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The Oscilloscope Training Package

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A BriefIntroduction OperatingPrinciples Controls &Indicators BasicOperatingInstructions Applicationsof theOscilloscope

Glossary

Copyright &COPY; 1997-8 Jigar C Shah

The Oscilloscope

A Brief Introduction…

What’s Inside?

As you can see in the diagram above, an analog scope has two major signalpaths. The first is the vertical signal path, which ultimately is responsiblefor deflecting the CRT beam vertically in response to the input signal. Thesecond path is the horizontal. It triggers the scope and moves the beam fromleft to right across the screen. In a typical display, time is representedhorizontally and voltage is represented by the vertical axis.

The Vertical Channels

When a signal comes into an analog scope, the first thing it sees are theattenuators. Attenuators match the high impedance of the scope probes

(typically 1 M or 10 M ) to the low impedance of the vertical preamplifiers.The attenuators also scale the input signals to a level the vertical preampscan handle. The amount of attenuation and preamp gain is set by the frontpanel vertical sensitivity knob.

Triggering

The triggering portion plays a very important part in the operation of ascope-it determines where (in time) the trace starts. In essence, thetriggering circuits tell the horizontal section when to start moving the beamfrom the left side of the CRT to the right. If the trace starts too early, thepart of interest on the signal won't be seen. The same is true if it starts toolate. The figure below gives you an idea of what happens.

How does the trigger circuit know when to trigger? It gets a replica of thesignal, called the sync pickoff, from the selected trigger source. This syncpickoff is compared to a pre-set trigger voltage that is set with the front

panel trigger level knob. Most analog scopes let you specify a slope as wellas a trigger voltage. This allows you to trigger at a specific point on a risingor falling transition.

When the trigger circuit finds a voltage and transition from the source thatmatches those set with the trigger controls, it tells the horizontal sweepcircuits to start moving the beam from left to right. The speed of the beamis determined by the seconds/division knob on the front panel. As the beamis moved horizontally across the screen, the vertical amplifiers move thebeam up and down, relative to the input voltage.

Both the horizontal sweep and vertical deflection information have to arriveat the CRT at the same time. If they don't, the scope won't be able to displaythe voltage information properly.

Look at the block diagram at the top of this section. Since the delays in thehorizontal path are longer, vertical information will reach the CRT beforethe horizontal information. The solution to the problem is to put a calibrateddelay into the vertical path so both horizontal and vertical signals will get tothe CRT at the same time. When properly adjusted, an analog scope doesnot display the signal fluctuations before the trigger event.

The Horizontal Section

For external triggering, the horizontal path of an analog scope has anattenuator like the vertical channels. This attenuator serves the samepurpose as those in the vertical channels, i.e., impedance matching andscaling the external trigger signal. However, the horizontal attenuator isfollowed by trigger comparison circuits, instead of a preamp, as in thevertical channels.

The horizontal portion of the scope, which is responsible for moving thetrace along the time or horizontal axis, directly affects the time accuracy ofan analog scope. The horizontal beam movement is controlled by a voltageramp (called the sweep ramp); the time interval accuracy of the scopedepends heavily on this ramp.

Once the trigger comparator has found a valid trigger, it tells the horizontalsweep ramp generator to start. As the ramp rises, it causes the beam tomove from left to right across the CRT. Since the left to right movementrepresents time on the CRT, the ramp must be very linear. If the ramp hasnon-linearities, the beam moves at different rates across the screen.Typically, ramp linearity controls time interval accuracy of an analog scopewithin ±3%.

The CRT

The last major portion of an analog scope is the display or CRT. AnalogCRTs are vector displays that can move the beam to any point directly. Asignal from the vertical amplifier moves the beam in the vertical direction.This may seem obvious, but it brings up a very important point. The CRTand its drivers must be able to deflect the beam vertically as fast as thesignal rises. What this means is that the CRT bandwidth must be the sameas the input bandwidth of the scope! High bandwidth CRTs pose several

problems. As CRT bandwidth goes up, the following happens:

Cost of the CRT goes up;●

Accuracy of the CRT goes down;●

Reliability of the CRT goes down.●

To keep the cost of the CRT down while keeping the accuracy andreliability up, the scope must use as low a bandwidth CRT as possible.However, since the CRT must have the same bandwidth as the scope, highbandwidth analog scopes demand high bandwidth CRTs. The only realsolution is to move to a new architecture.

Summary

In this first section we have talked about how an analog scope works. Wealso pointed out some of the shortcomings of current analog scopearchitecture. Here are some of the key points to remember about analogscopes:

There are two major signal paths-horizontal and vertical;●

Everything (including the CRT) must work at the same speed as theinput signal;

●

All input channels are usually multiplexed through a single verticalpath to the CRT;

●

The horizontal path is responsible for triggering;●

The scope triggers on a voltage level and rising or falling slope;●

As input bandwidth goes up, cost of the CRT also goes up, whilereliability and accuracy of the CRT go down.

●

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Oscilloscope Training Package Programmed by Jigar C. Shah NTU FinalYear Project.


The Oscilloscope

Operating Principles : The Cathode Ray Tube

The Cathode Ray Tube Many logic analysers and some DSOs usemagnetically deflected c.r.t.s either as monochrome or colour. This is thetype of display technology used in TV sets.

In the c.r.t. storage oscilloscope, the cathode ray tube is basically similar tothe electrostatistically deflected type of tube described below; but with theaddition of one or more storage meshes.

The cathode ray tube is the main component of an oscilloscope. A cathoderay tube consists basically of an electrode assembly mounted in anevacuated glass vessel. The electrodes perform the following functions:

A triode assembly generates the electron beam, originally called the'cathode ray'. It consists of a cathode K heated by a filament F, acontrol grid G and the first beam-acceleration electrode (1).

●

An electrode (2) focuses the beam.●

The beam is then further accelerated before reaching the deflectionplates.

●

The vertical deflection plates change the direction of the beam inproportion to the potential difference between them. When this is zero,i.e. the two plates are at the same potential, the beam passes throughundeflected. The vertical deflection plates are so called because theycan deflect the bean in the vertical direction, so that it hits the screen ata higher or lower point; they are actually mounted horizontally aboveand below the beam. Similarly the horizontal deflection plates permitthe beam to be deflected to left or to right.

●

The deflected beam then hits the fluorescent coating on the innersurface of the glass screen of the c.r.t. The coating consists of t thinlayer of phosphor, a preparation of very fine crystals of metallic saltsdeposited on the glass. The 'spot' or point of impact of the beam glows,emitting light in all directions including forwards. Modern c.r.t.s arealuminized, i.e. a think layer of aluminum is evaporated on to the rearof the coated screen. The electrons pass through this with littleretardation., causing the phosphor to glow as before, but not the lightemitted rearwards is reflected forwards, almost doubling the usefullight output.

●

The potential at the focus electrode is adjusted to obtain a very small roundspot on the end of the tube. Unfortunately, if no other control were

provided, it would often be found that the focus control setting forminimum spot width was different from that for minimum spot height. Thisis avoided by providing an astigmatism control. In the case of a simplecathode ray tube this consists of a potentiometer that adjusts the voltage onthe final anode and screen relative to the deflection plate voltages. Alternateadjustments of the focus and astigmatism controls then permit the smallestpossible spot size to be achieved. With more complicated tubes using a highpost deflection acceleration ratio another electrode is often needed. This is a'geometry' electrode and is connected to another preset potentiometer,which is adjusted for minimum 'pincushion' or 'barrel' distortion of thedisplay. When an electron beam passes between two horizontal plates thathave a potential difference of V volts between them it is deflected verticallyby an amount:

where

L = Length of the plates

D = distance between the plates and the point on the axis where thedeflection is measured

d = distance between the plates

Va = acceleration voltage applied to the beams at the level of the plates

K = a constant relating the charge of an electron to its mass

Brilliance or intensity modulation (also called Z modulation) is obtained bythe action of a potential applied to the cathode or grid hat controls theintensity of the beam. Generally, a change of 5V will produce a noticeablechange of brightness, while a swing of about 50V will extinguish amaximum intensity trace. The beam is normally extinguished during'flyback' or retrace; by means of an auxiliary 'blanking' electrode, which candeflect the beam so that it no longer passes through the deflection plates

and hence does not reach the screen.

TUBE SENSITIVITY

The deflection plates of a c.r.t. are connected to amplifiers, which can berelatively simple design when the required output amplitude is low; it istherefore desirable for the tube sensitivity to be as high as possible. Toenable the amplifier to have a wide bandwidth, the capacity between theplates must be kept low, so they must be small and well seperated. On theother handm in order to obtain a suitably clear trace of a signal with lowrepitition frequency (or single shot) the energy of the beam must be high.But the ideal tube must be:

Short (not cumbersome) : D small

Bright (high acceleration voltage) : Va large

And with low acceleration deflection-plate capacity: L small, d large.

This gives the tubes with very low sensitivity, considering the formulae:

The requirements for high sensitivity contradicts the terms of the equation.Practical cathode ray tubes are therefore the result of a compromise.However, techniques have been developed to improve a selected parameterwithout prejudice to the others.

Post deflection acceleration (p.d.a) is one of these; To improve the tracebrightness while retaining good sensitivity, it is arranged that the beampasses through the deflection system in a low energy condition; post

deflection acceleration is then applied to the electrons. This is achieved byapplying a voltage of several kilovolts to the screen of c.r.t.

Spiral p.d.a is a development of the basic p.d.a technique, and consists ofthe application of the p.d.a. voltage to a resistive spiral (500M Ohms)deposited on the inner tube surface between the screen and the deflectionsystem. The unformity of the electric field is improved, which reducesdistortion. In addition to the effect of the p.d.a. field between the deflectionplates is weaker, so the loss in sensitivity caused by this field is reduced.

The use of a field grid, avoids any reduction in sensitivity caused by theeffect of the post deflection acceleration field. A screen is interposedbetween the deflection system and the p.d.a; this makes the tube sensitivityindependent of the p.d.a, a significant benefit. The screen must, of course,be transparent to the electrons and is formed from a very fine metallic grid.With this system we reach the domain of modern cathode ray tubes.

The next development is the electrostatic expansion lens. By modifying theshape of the field gird it is possible to create, with respect to the otherelectrodes, an electric field that acts on the beam in the same way as a lensacts on a light beam. It is therefore possible to increase the beam deflectionangle, for example by a factor of 2 which improves the sensitivity by thesame amount.

The field can also be formed by quadripolar lenses.

For example, if the sensitivity of a spiral tube is 30 V/cm in the X-axis and10 V/cm in the Y axis, then the sensitivity of a lens fitted tube, for the sametrace brightness, may be 8V/cm in X and 2V/cm in Y or even better.

To improve the sensitivity by modifying the deflection system it isnecessary to do one of two things:

Reduce the distance between the plates, increasing the capacity betweenthem; in addition it must be possible to deflect the beam without it strikingthem.

Lengthen the plates, again increasing the capacity, however, the transit timeinvolved limits the application of this idea.

The transmit time is the time taken for an electron to pass through thedeflection system

BACK TO MAIN MENUOscilloscope Training Package Programmed by Jigar C. Shah NTU Final

Year Project.Copyright &COPY; 1997-8 Jigar C Shah

The Oscilloscope

First Looks : Controls & Indicators

Please click on the various parts of the Oscilloscope for adescription of the part.

1. CH1 Position Control

Rotation of this knob will adjust the vertical position of the Channel 1 waveform on thescreen. In the X-Y operation, rotation adjusts vertical position of display.

Back to Oscilloscope Diagram

2. CH1 Volts/Div Control & Variable Control

For the Volts/Div Control, it is a vertical attenuator for channel 1. Provides step adjustmentof verticaal sensitivity in 1-2-5 sequence. VARIABLE control is turned to the CALposition, the calibrated vertical sensitivity is obtained. In X-Y operation, this control servesas the attenuator for Y-axis.

Rotation of the variable control provides fine control of channel 1 vertical sensitivity. Inthe fully clockwise (CAL) position, the vertical attenuator is calibrated. In X-Y operation,this control serves as the Y-axis attenuation fine adjustment.


3. CH1 AC-GND-DC Switch

This switch is the Channel 1 vertical axis coupling mode selector, for X-Y operation, theY-Axis coupling mode control.

AC: AC Input coupling with blocking of any DC signalcomponent.

GND: Vertical amplifier is disconnected from the input signaland connected to ground. This mode is useful indetermining the zero reference.

DC: DC Coupling, with both the DC and AC components ofthe input signal displayed on the CRT.


4. CH1 INPUT Jack

Vertical input for channel 1 trace in normal sweep operation. Y-axis input for X-Yoperation.


5. CH2 Position / PULL INVert Control

CH2 Position:Rotation adjusts vertical position of channel 2 trace.

INV:Push-pull swtich selects channel 2 signal inverted when pulled out.


6. CH2 Volts/Div Control & Variable Control

Volts/Div Knob:For the Volts/Div Control, it is a vertical attenuator for channel 1. Provides step adjustmentof verticaal sensitivity in 1-2-5 sequence. VARIABLE control is turned to the CALposition, the calibrated vertical sensitivity is obtained. In X-Y operation, this control servesas the attenuator for X-axis.

Variable Control:Rotation of the variable control provides fine control of channel 1 vertical sensitivity. Inthe fully clockwise (CAL) position, the vertical attenuator is calibrated. In X-Y operation,this control serves as the X-axis attenuation fine adjustment.


7. CH2 AC-GND-DC Switch

Three position lever switch which operates as follows :

AC: Blocks DC Component of channel 2 input signal.

GND:

Opens singnal path and grounds input to vertical amplifier.This provides a zero-signal base line, the position of whichcan be used as a reference when performing DCmeasurements.

DC: Direct input of AC and DC component of channel 2 inputsignal.


8. CH2 INPUT Jack

Vertical input for channel 2 trace in normal sweep operation. X-axis input in X-Yoperation.


9. MODE Switch

Selects the basic operating mode of the oscilloscope.

CH1:Only the input signal to channel 1 is displayed as a single trace.

CH2:

Only the input signal to channel 2 is displayed as a single trace.

ALT:Alternate sweep is selected regardless of sweep time.

CHOP:Chop sweep is selected regardless of sweep time at approximately 300 KHz.

ADD:

The waveforms from channel 1 and channel 2 inputs are added and the sum is displayed asa single trace. When the CH2 INV Button is engaged, the waveform from channel 2 issubtracted from the channel 1 waveform and the difference is displayed as a single trace.


10. GND Terminal

Earth and chassis ground reference.


11. CAL Terminal

Provides 1 kHz, 1 V peak-to-peak square wave signal. This is useful for probecompensation adjustment.


12. EXT Trigger Input Jack

Input terminal for external sync signal.When SOURCE switch is selected in EXT position, the input signal at the EXT TRIGinput jack becomes the trigger.


13. Power Switch

A press of this switch turns the power ON.


14. Power Indicator

Lights when the POWER swtich is pressed.


15. Intensity (REAL) Control

Controller for adjusting the brightnesss of the real-time waveform.


16. Focus / PULL Astig Control

FOCUS: Focus adjustment

ASTIG: Used to bring the waveform into the best condition with the FOCUS adjustmentby adjusting trace and spot aberration. Pull the knob to make a spot circular.


17. Scale Illum / PULL Trace Rota Control

SCALE ILLUM:Brightness adjustment of the scale of the CRT. For photographing, rotate the knob to adjustbright to prevent halation caused by too bright illumination.

TRACE ROTA:Tilt adjustment of the horizontal bright line in the case where goemagnetism influences the

bright line to tilt.


18. Variable SWEEP TIME/DIV Control

A SWEEP Time / Div Control

Range select dial of 19 ranges from 0.2us/div to 0.5s/div.To calibrate the set value, rotate the SWEEP VARIABLE controlle clockwise up to theCAL position.

B SWEEP Time / Div Control

Range select dial of 17 ranges from 50ms/div to 0.2us/div. Set this dial to a value same asthe A SWEEP Time/Div Control or higher than it.

A SWEEP Variable Control

Fine sweep time adjustment. In the fully clockwise (CAL) position, the sweep time iscalibrated.


19. Horizontal Position / PULL 10X Magnification Control

Horizontal position controller, which provides horizontalal shift of waveform. By pullingthe knob, the sweep time is quickened ten times.In the X-Y operation, rotation adjusts horizontal posistion of display.


20. Level / PULL Slope (-) Control

LEVEL:Trigger level adjustment determines point on triggering waveform where A sweeptriggered.


21. Hold Off Control

HOLD OFF:Adjusts holdoff (trigger inhibit period beyond sweep duration). Clockwise rotation fromthe NORM position increases holdoff time, up to 10 times at the MAX position (fullyclockwise).

Trace Seperation Control

Adjusts vertical seperation between A sweep and B sweep (control has effect only in theALT of HORIZ. MODE).

Clockwise rotation increases seperation; B sweep moves down with respect to A sweep upto 4 divisions.


22. Coupling Switch

Selects coupling for sync trigger signal.

AC:Trigger is AC coupled. Blocks DC component of input signal; mostly commonly usedposition.

HFrej:Sync signal is DC coupled through a low-pass filter to eliminate high frequencycomponents for stable triggering of low frequency signals.

DC:The sync signal is DC coupled for sync which includes the effect of DC components.

TV FRAME:Vertical sync pulses of a composite video signal are selectec for triggering.

TV LINE:Horizontal sync pulses of a composite video signal are selected for triggering.


23. Source Switch

Sweep trigger source select switch.

VERT MODE:The sweep trigger source is selected with the MODE selector for the vertical operation.When the vertical MODE selectoris set to CH1, the channel-1 signal is used as a triggersource. When is is ser to CH2, the channel 2 signal is used as a trigger source. When ser toALT both the channel 1 and channel 2 signals are used alternatively. When set to CHOP orADD, the channel 1 signal is used as a trigger source.

CH1:Channel 1 signal is used as a trigger source.

CH2:Channel 2 signal is used as a trigger source.

LINE:Sweep is triggered by line voltage.


24. Triggering Mode Control

Selects triggering mode.

AUTO:Triggered sweep operation when trigger signal is present, automatically generates sweep inabsence of trigger signal.

NORM:Normal triggered sweep operation. No trace is presented when a proper trigger signal is notapplied.

X-Y:X-Y operation. Channel 1 input signal produces vertical deflection (Y-axis). Channel 2input signal produces horizontal deflection (X-axis).This operates regardless vertical MODE selection.

SINGLE:Single sweep mode

RESET:Reset mode of single sweep operation. when reset, the switch returns to the SINGLEposition, with the READY LED lighting until completion of the sweep.


Ready Indicator

When the reset is single-sweep operation, this lamp lights and remains lit until the sweepoperation is completed.


Horizontal Mode Switch

Used to select the horizontal display mode.

A:Only A sweep is operative, with the B sweep dormant.

ALT:A sweep alternates with the B sweep. For this mode of operation, the B sweep appears asan intensified section of the A sweep.

B:Only delayed B sweep is operative.

X-Y:Channel 1 becomes the Y-axis and channel 2 becomes the X-axis for the X-Y operation.The setting of the vertical MODE and TRIG MODE switches have no effect.


Delay Time Postion Control

Used to set delay time of the B sweep start point from the A sweep start point, if theHORIZ MODE selector is set to ALT or B position. (Delay time position) It controls delaytime continuously between 0,2 and 10 times of a set value with the A sweep time/divcontroller.


CRT Screen

This is where all the output signals will be displayed.


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The Oscilloscope

Getting Started : Basic Operating Instructions

OPERATION AS A GENERAL-USE OSCILLOSCOPE

The 5 basic operations of the scope

NORMAL SWEEP DISPLAY OPERATION

MAGNIFIED SWEEP OPERATION

ALTERNATE SWEEP OPERATION

X-Y OPERATION

SINGLE SWEEP OPERATION



The Oscilloscope

Put it to Work : Applications of the Scope

The Oscilloscope KENWOOD TMI's CS -5135

PROBE COMPENSATION

For an accurate measurement, perform appropriate probe correction prior to measurement.

1. Connect a probe to the INPUT terminal, and set each switch so that normal sweep isdisplayed.

2. Connect the probe to the CAL terminal on the front panel, and adjust the SWEEPTIME/DIV switch so that several cycles of this signal are displayed.

3. Adjust compensation trimmer on probe for optimum square wave waveshape (minimumovershoot, rounding offm and tilt).

TRACE ROTATION COMPENSATION

Rotation from a horizontal trace position can be the cause of measurement errors.

Adjust the controls for a single display. Set the AC-GND-DC switch to GND and TRIGMODE to AUTO. Adjust the CH1 position control such that the trace is over the centrehorizontal graticule line. If the trace appears to be rotated from horizontal, align it with thecentre graticule line using the TRACE ROTATION control located on the front panel.

Please click on the topics below to learn that application :

1. DC VOLTAGE MEASUREMENT

2. MEASUREMENT OF THE VOLTAGE BETWEEN TWO POINTS ON THEWAVEFORM

3. ELIMINATION OF UNDESIRED SIGNAL COMPONENTS

4. TIME MEASUREMENTS

5. TIME DIFFERENCE MEASUREMENTS

6. PULSE WIDTH MEASUREMENTS

7. PULSE RISETIME AND FALLTIME MEASUREMENTS

8. PHASE DIFFERENCE MEASUREMENTS

9. FREQUENCY MEASUREMENTS

10. RELATIVE MEASUREMENTS

11. SWEEP MULTIPLICATION (MAGNIFICATION)

12. APPLICATION OF X-Y OPERATION



The Oscilloscope

A - Z : Glossary of terms

AC

(Alternating Current) A signal in which the current and voltage vary ina repeating pattern over time.

ADC

(Analog-to-Digital Converter) A digital electronic component thatconverts an electrical signal into discrete binary values.

Alternate Mode

A display mode of operation in which the oscilloscope completestracing one channel before beginning to trace another channel.

Amplitude

The magnitude of a quantity or strength of a signal. In electronics,amplitude usually refers to either voltage or power.

Attenuation

A decrease in signal voltage during its transmission from one point toanother.

Averaging

A processing technique used by digital oscilloscopes to eliminate noisein a signal.

Bandwidth

A frequency range.

CRT

(Cathode-Ray Tube) An electron-beam tube in which the beam can befocused on a luminescent screen and varied in both position andintensity to produce a visible pattern. A television picture tube is aCRT.

Chop Mode

A display mode of operation in which small parts of each channel aretraced so that more than one waveform can appear on the screensimultaneously.

Circuit Loading

The unintentional interaction of the probe and oscilloscope with thecircuit being tested, distorting the signal.

Compensation

A probe adjustment for 10X probes that balances the capacitance ofthe probe with the capacitance of the oscilloscope.

Coupling

The method of connecting two circuits together. Circuits connectedwith a wire are directly coupled; circuits connected through a capacitoror a transformer are indirectly (or AC) coupled.

Cursor

An on-screen marker that you can align with a waveform to takeaccurate measurements.

DC (Direct Current)

A signal with a constant voltage and current.

Division

Measurement markings on the CRT graticule of the oscilloscope.

Earth Ground

A conductor that will dissipate large electrical currents into the Earth.

Envelope

The outline of a signal's highest and lowest points acquired over manyrepetitions.

Equivalent-time Sampling

A sampling mode in which the oscilloscope constructs a picture of arepetitive signal by capturing a little bit of information from eachrepetition.

Focus

The oscilloscope control that adjusts the CRT electron beams tocontrol the sharpness of the display.

Frequency

The number of times a signal repeats in one second, measured in Hertz(cycles per second). The frequency equals 1/period.

Gigahertz (GHz)

1,000,000,000 Hertz; a unit of frequency.

Glitch

An intermittent error in a circuit.

Graticule

The grid lines on a screen for measuring oscilloscope traces.

Ground

A conducting connection by which an electric circuit or equipment isconnected to the earth to establish and maintain a reference voltagelevel.

1.

The voltage reference point in a circuit.2.

Hertz (Hz)

One cycle per second; the unit of frequency.

Kilohertz (kHz)

1000 Hertz; a unit of frequency.

Interpolation

A "connect-the-dots" processing technique to estimate what a fastwaveform looks like based on only a few sampled points.

Megahertz (MHz)

1,000,000 Hertz; a unit of frequency.

Megasamples per second (MS/s)

A sample rate unit equal to one million samples per second.

Microsecond

A unit of time equivalent to 0.000001 seconds.

Millisecond (ms)


Nanosecond (ns)


Noise

An unwanted voltage or current in an electrical circuit.

Oscilloscope

An instrument used to make voltage changes visible over time. Theword oscilloscope comes from "oscillate," since oscilloscopes areoften used to measure oscillating voltages.

Peak - V[p]

The maximum voltage level measured from a zero reference point.

Peak-to-peak - V[p-p]

The voltage measured from the maximum point of a signal to itsminimum point, usually twice the V[p] level.

Peak Detection

An acquisition mode for digital oscilloscopes that lets you see theextremes of a signal.

Period

The amount of time it takes a wave to complete one cycle. The periodequals 1/frequency.

Phase

The amount of time that passes from the beginning of a cycle to thebeginning of the next cycle, measured in degrees.

Probe

An oscilloscope input device, usually having a pointed metal tip formaking electrical contact with a circuit element and a flexible cable fortransmitting the signal to the oscilloscope.

Pulse

A common waveform shape that has a fast rising edge, a width, and afast falling edge.

RMS

Root mean square.

Real-time Sampling

A sampling mode in which the oscilloscope collects as many samples

as it can as the signal occurs.

Record Length

The number of waveform points used to create a record of a signal.

Rise Time

The time taken for the leading edge of a pulse to rise from itsminimum to its maximum values (typically measured from 10% to90% of these values).

Sample Point

The raw data from an ADC used to calculate waveform points.

Screen

The surface of the CRT upon which the visible pattern is produced -the display area.

Signal Generator

A test device for injecting a signal into a circuit input; the circuit'soutput is then read by an oscilloscope.

Sine Wave

A common curved wave shape that is mathematically defined.

Single Shot

A signal measured by an oscilloscope that only occurs once (alsocalled a transient event).

Single Sweep

A trigger mode for displaying one screenful of a signal and thenstopping.

Slope

On a graph or an oscilloscope screen, the ratio of a vertical distance to

a horizontal distance. A positive slope increases from left to right,while a negative slope decreases from left to right.

Square Wave

A common wave shape consisting of repeating square pulses.

Sweep

One horizontal pass of an oscilloscope's electron beam from left toright across the CRT screen.

Sweep Speed

Same as the time base.

Time Base

Oscilloscope circuitry that controls the timing of the sweep. The timebase is set by the seconds/division control.

Trace

The visible shapes drawn on a CRT by the movement of the electronbeam.

Transducer

A device that converts a specific physical quantity such as sound,pressure, strain, or light intensity into an electrical signal.

Transient

A signal measured by an oscilloscope that only occurs once (alsocalled a single-shot event).

Trigger

The circuit that initiates a horizontal sweep on an oscilloscope anddetermines the beginning point of the waveform.

Trigger Holdoff

A control that inhibits the trigger circuit from looking for a triggerlevel for some specified time after the end of the waveform.

Trigger Level

The voltage level that a trigger source signal must reach before thetrigger circuit initiates a sweep.

Volt

The unit of electric potential difference.

Voltage

The difference in electric potential, expressed in volts, between twopoints.

Waveform

A graphic representation of a voltage varying over time.

Waveform Point

A digital value that represents the voltage of a signal at a specific pointin time. Waveform points are calculated from sample points and storedin memory.

Z-axis

The signal in an oscilloscope that controls electron-beam brightness asthe trace is formed.

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NORMAL SWEEP DISPLAY OPERATION

a. Press the POWER switch to supply power, and the POWER LED lightsup.

b. A bright line appears in the CRT Centre. If it is not in the centre, adjustits position to the centre with the CH 1 POSITION controller. Then adjustthe brightness with the INTENSITY controller, and the focus with theFOCUS controller as required for easy observation.

c. Supply input signal into the CH1 INPUT jack. Rotate the VOLTS/DIVcontrol to adjust waveform to appropriate dimensions.

Set the MODE select switch to CH2. Then supply the inpu signal to theCH2 INPUT jack. Its waveform is displayed on the CRT in the sameprecedures with channel 1.

When the MODE select switch is set to ADD, the composite waveforms ofCH1 and CH2 (the algebric sum of CH1 + CH2) is displayed on the CRT.In this status, if CH2 INV is engaged by pulling out the CH2 POSITION,the algebriac difference between CH1 and CH2 (CH1-CH2) will bedisplayed.

The sensitivity of the ADDed waveform becomes the sames as the valueinficated by VOLT/DIV provided that the same as VOLTS/DIV value hasbeen set for the waveforms of the two channels.

When the MODE select swtich is set to ALT, the channel 1 and channel 2waveforms are displayed alternatively in every sweep. Waveforms of eachchannel is triggered independently. If the MODE select switch is set toCHOP, channel 1 and channel 2 waveforms through chopped triggering aredisplayed. If the SOURCE select switch is set to V.MODE, the channel 1signal only is triggered. To made the channel 2 signal triggered, set theSOURCE select switch to CH2.

The display on the screen will probably be unsynchronized. Refer toTRIGGERING procedure below for adjusting synchronization and sweepspeed to obtain a stable display showing the desired number of waveform.

TRIGGERING

The input signal must be properly triggered for stable waveformobservation. TRIGGERING is possible the input signal INTernally to createa trigger or with an EXTernally provided signal of timimng relationship tothe observed signal, applying such a signal to the EXT. TRIG INPUT jack.

1. The selection of a signal that serves as a trigger signal is made using theSOURCE switch.

Internal Sync

When the SOURCE selector is set to V.MODE, CH1, CH2, or LINE, theinput signal is connected to the internal trigger circuit. In this position, apart of the input signal is fed to the INPUT jack or is applied from thevertical amplifier to the trigger circuit to cause the trigger signalsynchronously with the input signal to drive the sweep circuit. If theSOURCE select switch is set to V.MODE, the trigger signal is selected incompliance with the vertical MODE selector setting. Setting the verticalMODE selector to ALT causes independent trigger to the channel 1 andchannel 2 signals respectively, enabling two signals with no timerelationship to be observed.

If the SOURCE select swtich is set to CH1 or CH2, triggering is made bythe channel 1 and channel 2 signals respectively, regardless of MODEsetting. Setting the SOURCE select switch to LINE causes synchronisationwith commercial power frequency.

External Sync

When the SOURCE selection is in EXT, th input signal at the EXT TRIGINPUT jack becomes the trigger. This signal must have a time or frequencyrelationship to the signal being observed to synchronise the display.External sync is preferred for waveform observation in many applications.For example, the figure below

shows that the sweep circuit is driven bt the gate signal when the gate signalin the burst signal is applied to the EXT. TRIG INPUT jack.

Shows the input/output signals, where the burst signal generated from thesignal is applied to the instrument under test. Thus, accurate triggering canbe achieved without regard to the input signal fed to the INPUT or jack sothat no further triggering is required even when the input signal is varied.

2. After the SOURCE has been set, the trigger point can be set by rotatingLEVEL/SLOPE control.

AC:

The trigger signal is capacitatively coupled, so its DC component is cut,giving a stable trigger which is not affected by the DC component. Withthis advantage, this position of the coupling switch is conveniently selectedfor ordinary applications. However, id the trigger signal is lower than 10Hz,the trigger signal level becomes attenuated, resulting in difficulty intriggering.

HFrej:

The trigger signal is supplied through a low pass filter to eliminate the highfrequency component (higher than 10 kHz), giving a stable triggering withlow frequency component. When high-frequency noise is superimposedover te trigger signal as shown in Fig 9, the high frequency noise is cut toprovide a stable trigger.

DC:

Permits triggering from DC to over 60MHz. Couples DC component ofsync trigger signal. Useful for triggering from very low frequency signals(below 10 Hz) ot ramp waveforms with slow repeating DC.

3. Setting of coupling switch.

Triggering Level

Trigger point on waveform is adjusted bt the LEVEL/PULL control. Figure10 shows the relationship between the SLOPE and LEVEL of the triggerpoint. Triggering level can be adjusted as necessary.

Auto Trigger

When the TRIG MODE selection is in AUTO, the sweep circuit becomesfree-running s long as there is no trigger signal, permitting a check of GNDlevel. When a trigger signal is present, the trigger point can be determinedbt the LEVEL control for observation as in the nornal trigger signal. Whenthe trigger level exceeds the trigger signal, the trigger circuit also becomesfree running where the waveform starts running. When the TRIG MODE isset to NORM and/or, when the trigger signal is absent or the triggeringlevel exceeds the signal there is no sweep.

Fix

When the TRIG MODE is set to FIX, triggering is always effected in thecenter of the waveform, eliminating the need for adjusting the triggeringlevel. As shown in Fig 11 (a) or (b), when the TRIG MODE is set toNORM and the triggering level is adjusted to either side of the signal, thetrigger point is deviated as the input signal becomes small which, in turn,stops the sweep operation. By setting the TRIG MODE to FIX, thetriggering level is automatically adjusted to the approximate centre of thewaveform and the signal is synchronised regardless of the poistion ofLEVEL control as shown in fig 11(c). When the input signal is suddenlychanged from a square waveform to a pulse waveform, the trigger point isshifted extremely towards the "-" side of the waveform unless the triggeringlevel is readjusted as shown in Fig 12(a).

See Fig 12(a)-(2). Also, if the trigger point has been set to the "-" ofsquarewave (Fig 12(b)-(1)) and the input signal is changed to a pulse signal,the trigger point is deviated and the sweep stops. When this happens, set the

TRIG MODE to FIX and the triggerring is effected in the approximatecentre of the waveform, making it possible to observe a stabilisedwaveform.

5. Adjust the A SWEEP/TIME DIV control to obtain an appropriatedisplay. Now a normal sweep display is obtained.

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MAGNIFIED SWEEP OPERATION

Since merely shortening the sweep time to magnify a portion of anobserved waveform can result in the desired position disappearing off thescreen, such magnified display should be performed using theMAGNIFIED SWEEP.

Using the Horizontal POSITION control, adjust the desired portion ofwaveform to the CRT. Pull the PULL X 10 MAG control to magnify thedisplay 10 times. For this type of display the sweep time is the SWEEPTIME/DIV setting divided by 10.

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ALTERNATE SWEEP OPERATION

A sweep and B delayed sweep are usable in an alternating fashion making itpossible to observe both the normal and magnified waveformsilmultaneously.

Procedure:

1. Set the HORIZ MODE to A and adjust for a normal waveform display.

2. Depress the HOLD OFF control and set the HORIZ MODE to ALT.Adjust TRACE SEPERATION for easy observation of both the A and Btraces. The upper trace is the non-magnified portion of the waveform withthe magnified portion super-imposed as an intensified section. The lovewaveform is the intensified portion displayed magnified.

3. The DELAY TIME POSITION control can be used to continuously slidethe magnified portion of the waveform across the A sweep period to allowmagnification or precisely the desired portion of waveform.

4. Set the HORIZ MODE to B to display the INT intensified portion as amagnified B sweep.

5. For starts AFTER DELAY operation, apparent jitter increases asmagnification increases. To obtaina jitter free display pull the HOLD OFFcontrol out. In this "Triggerable After Delay" moe the A trigger signalselected by the SOURCE switch becomes the B trigger source.

FIG11

FIG12

FIG 13

Note that for this type operation both the DELAY TIME POSITION andTRIG LEVEl affect the start of the B sweep so that the delay time is used asa reference point.

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X-Y OPERATION

For some measurements, an external horizontal deflection is required. Thisis also referred to as an X-Y measurement, where the Y input providesvertical deflection and X input provides horizontal deflection.

X-Y operation permist the oscilloscope to perform many types ofmeasurements not possible with conventional swep operation. The CRTdisplay becomes an electronic graph of two instantaneous voltages. Thedisplay may be a direct comparision of two voltages such as during phasemeasurement, or frequency measurement with Lissajous waveforms.

To use an external horizontal input, use the following procedure:

1. Set the HORIZ MODE switch to X-Y the position.

2. Use the channel 1 probe for the vertical input and the channel 2 probe forthe horizontal input.

3. Adjust the amouiunt of horizontal deflection with the CH2 VOLTS/DIVand VARIABLE controls.

4. The CH2 POSITION control now serves as the horizontal positioncontrol and the horizontal POSITION control is disabled.

5. All sync controls are disconnected and have no effect.

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SINGLE SWEEP OPERATION

This mode of display is useful for looking at non-synchronous or one timeevents.

Procedure:

1. Set the TRIF MODE to either AUTO or NORM. Apply a signal ofapproximately the same amplitude and frequency as the disnal thais is to beobeserved as he tridder signal and set the trigger level.

2. Set TEIG MODE to RESET - observe that the READY indicator LEDlights to indicate the reset condition. This LED goes out when the sweepperiod is completed.

3. After the above set up is completed the scope is ready to operate in theSINGLE sweep ,ode of operation after resetting the instrument using theRESET switch. Input of the trigger signal results in one and only one sweepand ready indicator LED goes out.

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DC VOLTAGE MEASUREMENT

To measure waveform DC level, carry out the following operations:

1. Connect the signal to be measured to the INPUT jack. For the channelwhich is selected by the vertical MODE switch, set the AC-GND-DCswitch to DC and adjust the controls for normal sweep. Then adjust theVOLTS/DIV and SWEEP TIME/DIV controls to the optimum settings formeasurement of the waveform.

2. Set the TRIG MODE switch to AUTO and AC-GND-DC switch toGND. The trace displayed at this time is the GND level (reference line).

Using the CH1 POSITION control, adjust the trace position to the desiredreference level position, making sure not to disturb this setting once made.

3. Set the AC-GND-DC switch to the DC position to observe the inputwaveform, including its DC component. If an appropriate reference level orVOLTS/DIV setting was not made, the waveform may not be visible on theCRT screen at this point. If so, reset VOLTS/DIV and/or the CH1POSITION control.

4. Use the horizontal POSITION control to bring the portion of thewaveform to be measured to the center vertical graduation line of the CRTscreen.

5. Measure the vertical distance from the reference level to the point to bemeasured, (the reference level can be rechecked by setting theAC-GND-DC switch again to GND).

To obtain the real voltage, multiply the vertical distance value by theVOLTS/DIV infication value. When a 10:1 probe is used, further multiplythe value by 10. Voltages above and below the reference level are positiveand negative values respectively.

When a 10:1 probe is used:

DC level = Vertical Distance (div) X VOLTS/DIV setting X 10

With direct measurement

DC level = Vertical distance in divisions X VOLTS/DIV setting X (probeattenuation ratio)

Example

For the example, the point being measured is 3.8 divisions from thereference level (ground potential).

If the VOLTS/DIV was set to 0.2 V and 10:1 probe was used.

Substituting the given values:

DC level = 3.8 (div) X 0.2 (V) X 10 = 7.6 V

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MEASUREMENT OF THE VOLTAGE BETWEENTWO POINTS ON THE WAVEFORM.

This technique can be used to measure peak to peak voltages.

1. Apply the signal to be measured to the INPUT jack. Set the verticalMODE to the channel to be used. Set the veritical MODE to the channel tobe used. Set the AC-GND-DC to AC, adjusting VOLTS/DIV and SWEEPTIME/DIV for a normal display. Set the VARIABLE control to CALposition.

2. Using the CH POSITION control, adjust the waveform position such thatone of the two points falls on a CRT graduation line and that the other isvisible on the display screen.

3. Using the horizontal POSITION control, adjust the second point toconincide with the centre vertical graduation line.

4. Measure the vertical distance between the two points and multiply this bythe setting of the VOLT/DIV control. When a 10:1 probe is used, furthermultiply the value by 10.

When a 10:1 probe is used.

Volts peak-to-peak = Vertical distance (div) X (VOLTS/DIV setting) X 10

With direct measurement

Voltage between 2 points = Vertical distance (div) x 2 points.

Example

For the example, the 2 points are seperated by 4.5 divisions vertically. Setthe VOLTS/DIV setting be 0.2 V/div and the probe attenuation be 10:1.

Substituting the given values:

Voltage between two points = 4.5 (div) X 0.2 (V/div) X 10 = 9.0 V

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ELIMINATION OF UNDESIRED SIGNALCOMPONENTS

The ADD feature can be conveniently used to cancel out the effect of anundesired signal component which superimposed on the signal you wish toobserve.

Procedure:

1. Apply the signal containing an undesired component to CH1 INPUT jackand the undesired signal itself alnoe to the CH2 INPUT jack.

2. Set the vertical MODE switch to CHOP and SOURCE switch to CH2.Verify that CH2 represents the unwanted signal in reverse polarity. Reversethe polarity by setting CH2 INV as required.

3. Set the vertical MODE to ADD, SOURCE to V.MODE and CH2VOLTS/DIV and VARIABLE so that the undesired signal component iscancelled as much as possible. The remaining signal you wish to observealone and free of the unwanted signal.

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TIME MEASUREMENTS

Time between two points on a wave can be measured fromthe SWEEPTIME/DIV value and horizontal distance between two points.

Procedure:

1. Apply the signal to be measured to the INPUT jack. Set the verticalMODE to the channel to be used. Set the AC-GND-DC to DC, adjustingVOLTS/DIV and SWEEP TIME/DIV for a normal display. Set theVARIABLE control to CAL position.

2. Horizontal position control set to this point at the intersection of anyvertical graduation line. Using the CH POSITION control, set one of thepoints to be used as a reference to conincide with the horizontal centerline.

3. Measure the horizontal distance between the two points. Multiply this bythe setting of the SWEEP TIME/DIV control to obtain the time between thetwo points. If horizontal "X 10 MAG" is used, multiply this further by 1/10.

Using the formula :

Time = horizontal distance (div) X (SWEEP TIM/DIV setting) / "X 10"value

Example

For the example, the horizontal distance between the 2 points is 5.4 sweepdivisions. If the SWEEP TIME/DIV is 0.2ms/div we calculate.

Substituting the given value:

Time = 5.4 div X 0.2 ms/div = 1.08ms

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TIME DIFFERENCE MEASUREMENTS

Time difference between two synchronised signals can be measured asfollows:

Procedure:

1. Apply the 2 signals to CH1 and CH2 INPUT jacks. Setting the verticalMODE to either ALT or CHOP mode. Generally for low frequency signalsCHOP is chosen with ALT used for high frrequency signals.

2. Select the faster of the two signals as the SOURCE and use theVOLTS/DIV and SWEEP TIME/DIV to obtain an easily observed display.

Set the VARIABLE control to CAL position.

3. Using the vertical POSITION control set the waveform to the center ofthe CRT display and use the horizontal POSITION control to set thereference signal to be coincident with a vertical graduation line.

4. Measure the horizontal distance between the two signals and multiplythis distance in division by the SWEEP TIME/DIV setting.

If "X 10 MAG" is being used multiply this again by 1/10.

Using the formula:

Time = Horizontal distance X (SWEEP TIME/DIV setting) / "X10 MAG"value

Example

For the example, when the horizontal distance between two signals is 4.4divisions. The SWEEP TIME/DIV is 0.2 (ms/div)


Time = 4.4 (div) X 0.2 (ms/div) = 0.88ms

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PULSE WIDTH MEASUREMENTS

Pulse width can be measured as follows:

Procedure:

1. Apply the pulse signal to the INPUT jack. Set the vertical MODE switchto the channel to be used.

2. Use the VOLTS/DIV, VARIABLE and vertical POSITION to adjust thewaveform such that the pulse is easily observed and such that the centerpulse width conincides with the center horizontal line on the CRT screen.

3. Set the SWEEP VARIABLE switch to CAL. Measurement the horizontaldistance between the intersections of the pulse waveform and CRT centerhorizontal line in divisions, and multiply the measured distance by the valueindicatedby SWEEP TIME/DIV. If the "X10 MAG" mode is being used,also multiply the product by 1/10.

Using the formula:

Pulse width = Horizontal distance (div) X (SWEEP TIME/DIV setting) /"X10 MAG" value.

Example

For the example, the distance at the center horizontal line is 4.6 divisionsand the SWEEP TIME/DIV is 0.2 (ms/div)


Pulse width = 4.6 (div) X 0.2 (ms/div) = 0.92 ms

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PULSE RISETIME AND FALLTIMEMEASUREMENTS

For risetime and falltime measurements, the 10% and 90% amplitude pointsare used as starting and ending reference points.

Procedure:

1. Apply a signal to the INPUT jack. Set the vertical MODE to the channelto be used.

Use the VOLTS/DIV and VARIABLE to adjust the waveform peak-to-peakheight to five divisions.

2. Using the vertical POSITION control and the other controls, adjust thedisplay sich that the wavedoem is centered vertically in the display. Set theSWEEP TIME/DIV to as fast a setting as possible consistent withobservation of both the 10% and 90% points. Set the SWEEP VARIABLEcontrol to CAL position.

3. Use the horizontal POSITION control to adjust the 10% point to coincidewith a vertical graduation line and measure the distance in divisionsbetween the 10% and 90% points on the waveform. Multiply this by theSWEEP TIME/DIV and also by 1/10 if "X10MAG" mode was used.

NOTE:

The graticule on the CRT includes the 0, 10, 90, and 100 % lines assumingthat 5 divisions correspond to 100 %. Use them as a reference for accuratemeasurements.

Using the formula:

Risetime = Horizontal distance (div) X (SWEEP TIME/DIV setting) / "X10MAG" value.

Example

For the example, the horizontal distance is 3.3 divisions. The SWEEPTIME/DIV is 2 (us/div)


Risetime = 3.3 (div) X 2 (us/div) = 6.6 us

Risetime and falltime can be measured by making use of the alternate step 3as described below as well.

4. Use the Horizontal POSITION control to set the 10% point to coincidewith the center vertical graduation line and measure the horizontal distanceto the point of the intersection of the waveform with the center horizontalline. Let this distance be D1. Next adjust the waveform position such thatthe 90% point coincides with the vertical centerline and measure thedistance from that line to the intersection of the waveform with thehorizontal centerline. This distance is D2 and the total horizontal distance isthen D1 plus D2 for use in the above relationship in calculating the risetime

or falltime.

Using the formula:

Risetime = (D1 + D2) (div) X (SWEEP TIME/DIV setting) / "X10 MAG"value.

Example

For the example, the measured D1 is 1.6 divisions while D2 is 1.4divisions. If SWEEP TIME/DIV is 2 us/div we use the followingrelationship.


Risetime = (1.6 + 1.4) (div) X 2 (us/div) = 6 us

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PHASE DIFFERENCE MEASUREMENTS

Phase difference between two sine waves of the same frequency can bemeasured as follows:

Procedure:

1. Apply the 2 signals to the CH1 and CH2 INPUT jacks, setting thevertical MODE to either CHOP or ALT mode.

2. Set the controls to obtain normal sweep. Set the SOURCE switch toselect the signal which is leading in phase, and adjust the VOLTS/DIV andvertical VARIABLE controls such that the two signals are equal inamplitude.

3. Use the SWEEP TIME/DIV and SWEEP VARIABLE to adjust thedisplay such that one cycle of the signals occupies 8 divisions of horizontaldisplay.

Operate the vertical POSITION to shift the two signals on the center of thescale.

Having set up the display as above, one division now represents 45 degreesin phase.

4. Measure the horizontal distance between corresponding points on the twowaveforms.

Using the formula:

Phase difference = Horizontal distance (div) X 45 degrees/div

Example

For the example, the horizontal distance is 1.7 divisions.


The phase difference = 1.7 (div) X 45 degrees/div = 76.5 degrees.

The above setup allows 45 degrees per division but if more accuracy isrequired the SWEEP TIME/DIV may be changed and magnified withouttouching the VARIABLE control and if necessat the trigger level can bereadjusted.

In this case, the phase difference can be obtained from the SWEEPTIME/DIV setting for 8 divisions.cycle and the new SWEEP TIME/DIVsetting changed for higher accuracym by using the following formula:

Phase difference = Horizontal distance of new sweep range X 45degrees/div

X New SWEEP TIME/DIV setting

Original SWEEP TIME/DIV setting

Another simple method of obtaining more accuracy quickly is to simply useX 10 MAG for a scale of 4.5 degrees/division.

One cycle adjusted to occupy 8 div

Expanded sweep waveform display.

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FREQUENCY MEASUREMENTS

Frequency measurement are made by measuring the period of one cycle ofwaveform and taking the reciprocal of this time value as the frequency.

Procedure

1. Following the procedure described in section 5 "Time Measurement",measure the time of each cycle. The figure obtained in the signal period.

2. Frequency is the the reciprocal of the period measured.

Using the formula:

Frequency = 1/period.

Example

A period of 40us is observed and measured.

Assuming that SWEEP TIME/DIV indicated 5 us/div, sustituting the givenvalue:

Frequency = 1/(40us) = 25 kHz

While the above method relies on the measurement directly of the period ofone cycle, the frequency may also be measured by counting the number ofcycles present in a given time period.

1. Apply the signal to the INPUT jack. Set the vertical MODE to thechannel to be used and adjusting the various controls for a normal display.Set the VARIABLE control to CAL position.

2. Count the number of cycles of waveform between a chosen set ofgraticules in the vertical axis direction. Using the horizontal distancebetween the vertical lines used above and the SWEEP TIME/DIV, the timespan may be calculated. Multiply the reciprocal of this value by the numberof cycles present in the given time span. If "X10 MAG" is used multiplythis by a further 10.

Note that errors will only occur for displays having only a few cycles.

Using the formula :

Frequency =

Example

For the example, within 7 divisions, there are 10 cycles. The SWEEPTIME/DIV is 5us/div.


Freq =

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RELATIVE MEASUREMENTS

If the frequency and amplitude of some reference signals are known, anunknown signal may be measured for level and frequency without use ofthe VOLTS/DIV or SWEEP TIME/DIV for calibration.

The measurement is made in units relative tothe reference signal.

Vertical sensitivity

Setting the relative vertical sensitivity using a reference signal.

Procedure:

1. Apply the reference signal to the INPUT jack and adjust the display for anormal waveform display.

Adjust the VOLTS/DIV and VARIABLE so that the signal conincides withthe CRT face's graduation lines. After adjusting, be sure not to disturb thesetting of the VARIABLE control.

2. The vertical calibration coefficient is now the reference signal'samplitude (in volts) divided by the product of the vertical amplitude set instep 1 and the VOLTS/DIV setting.

Using the formula:

Vertical coefficient= Voltage of the ref signal/vertical amplitude

3. Remove the reference signal and apply the unknown signal to the INPUTjack, using the VOLTS/DIV control to adjust the display for easyobservation. Measure the amplitude of the displayed waveform and use thefollowing relationship to calculate the actual amplitude of the unknownwaveform.

Using the formula

Amplitude of the unknown signal =

Example

For the example, the VOLTS/DIV is 1V/div.

The reference signal is 2 Vrms. Using the VARIABLE, adjust so that theamplitude of the reference signal is 4 divisions.


Vertical coefficient =

Then measure the unknown signal and VOLTS/DIV is 5V and verticalamplitude is 3 divisions.


Effective value of unknown signal = 3 (div) X 0.5 X 5

Period

Setting the relative sweep coefficient with respect to a reference frequencysignal.

Procedure:

1. Appy the reference signal to the INPUT jack, using the VOLTS/DIV andVARIABLE to obtain an easily observed waveform display.

Using the SWEEP TIME/DIV and VARIABLE adjust one cycle of thereference signal to occupy a fixed number of scale divisions accurately.After this is done be sure not to disturb the setting of the VARIABLEcontrol.

2. The sweep (horizontal) calibration coefficient is then the period of thereference signal divided bt the product of the number of divisions used instep 1 for setup of the reference and seting of the SWEEP TIME/DIVcontrol.

Using the formula:

Sweep coefficient =

3. Remove the reference signal and input the unknown signal, adjusting theSWEEP TIME/DIV conrtol for easy observation.

Measure the width of one cycle in divisions and use the followingrelationship to calculate the actual period.

Using the formula:

Period of unknown signal =

Example

SWEEP TIME/DIV is 0.1 ms and apply 1.75 kHz reference signal. Adjustthe VARIABLE so the the distance of one cycle is 5 divisions.

Substituting the given values.

Horizontal coefficient =

Then, SWEEP TIME/DIV is 0.2 and horizontal amplitude is 7 div


Pulse width = 7 (div) X 1.143 X 0.2 = 1.6 ms

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SWEEP MULTIPLICATION (MAGNIFICATION)

The apparent magnification of the delayed sweep is determined by thevalues set by the A and B SWEEP TIME/DIV controls.

1. Apply a signal to the INPUT jack and set the vertical MODE tothechannel to be used, adjusting the VOLTS/DIV for an easily observeddisplay of the waveform and the other controls if necessary.

2 Set the A SWEEP TIME/DIV so that several cycles of the waveform aredisplayed. Depress the HOLD OFF control to (AFTER DELAY).

When the HORIZ MODE is set to INT, the magnified portion of thewaveform will appear intensified o the CRT display.

3. Use the DELAY TIME MULT to shift the internsified porttion of thewaveform to correspond with the section to be magnified for observation.Use the B SWEEP TIME/DIV to adjust the intesified portion to cover theentire portion to be magnified.

4. Set the HORIZ MODE to either ALT or B and use the POSITION andTRACE SEPERATION controls to adjust the display for easy viewing.

5. Time measuements are performed in the same manner from the B sweepas was described above for A sweep time measurements.

The apparent magnification of the intensified waveform section is tha ASWEEP TIME/DIV divided by the B SWEEP TIME/DIV.

Using the formula:

The apparent Magnification

of the Intensified Waveform

Example:

In the example, the A SWEEP TIME is 2us and the B SWEEP TIME is 0.2us.


Apparent magnification ratio:

With the above magnification, if the magnification ratio is increased, delayjitter will occur.

To achieve a stable display, set the B MODE to TRIG and used thetriggered mode of operation.

1. Perform the above steps 1 through 3.

2. Pull the HOLD OFF control to activate B TRIG'D function.

3. Set the HORIZ MODE to either ALT or B. The apparent magnificationwill be the same as described above.

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APPLICATION OF X-Y OPERATION

Phase shift measurement

A method of phase measurement requires calculations based on theLissajous patterns obtained using X-Y operations. Distortions due to anon-linear amplification also can be displayed.

A sine wave input is applied to the audio circuit being tested. The same sinewave input is applied to the vertical input of the oscilloscope, and theoutput of the tested circuit is applied to the horizontal input of theoscilloscope. The amount of phase difference between the two signals canbe calculated from the resulting waveform.

To make phase measurements, use the following procedure.

1. Using an audio signal generator witha a pure sinosoidal signal, apply asine wave test signal at the desired test frequency to the audio networkbeing tested.

2. Set the signal generator output for the normal operating level of thecircuit being tested. If desired, the circuit's output may be observed on theoscilloscope. If the test circuit is overdriven, the sine wave display on theoscilloscope is clipped and the signal level must be reduced.

3. Connect the channel 2 probe to the output of the test circuit.

4. Select X-Y operation by placing the TRIG MODE switch in the X-Yposition.

5. Connect the channel 1 probe to the input of the test circuit.

(The input and output test connections to the vertical and horizontaloscilloscope inputs may be reserved).

6. Adjust the channel 1 and 2 gain controls for a suitable viewing size.

7. Some typical results are shown in Fig 4.7.

If the two signals are in phase, the oscilloscope trace is straight diagonalline. If the vertical and horizontal gain are properly adjusted, this like is at a45 degree angle. A 90degree phase shift produces a circular oscilloscopepattern.

Phase shift of less that 90 degrees produces an elliptical oscilloscopepattern. the amoint of phase shift can be calculated from the oscilloscopetrace as shown in Fig below.

Frequency measurement

1. Connect the sine wave of known frequency to the channel 2 input jack ofthe oscilloscope and select X-Y operation. This provides external horizontal

input.

2. Connect the vertical input probe (CH1 INPUT) to the unknownfrequency.

3. Adjust the channel 1 and 2 size controls for convenient, easy to read sizeof display.

4. The resulting pattern, called a Lissajous pattern, shows the ratio betweenthe two frequncies.

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