1 cathode ray oscilloscope introduction look and play look and play read instructions read...

27
1 Cathode Ray Oscilloscope Cathode Ray Oscilloscope Introduction Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts Decide on a simple measurement Decide on a simple measurement Increase your level of difficulty Increase your level of difficulty Record pathway. How you got Record pathway. How you got there. there. Store directions and short-cuts Store directions and short-cuts

Upload: anissa-fitzgerald

Post on 27-Dec-2015

214 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

1

Cathode Ray Cathode Ray Oscilloscope Oscilloscope Introduction Introduction

Look and playLook and play Read instructionsRead instructions Break into smaller partsBreak into smaller parts Decide on a simple measurementDecide on a simple measurement Increase your level of difficultyIncrease your level of difficulty Record pathway. How you got there.Record pathway. How you got there. Store directions and short-cutsStore directions and short-cuts

Page 2: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

2

Cathode Ray Cathode Ray OscilloscopeOscilloscope

Popular instrument to show time, Popular instrument to show time, voltage both DC and AC. Shows Volts voltage both DC and AC. Shows Volts / Time./ Time.

Display waveforms. Display waveforms. Spectrum scope shows volts to Spectrum scope shows volts to FrequencyFrequency

Cathode (-ve ) is heated, emits Cathode (-ve ) is heated, emits electrons, accelerated toward a (+ve) electrons, accelerated toward a (+ve) fluorescent screen. fluorescent screen. Intensity grid, Focus Intensity grid, Focus grid, Accelerating anode. (Electron gun)grid, Accelerating anode. (Electron gun)

Horizontal deflection plates.Horizontal deflection plates. Vertical deflection plates Vertical deflection plates

Page 3: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

3

Cathode Ray Cathode Ray OscilloscopeOscilloscope

When electrons hit the screen the When electrons hit the screen the phosphor is excited and emits light. phosphor is excited and emits light.

Persistence. How long the display glows.Persistence. How long the display glows. May need to reduce ambient light for May need to reduce ambient light for

older instruments.older instruments. Connect a signal to Vertical deflection Connect a signal to Vertical deflection

plate. plate. At same time a voltage that increases At same time a voltage that increases

linearly with time (Ramp) is applied to linearly with time (Ramp) is applied to the Horizontal deflection plates.the Horizontal deflection plates.

Page 4: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

4

This horizontal linear deflection is This horizontal linear deflection is produced by the Sweep generator.produced by the Sweep generator.

Sawtooth wave.Sawtooth wave.

When the sweep signal returns to When the sweep signal returns to

zero ie the end of the sweep, the zero ie the end of the sweep, the beam flies back to the start beam flies back to the start position. The beam is cut off during position. The beam is cut off during the flyback time.the flyback time.

Page 5: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

5

CROsCROs

The display is made to appear The display is made to appear stationary.stationary.

This controlled by your adjustment This controlled by your adjustment settings.settings.

The eye sees a waveform.The eye sees a waveform. X is <----> Horizontal X is <----> Horizontal Y is ^ Vertical Height of traceY is ^ Vertical Height of trace

Page 6: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

6

The signal is amplified by the vertical The signal is amplified by the vertical amplifier, applied to the vertical plates.amplifier, applied to the vertical plates.

A portion of the vertical amp signal is A portion of the vertical amp signal is applied to the Sweep Trigger.applied to the Sweep Trigger.

The sweep trigger generates a pulse The sweep trigger generates a pulse coincident with a selected point in the coincident with a selected point in the cycle of the trigger signal.cycle of the trigger signal.

This pulse turns on the sweep generator This pulse turns on the sweep generator initiating the sawtooth wave form.initiating the sawtooth wave form.

The sawtooth wave is amplified by the The sawtooth wave is amplified by the horizontal amp and applied to the horizontal amp and applied to the horizontal deflection plateshorizontal deflection plates

Page 7: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

7

The trigger can be based on 50 The trigger can be based on 50 (60) Hz(60) Hz

Provision is made for an external Provision is made for an external

trigger.trigger.

Page 8: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

8

CRO Tube CRO Tube ControlsControls

POWER POWER on / off on / off ScaleScale IlluminationIllumination FocusFocus. Create spot on screen. Create spot on screen IntensityIntensity. Brightness (Don’t burn . Brightness (Don’t burn

a spot on your screen)a spot on your screen)

Page 9: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

9

Vertical AmpVertical Amp PositionPosition on display on display SensitivitySensitivity of vertical amp of vertical amp

Calibrated. Cal fully clockwise.Calibrated. Cal fully clockwise. VariableVariable sensitivity. Continuous range between sensitivity. Continuous range between

calibrated steps.calibrated steps.

AC - DC - GndAC - DC - Gnd.. Selects desired coupling for incoming signal, or Selects desired coupling for incoming signal, or

grounds amp input. DC couples signal directly to grounds amp input. DC couples signal directly to amp. AC connects via a capacitor. (Blocks DC) amp. AC connects via a capacitor. (Blocks DC)

Gnd = no signal. Gnd connects Y input to 0 volts. Gnd = no signal. Gnd connects Y input to 0 volts.

Checks position of 0v on screenChecks position of 0v on screen..

Page 10: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

10

Horizontal Horizontal SweepSweep

Sweep time / Div (or CM)Sweep time / Div (or CM) Select Select desired sweep rate, or admits external desired sweep rate, or admits external sig to horiz amp.sig to horiz amp.

Sweep time / Cm VariableSweep time / Cm Variable Continuously variable sweep rates.Continuously variable sweep rates. Cal is Cal is fully clockwise.fully clockwise.

PositionPosition Controls horizontal position Controls horizontal position of trace.of trace.

Horizontal variableHorizontal variable controls controls attenuation of signal applied to Horz amp attenuation of signal applied to Horz amp through Ext Horiz connector. through Ext Horiz connector.

Page 11: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

11

Trigger Trigger Set to Auto Set to Auto or normalor normal

TriggerTrigger selects timing of the selects timing of the beginning of the Horizontal sweep.beginning of the Horizontal sweep.

SlopeSlope selects trigger at +ve increasing or selects trigger at +ve increasing or -ve decreasing portion of signal.-ve decreasing portion of signal.

CouplingCoupling Selects whether trigger is at a Selects whether trigger is at a specific DC or AC level.specific DC or AC level.

Source: Source: IntInt from Vertical Amp from Vertical Amp ExtExt from Ext Trig Input. from Ext Trig Input. LineLine AC line 50 (60) HZ AC line 50 (60) HZ

Page 12: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

12

Volts /Div switchVolts /Div switch

Volts / DivVolts / Div VariableVariable Fine adjustment Fine adjustment these controls can have a Pull out these controls can have a Pull out

switch position. May be 5 times mag.switch position. May be 5 times mag.

Page 13: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

13

Vertical modeVertical mode

The operation of vertical deflection The operation of vertical deflection platesplates

Chan 1 and Chan 2 can each operate Chan 1 and Chan 2 can each operate separately.separately.

Dual. Ch1 and Ch2 are swept Dual. Ch1 and Ch2 are swept alternatively.alternatively.

Why Dual? Used to measure input and Why Dual? Used to measure input and Output signals of a device under test.Output signals of a device under test.

Ch1 and Ch2 can be added Ch1 and Ch2 can be added

Page 14: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

14

Time baseTime base Main, Max, Min, delayMain, Max, Min, delay.. Selects the sweep for the main mix or delay mode and Selects the sweep for the main mix or delay mode and

also X-Y switchalso X-Y switch

Time/Div provides selection of sweep Time/Div provides selection of sweep rates. Range of 0.1 Second, 50 to .1 mS, rates. Range of 0.1 Second, 50 to .1 mS, 50 to 0.1uS per div. Note 5,2,1, sequence.50 to 0.1uS per div. Note 5,2,1, sequence.

To determine a frequency use reciprocal.To determine a frequency use reciprocal. Frequency = 1/time period Frequency = 1/time period (50Hz = 1/20mS)(50Hz = 1/20mS)

Time period = 1/Frequency Time period = 1/Frequency (number of div * ?ms/div. (number of div * ?ms/div. Eg 4div*5ms/div = 20 ms)Eg 4div*5ms/div = 20 ms)

Page 15: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

15

Other Other

Comp TestComp Test. Allows individual . Allows individual components to be tested. Connect components to be tested. Connect via banana jacks to test resistors, via banana jacks to test resistors, capacitors, diodes, transistors, etccapacitors, diodes, transistors, etc

Cal Cal delivers calibrated voltage e.g. delivers calibrated voltage e.g. 2v p-p 1KHz square wave for setting 2v p-p 1KHz square wave for setting scale.scale.

GNDGND. Earth terminal of scope. Earth terminal of scope

Page 16: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

16

ConnectionsConnections

Vertical InputVertical Input Horizontal InputHorizontal Input External TriggerExternal Trigger Cal. OutCal. Out

Page 17: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

17

BandwidthBandwidth A 10MHz CRO does not mean it will correctly measure A 10MHz CRO does not mean it will correctly measure

signals at 10MHz.signals at 10MHz. Vertical Amps are not so wide-band as to amplify all Vertical Amps are not so wide-band as to amplify all

signals. 10MHz is the 3dB point. A 10MHz signal of 1v signals. 10MHz is the 3dB point. A 10MHz signal of 1v will measure 0.707v on the screen.will measure 0.707v on the screen.

Clipping introduces odd order harmonics. A CRO Clipping introduces odd order harmonics. A CRO operating near the max freq. will not show the operating near the max freq. will not show the harmonics and you think you are reading a clean harmonics and you think you are reading a clean

signal.signal. Square waves begin to look like sine waves.Square waves begin to look like sine waves. A rule of thumb is 5 times. To measure 2MHZ use a A rule of thumb is 5 times. To measure 2MHZ use a

10MHz CRO. 3 times is suitable for most Amateur 10MHz CRO. 3 times is suitable for most Amateur work.work.

For 7MHz. Times 3 = 21. Use a 20 MHz CRO.For 7MHz. Times 3 = 21. Use a 20 MHz CRO.

Page 18: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

18

Every CRO will be Every CRO will be differentdifferent

Many instruments made for specific Many instruments made for specific work.work.

Beam Finder push buttonBeam Finder push button Trace rotationTrace rotation Chan 1 Vertical input. During X-Y Chan 1 Vertical input. During X-Y

operation this is X axis (abscissa)operation this is X axis (abscissa) Chan 2 Vertical input Chan 2. During Chan 2 Vertical input Chan 2. During

X-Y this becomes ordinate input.X-Y this becomes ordinate input.

Page 19: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

19

And there’s more And there’s more !!

Don’t worry about itDon’t worry about it Nothing is complexNothing is complex Just Simplicity multipliedJust Simplicity multiplied

Page 20: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

20

OperatingOperating

Power onPower on Intensity fully counter-clockwiseIntensity fully counter-clockwise Vertical centering in center of rangeVertical centering in center of range Horizontal centering in center of rangeHorizontal centering in center of range Vertical at 0.2 or 5v / div. Try a range. Vertical at 0.2 or 5v / div. Try a range. Timebase 10ms / div Change to suit.Timebase 10ms / div Change to suit. Play ‘till operating for you.Play ‘till operating for you.

Page 21: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

21

Mini exercisesMini exercises

Obtain a trace Obtain a trace BrightnessBrightness FocusFocus Move trace up, down.Move trace up, down. Move trace side waysMove trace side ways

Page 22: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

22

MeasuringMeasuring

Voltage RMS is 0.707 * Vp for Sine Voltage RMS is 0.707 * Vp for Sine and Cosine waveforms.and Cosine waveforms.

HintHint: Try using a multimeter in : Try using a multimeter in parallel until you are happy with the parallel until you are happy with the measured CRO readings. measured CRO readings.

Page 23: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

23

Mini exercise DCMini exercise DC Find a battery or a plugpack Find a battery or a plugpack (Wall wart)(Wall wart)

Determine approximate number of voltsDetermine approximate number of volts Set vertical amp. Volts per DivisionSet vertical amp. Volts per Division Cal. Control fully clockwiseCal. Control fully clockwise DC (AC will show ripple component DC (AC will show ripple component

only)only) Connect probe to batteryConnect probe to battery Read volts by number of volts per Read volts by number of volts per

division on display.division on display.

Page 24: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

24

AC Sine-waveAC Sine-wave Decide upon probable frequencyDecide upon probable frequency Set timebaseSet timebase Obtain displayObtain display DC or AC ??DC or AC ?? One or more cycles per division or One or more cycles per division or

whole display?whole display? Volts per division (Vertical) Peak to Volts per division (Vertical) Peak to

Peak Peak Calculate RMS volts (Peak x 0.707) Calculate RMS volts (Peak x 0.707)

Page 25: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

25

Square waveSquare wave Decide upon probable pulses per Decide upon probable pulses per

secondsecond Set timebase, Obtain display.Set timebase, Obtain display. One or more pulses per division or One or more pulses per division or

whole display?whole display? DC or AC ??? Try it.DC or AC ??? Try it. Volts per division. VerticalVolts per division. Vertical Pulses per division. Horizontal Pulses per division. Horizontal Measure volts, Length of pulse. Measure volts, Length of pulse.

Page 26: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

26

Complex wavesComplex waves AC ripple super imposed on a DC AC ripple super imposed on a DC

supplysupply Mixing two sine waves. Phase Mixing two sine waves. Phase

measurements. Lissajous patterns (X-measurements. Lissajous patterns (X-Y)Y)

Dual trace CROsDual trace CROs External Trigger ( Positive going and External Trigger ( Positive going and

Negative going)Negative going) Noise Noise Frequency resolution of CROs.Frequency resolution of CROs.

Page 27: 1 Cathode Ray Oscilloscope Introduction Look and play Look and play Read instructions Read instructions Break into smaller parts Break into smaller parts

27

Read your operating Read your operating manualmanual

Read your operating manualRead your operating manual Read your operating manualRead your operating manual Enjoy reading your operating Enjoy reading your operating

manual.manual. Test old projects, AM radios. Test old projects, AM radios. Audio or RF oscillatorsAudio or RF oscillators Read your operating manual - Read your operating manual -

ENJOYENJOY