveforms X Y OPERATION X Y operation permits the oscilloscope to perform many measurements not possible with conventional sweep opera tion The CRT display becomes an electronic graph of two instantaneous voltages The display may be a direct com parison of the two voltages such as stereoscope display of stereo signal outputs However the X Y mode can be used to graph almost any dynamic characteristic if a transducer is used to change the characteristic frequency temperature velocity etc into a voltage One common application is fre quency response measurements where the Y axis corresponds to signal amplitude and the X axis corresponds to frequency 1 On the Model 2125A set the SWEEP MODE switch to the X Y position On the Model 2120B depress the X Y switch On both models set the Trigger Source and VERTical MODE switches to X Y 2 In this mode channel becomes the X axis input and channel 2 becomes the Y axis input The X and Y positions are now adjusted using the lt gt position and the channel 2 Y POSition controls respectively 3 Adjust the amount of vertical Y axis deflection with the CH 2 VOLTS DIV and VARIABLE controls 4 Adjust the amount of horizontal X axis deflection with the CH 1 VOLTS DIV and VARIABLE con trols 15 OPERATING INSTRUCTIONS VIDEO SIGNAL OBSERVATION Setting the COUPLING switch to the TV H or TV V positi
37. pulse rise time as follows 2 2 Tpulse PLNS E Cie Limits of Measurement Measurements of pulse rise times that are faster than the scope s rated rise time are not recommended because a very small reading error introduces significant error into the calculation This limit is reached when the observed rise time is about 1 3 times greater than the scope s rated rise time about 16 ns minimum for the Models 2125A and 2120B Probe Considerations For fast rise time measurements which approach the limits of measurement direct connection via 50 Q coaxial cable and 50 Q termination is recommended where possible When a probe is used its rise time is also cascaded in square law addition Thus the probe rating should be considerably faster than the oscilloscope if it is to be disregarded in the measurement SERVICE INFORMATION Warranty Service Please return the product in the original packaging with dated proof of purchase to the address below Clearly state in writing the performance problem and return any leads connectors and accessories that you are using with the device Non Warranty Service Return the product in the original packaging to the address below Clearly state in writing the performance problem and return any leads connectors and accessories that you are using with the device Customers not on open account must include payment in the form of a money order or credit card For the most current flat rate r
38. sion s Models 2120B and 2125A offer a 30 MHz bandwidth These oscilloscopes are built by and backed by B K Precision a company that has been selling reliable durable value priced test instru ments for over 50 years CRT FEATURES Rectangular CRT Rectangular CRT with large 8 x 10 centimeter viewing area On Model 2125A graticule is equipped with variable scale illumination Convenience Trace rotation electrically adjustable from front panel 0 10 90 and 100 markers for rise time meas urements DUAL TRACE FEATURES Dual Trace Models 2120B and 2125A each have two vertical input channels for displaying two waveforms simultane ously Selectable single trace either CH 1 or CH 2 or dual trace Alternate or chop sweep selectable at all sweep rates Sum and Difference Capability Permits algebraic addition or subtraction of channel 1 and channel 2 waveforms displayed as a single trace Useful for differential voltage and distortion measure ments HIGH FREQUENCY FEATURES Wide Bandwidth Conservatively rated 3 dB bandwidth is dc to 30 MHz Fast Rise Time Rise time is less than 12 ns Fast Sweep Maximum sweep speed of 10 ns div with X10 MAG assures high frequencies and short duration pulses are displayed with high resolution VERTICAL FEATURES High Sensitivity 5 mV div sensitivity for full bandwidth High sen sitivity 1 mV div and 2 mV div using PULL X5 gain control Calibrated Voltage Measurements Ac
39. st Without this precaution the entire current for the equipment under test may be drawn through the probe clip leads under certain circumstances Such condi tions could also pose a safety hazard which the ground cable will prevent The probe ground clips are at oscilloscope and earth ground and should be connected only to the earth ground or isolated common of the equipment under test To measure with respect to any point other than the common use CH 2 CH 1 subtract operation ADD mode and INV 1 with the channel 2 probe to the point of measurement and the channel 1 probe to the point of reference Use this method even if the reference point is a dc voltage with no signal OPERATING INSTRUCTIONS OPERATING TIPS The following recommendations will help obtain the best performance from the oscilloscope 1 Always use the probe ground clips for best results attached to a circuit ground point near the point of measurement Do not rely solely on an external ground wire in lieu of the probe ground clips as undesired signals may be introduced 2 Avoid the following operating conditions a Direct sunlight b High temperature and humidity c Mechanical vibration d Electrical noise and strong magnetic fields such as near large motors power supplies transformers etc 3 Occasionally check trace rotation probe compensa tion and calibration accuracy of the oscilloscope using the procedures found in the MAINTENANCE section
40. sweep and may become visible in the displayed waveform However you may select chop sweep at any sweep time for special applications Adjust the channel 1 and 2 POSition controls to place the channel 1 trace above the channel 2 trace Set the CH 1 and CH 2 VOLTS DIV controls to a position that gives 2 to 3 divisions of vertical deflec tion for each trace If the display on the screen is unsynchronized refer to the Triggering paragraphs in this section of the manual for procedures for setting triggering and sweep time controls to obtain a stable display showing the desired number of waveforms When the VERTical MODE switch is set to ADD the algebraic sum of CH 1 CH 2 is displayed as a single trace When the PULL INV switch is pulled out the algebraic difference of CH 1 CH 2 is displayed If two waveforms have no phase or frequency relation ship there is seldom reason to observe both wave forms simultaneously However these oscilloscopes do permit the simultaneous viewing of two such unre lated waveforms using alternate triggering Refer to the paragraphs on Triggering Trigger SOURCE Switch for details on alternate triggering 13 OPERATING INSTRUCTIONS TRIGGERING The Models 2125A and 2120B Oscilloscopes provide versatility in sync triggering for ability to obtain a stable jitter free display in single trace or dual trace operation The proper settings depend upon the type of waveforms being observed and th
41. ted waveforms simultaneously perform the following Connect probes to both the CH 1 X and CH 2 Y input jacks 2 Connect the ground clips of the probes to the chassis or common of the equipment under test Connect the tips of the probes to the two points in the circuit where waveforms are to be measured To view both waveforms simultaneously set the VERTical MODE switch to DUAL and select either ALT alternate or CHOP with the PULL CHOP switch In the ALT sweep mode PULL CHOP switch pushed in one sweep displays the channel signal and the next sweep displays the channel 2 signal in an alternating sequence Alternate sweep is normally used for viewing high frequency or high speed wave forms at sweep times of 1 ms div and faster but may be selected at any sweep time In the CHOP sweep mode PULL CHOP switch pulled out the sweep is chopped switched between channel 1 and channel 2 Using CHOP one channel does not have to wait for a complete swept display of the other channel Therefore portions of both chan nel s waveforms are displayed with the phase relation ship between the two waveforms unaltered Chop sweep is normally used for low frequency or low speed waveforms at sweep times of 1 ms div and slower or where the phase relationship between chan nel 1 and channel 2 requires measurement If chop sweep is used at sweep times of 0 2 ms div and faster the chop rate becomes a significant portion of the
42. the equipment under test The B K Precision Model TR 110 or 1604A Isolation Transformer or Model 1653A or 1655A AC Power Supply is suitable for most applications To be on the safe side treat all two wire ac powered equipment as hot chassis unless you are sure it has an isolated chassis or an earth ground chassis Never work alone Someone should be nearby to render aid if necessary Training in CPR cardio pulmonary resuscitation first aid is highly recommended Instruction Manual for BK PRECISION Models 2120B and 2125A 30 MHz Dual Trace Oscilloscopes 2000 B K Precision Corp This symbol on oscilloscope means refer to instruction manual for further precautionary information This symbol appears in the manual where the corresponding information is given BK PRECISION 1031 Segovia Circle Placentia CA 92870 TABLE OF CONTENTS Page TEST INSTRUMENT SAFETY inside front cover FEATURES en e tenner Seen ee 3 SPECIFICATIONS e505 2003 he embed eee eb 5 CONTROLS AND INDICATORS 7 General Function Controls 0 7 Vertical Controls o c 00s0 ee este nen RR 7 Horizontal Controls 0 000000008 9 Triggering Controls 0 0 0 0005 9 Rear Panel Controls cers 50053 44eeers sans Sees 10 OPERATING INSTRUCTIONS 0 11 Safety Precautions 00 00000 11 Equipment Protection Precautions 11 Operati
43. tion is achieved by use of both the main sweep and the delayed sweep and allows any portion of a waveform to be magnified for observation Unlike X10 magnification delayed sweep allows selectable steps of magnification 1 Set the Sweep Mode switch to the MAIN position and adjust the oscilloscope for a normal display 2 Set the Sweep Mode switch to the MIX position The display will show the main sweep on the left portion representing the MAIN Time Base control setting and the delayed sweep on the right portion repre senting the DELAY Time Base control setting The MAIN Time Base portion of the trace usually will be brighter than the delayed time base portion Fig 5 shows a typical display for the MIX display mode 3 Shift the percentage of the display that is occupied by the main sweep by adjusting the DELAY TIME POSition control Counterclockwise rotation causes more of the display to be occupied by the main sweep OPERATING INSTRUCTIONS Delayed Sweep Fig 5 MIX SWEEP MODE Display and clockwise rotation causes more of the display to be occupied by the delayed sweep 4 Set the Sweep Mode switch to the DELAY position to display only the magnified delayed sweep portion of the display NOTE In order to obtain meaningful results with delayed sweep the DELAY Time Base control must set be set to a faster sweep speed than the MAIN Time Base control Because of this the oscilloscope automat ically prevents electrical
44. trol provides step adjustment of X axis sensitivity CH1 VARiable PULL X5 MAG Control VARiable Rotation provides vernier adjustment of channel 1 vertical sensitivity In the fully clockwise CAL position the vertical attenuator is calibrated Coun terclockwise rotation decreases gain sensitivity In X Y operation this control becomes the vernier X axis sensitivity control PULL X5 MAG When pulled out increases vertical sensitivity by a factor of five Effectively provides two extra sensi tivity setings 2 mV div and 1 mV div In X Y mode increases X sensitivity by a factor of five CH1 POSition PULL ALT TRIGger Control POSition Adjusts vertical position of channel 1 trace PULL ALT Used in conjunction with the Trigger SOURCE switch to activate alternate triggering See the de scription under the Trigger SOURCE switch CH2 V POSition PULL INVert Control POSition Adjusts vertical position of channel 2 trace In X Y operation rotation adjusts vertical position of X Y display 19 20 21 22 PULL INVert When pushed in the polarity of the channel 2 signal is normal When pulled out the polarity of the channel 2 signal is reversed thus inverting the waveform CH2 VOLTS DIV Control Vertical attenuator for channel 2 Provides step adjustment of vertical sensi tivity When channel 2 VARiable control is set to CAL vertical sensitivity is calibrated in 10 steps from 5 mV div to 5 V div in a 1 2 5 sequen
45. y desired point on a waveform On sine wave signals the phase at which sweep begins is variable Note that if the TRIG LEVEL control is rotated toward its extreme or setting no sweep will be developed in the normal trigger mode because the triggering threshold ex ceeds the peak amplitude of the sync signal When the PULL SLOPE control is set to the in position the sweep is developed from the trigger source waveform as it crosses a threshold level in a positive going direction When the PULL SLOPE control is set to the out position a sweep trigger is developed from the trigger source waveform as it crosses the threshold level in a negative going direction MAIN TIME BASE Control Set the Main Time Base TIME DIV control to display the desired number of cycles of the waveform If there are too many cycles displayed for good resolution switch to a faster sweep time If only a line is displayed try a slower sweep time When the sweep time is faster than the wave form being observed only part of it will be displayed which may appear as a straight line for a square wave or pulse waveform HOLDOFF Control Refer to Fig 4 A holdoff period occurs immediately after the comple tion of each sweep and is a period during which triggering of the next sweep is inhibited The normal holdoff period varies with sweep rate but is adequate to assure complete retrace and stabilization before the next sweep tri
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