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

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cathode ray oscilloscope introduction
Cathode Ray Oscilloscope Introduction
  • Look and play
  • Read instructions
  • Break into smaller parts
  • Decide on a simple measurement
  • Increase your level of difficulty
  • Record pathway. How you got there.
  • Store directions and short-cuts
cathode ray oscilloscope
Cathode Ray Oscilloscope
  • Popular instrument to show time, voltage both DC and AC. Shows Volts / Time.
  • Display waveforms. Spectrum scope shows volts to Frequency
  • Cathode (-ve ) is heated, emits electrons, accelerated toward a (+ve) fluorescent screen. Intensity grid, Focus grid, Accelerating anode. (Electron gun)
  • Horizontal deflection plates.
  • Vertical deflection plates
cathode ray oscilloscope3
Cathode Ray Oscilloscope
  • When electrons hit the screen the phosphor is excited and emits light.
  • Persistence. How long the display glows.
  • May need to reduce ambient light for older instruments.
  • Connect a signal to Vertical deflection plate.
  • At same time a voltage that increases linearly with time (Ramp) is applied to the Horizontal deflection plates.
This horizontal linear deflection is produced by the Sweep generator.
  • Sawtooth wave.
  • When the sweep signal returns to zero ie the end of the sweep, the beam flies back to the start position. The beam is cut off during the flyback time.
  • The display is made to appear stationary.
  • This controlled by your adjustment settings.
  • The eye sees a waveform.
  • X is <----> Horizontal
  • Y is ^ Vertical Height of trace
The signal is amplified by the vertical amplifier, applied to the vertical plates.
  • A portion of the vertical amp signal is applied to the Sweep Trigger.
  • The sweep trigger generates a pulse coincident with a selected point in the cycle of the trigger signal.
  • This pulse turns on the sweep generator initiating the sawtooth wave form.
  • The sawtooth wave is amplified by the horizontal amp and applied to the horizontal deflection plates
The trigger can be based on 50 (60) Hz
  • Provision is made for an external trigger.
cro tube controls
CRO Tube Controls
  • POWER on / off
  • Scale
  • Illumination
  • Focus. Create spot on screen
  • Intensity. Brightness (Don’t burn a spot on your screen)
vertical amp
Vertical Amp
  • Position on display
  • Sensitivity of vertical amp Calibrated. Cal fully clockwise.
  • Variable sensitivity. Continuous range between calibrated steps.
  • AC - DC - Gnd.
  • Selects desired coupling for incoming signal, or grounds amp input. DC couples signal directly to amp. AC connects via a capacitor. (Blocks DC)
  • Gnd = no signal. Gnd connects Y input to 0 volts. Checks position of 0v on screen.
horizontal sweep
Horizontal Sweep
  • Sweep time / Div (or CM)Select desired sweep rate, or admits external sig to horiz amp.
  • Sweep time / Cm VariableContinuously variable sweep rates. Cal is fully clockwise.
  • PositionControls horizontal position of trace.
  • Horizontal variablecontrols attenuation of signal applied to Horz amp through Ext Horiz connector.
trigger set to auto or normal
Trigger Set to Auto or normal
  • Trigger selects timing of the beginning of the Horizontal sweep.
  • Slopeselects trigger at +ve increasing or -ve decreasing portion of signal.
  • CouplingSelects whether trigger is at a specific DC or AC level.
  • Source: Int from Vertical Amp
  • Ext from Ext Trig Input.
  • Line AC line 50 (60) HZ
volts div switch
Volts /Div switch
  • Volts / Div
  • Variable Fine adjustment
  • these controls can have a Pull out switch position. May be 5 times mag.
vertical mode
Vertical mode
  • The operation of vertical deflection plates
  • Chan 1 and Chan 2 can each operate separately.
  • Dual. Ch1 and Ch2 are swept alternatively.
  • Why Dual? Used to measure input and Output signals of a device under test.
  • Ch1 and Ch2 can be added
time base
Time base
  • Main, Max, Min, delay.
  • Selects the sweep for the main mix or delay mode and also X-Y switch
  • Time/Div provides selection of sweep rates. Range of 0.1 Second, 50 to .1 mS, 50 to 0.1uS per div. Note 5,2,1, sequence.
  • To determine a frequency use reciprocal.
  • Frequency = 1/time period (50Hz = 1/20mS)
  • Time period = 1/Frequency (number of div * ?ms/div. Eg 4div*5ms/div = 20 ms)
  • Comp Test. Allows individual components to be tested. Connect via banana jacks to test resistors, capacitors, diodes, transistors, etc
  • Cal delivers calibrated voltage e.g. 2v p-p 1KHz square wave for setting scale.
  • GND. Earth terminal of scope
  • Vertical Input
  • Horizontal Input
  • External Trigger
  • Cal. Out
  • A 10MHz CRO does not mean it will correctly measure signals at 10MHz.
  • Vertical Amps are not so wide-band as to amplify all signals. 10MHz is the 3dB point. A 10MHz signal of 1v will measure 0.707v on the screen.
  • Clipping introduces odd order harmonics. A CRO operating near the max freq. will not show the harmonics and you think you are reading a clean signal.
  • Square waves begin to look like sine waves.
  • A rule of thumb is 5 times. To measure 2MHZ use a 10MHz CRO. 3 times is suitable for most Amateur work.
  • For 7MHz. Times 3 = 21. Use a 20 MHz CRO.
every cro will be different
Every CRO will be different
  • Many instruments made for specific work.
  • Beam Finder push button
  • Trace rotation
  • Chan 1 Vertical input. During X-Y operation this is X axis (abscissa)
  • Chan 2 Vertical input Chan 2. During X-Y this becomes ordinate input.
and there s more
And there’s more !
  • Don’t worry about it
  • Nothing is complex
  • Just Simplicity multiplied
  • Power on
  • Intensity fully counter-clockwise
  • Vertical centering in center of range
  • Horizontal centering in center of range
  • Vertical at 0.2 or 5v / div. Try a range.
  • Timebase 10ms / div Change to suit.
  • Play ‘till operating for you.
mini exercises
Mini exercises
  • Obtain a trace
  • Brightness
  • Focus
  • Move trace up, down.
  • Move trace side ways
  • Voltage RMS is 0.707 * Vp for Sine and Cosine waveforms.
  • Hint: Try using a multimeter in parallel until you are happy with the measured CRO readings.
mini exercise dc
Mini exercise DC
  • Find a battery or a plugpack (Wall wart)
  • Determine approximate number of volts
  • Set vertical amp. Volts per Division
  • Cal. Control fully clockwise
  • DC (AC will show ripple component only)
  • Connect probe to battery
  • Read volts by number of volts per division on display.
ac sine wave
AC Sine-wave
  • Decide upon probable frequency
  • Set timebase
  • Obtain display
  • DC or AC ??
  • One or more cycles per division or whole display?
  • Volts per division (Vertical) Peak to Peak
  • Calculate RMS volts (Peak x 0.707)
square wave
Square wave
  • Decide upon probable pulses per second
  • Set timebase, Obtain display.
  • One or more pulses per division or whole display?
  • DC or AC ??? Try it.
  • Volts per division. Vertical
  • Pulses per division. Horizontal
  • Measure volts, Length of pulse.
complex waves
Complex waves
  • AC ripple super imposed on a DC supply
  • Mixing two sine waves. Phase measurements. Lissajous patterns (X-Y)
  • Dual trace CROs
  • External Trigger ( Positive going and Negative going)
  • Noise
  • Frequency resolution of CROs.
read your operating manual
Read your operating manual
  • Read your operating manual
  • Read your operating manual
  • Enjoy reading your operating manual.
  • Test old projects, AM radios.
  • Audio or RF oscillators
  • Read your operating manual - ENJOY