http://weelookang.blogspot.sg/2012/10/ejs-open-source-cathode-ray.html
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| http://weelookang.blogspot.sg/2015/06/ejss-cathode-ray-oscilloscope-cro.html EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model author: +Fu-Kwun Hwang and +Loo Kang Wee author of EJSS: +Francisco Esquembre Run: Link1 , Link2 Download and unzip: Link1, Link2 Source code: Link1 , Link2 |
http://www.doctronics.co.uk/scope.htm
http://www.doctronics.co.uk/scope.htm
Like a televison screen, the screen of an oscilloscope consists of a cathode ray tube. Although the size and shape are different, the operating principle is the same. Inside the tube is a vacuum. The electron beam emitted by the heated cathode at the rear end of the tube is accelerated and focused by one or more anodes, and strikes the front of the tube, producing a bright spot on the phosphorescent screen.
The electron beam is bent, or deflected, by voltages applied to two sets of plates fixed in the tube. The horizontal deflection plates, or X-plates produce side to side movement. As you can see, they are linked to a system block called the time base. This produces a sawtooth waveform. During the rising phase of the sawtooth, the spot is driven at a uniform rate from left to right across the front of the screen. During the falling phase, the electron beam returns rapidly from right ot left, but the spot is 'blanked out' so that nothing appears on the screen.
In this way, the time base generates the X-axis of the V/t graph.
Effects of t/div, which is 1/C
The slope of the rising phase varies with the frequency of the sawtooth and can be adjusted, using the TIME/DIV control, to change the scale of the X-axis. Dividing the oscilloscope screen into squares allows the horizontal scale to be expressed in seconds, milliseconds or microseconds per division (s/DIV, ms/DIV, µs/DIV). Alternatively, if the squares are 1 cm apart, the scale may be given as s/cm, ms/cm or µs/cm.
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| 1/C , effects of t/div = 0.5
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| 1/C , effects of t/div = 0.25
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| 1/C , effects of t/div = 0.125
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| 1/C , effects of t/div = 0.625
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
|
The signal to be displayed is connected to the input. The AC/DC switch is usually kept in the DC position (switch closed) so that there is a direct connection to the Y-amplifier. In the AC position (switch open) a capacitor is placed in the signal path. As will be explained in Chapter 5, the capacitor blocks DC signals but allows AC signals to pass.
effects of V/div
The Y-amplifier is linked in turn to a pair of Y-plates so that it provides the Y-axis of the the V/t graph. The overall gain of the Y-amplifier can be adjusted, using the VOLTS/DIV control, so that the resulting display is neither too small or too large, but fits the screen and can be seen clearly. The vertical scale is usually given in V/DIV or mV/DIV.
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| V/div, effects of V/div = 10
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| V/div, effects of V/div = 15
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| V/div, effects of V/div = 30
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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The trigger circuit is used to delay the time base waveform so that the same section of the input signal is displayed on the screen each time the spot moves across. The effect of this is to give a stable picture on the oscilloscope screen, making it easier to measure and interpret the signal.
Changing the scales of the X-axis and Y-axis allows many different signals to be displayed. Sometimes, it is also useful to be able to change the positions of the axes. This is possible using the X-POS and Y-POS controls. For example, with no signal applied, the normal trace is a straight line across the centre of the screen. Adjusting Y-POS allows the zero level on the Y-axis to be changed, moving the whole trace up or down on the screen to give an effective display of signals like pulse waveforms which do not alternate between positive and negative values.
The above information are quoted from http://www.doctronics.co.uk/scope.htm
This java applet shows the basic functions of an oscilloscope.
The oscilloscope is an electronic instrument widely used in making electrical measurements.
The main component of the oscilloscope is the cathode ray tube (CRT).
The CRT is a vacuum tube in which electrons are accelerated and deflected under the influence of electric field. The electrons are deflected in various directions by two sets of plate placed at right angle to each other in the neck of the tube.
Signal for the horizontal deflection plate (X-axis) is generated by the scope
It mathematical form is Fx(t)= C t + D (default)
C : time scale
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effects of C = 51, one complete period covers 10 divisions
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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effects of C =25.5, two complete period covers 10 divisions
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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effects of C = 12.75, four complete period covers 10 divisions
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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effects of C = 6.375, eight complete period covers 10 divisions
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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effects of C = 3.1875, sixteen complete period covers 10 divisions
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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D : horizontal offset
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| D , effects of X offset = 18
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| D , effects of X offset = 36
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
|
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| D , effects of X offset = 48
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
|
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| D , effects of X offset = 64
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
|
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| C , effects of X offset = 80
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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Effects of Y offset, V0
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| V0 , effects of Y offset = 18
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| V0, effects of Y offset = 36
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| V0, effects of Y offset = 54
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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Drag the mouse button to change values for Time/Div, Volt/Div , YOffset and XOffset.
The external signal (need to be measured) is applied to the vertical deflection plate (Y axis).
The default form for this java applet is Fy(t)=A sin(w t + B)
You can change X or Y axis signal to either kind of signal.
X = C t + D
X = A sin( w t + B)
Y = A sin(w t + B)+ V0 default mode Lissajou's figure
Y = C t + D not supported for an oscilloscope
These select the horizontal speed of the CRT's spot as it creates the trace; this process is commonly referred to as the sweep. In all but the least-costly modern oscilloscopes, the sweep speed is selectable and calibrated in units of time per major graticule division. Quite a wide range of sweep speeds is generally provided, from seconds to as fast as picoseconds (in the fastest) per division. Usually, a continuously-variable control (often a knob in front of the calibrated selector knob) offers uncalibrated speeds, typically slower than calibrated. This control provides a range somewhat greater than that of consecutive calibrated steps, making any speed available between the extremes.
The vertical position control moves the whole displayed trace up and down. It is used to set the no-input trace exactly on the center line of the graticule, but also permits offsetting vertically by a limited amount. With direct coupling, adjustment of this control can compensate for a limited DC component of an input.
X = A sin( w t + B)
Y = A sin(w t + B)+ V0 default mode Lissajou's figure
effects of A: amplitude of wave signal detected
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| effects of A = 18, since v/div is 18, it has the height of 1 division.
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| effects of A = 36, since v/div is 18, it has the height of 2 divisions.
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| effects of A = 54, since v/div is 18, it has the height of 3 divisions.
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| effects of A = 72, since v/div is 18, it has the height of 4 divisions.
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
|
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| effects of A = 90, since v/div is 18, it has the height of 5 divisions.
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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effects of w: wavelength of wave signal detected
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| effects of w = 1.5707 = 2π/16, where T = 16. 4 periods inside one division. note that B = 0 for simplicity of wave
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| effects of w = 0.7853 = 2π/16, where T = 16. 2 periods inside one division
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| effects of w = 0.3926 = 2π/16, where T = 16. 1 period inside one division
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| effects of w = 0.1963 = 2π/16, where T = 16. 0.5 periods inside one division
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| effects of w = 0.0982 = 2π/16, where T = 16. 1 period inside 4 divisions or 0.25 period inside 1 division
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| effects of w = 0.0491 = 2π/16, where T = 16. 1 period inside 8 divisions or 0.125 period inside 1 division
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| effects of w = 0.0393= 2π/16, where T = 16. 1 period inside 10 divisions or 0.1 period inside 1 division
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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effects of B: phase difference detected in degrees
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| effects of B = 90 degree. phase difference =B
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
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| effects of B = 180 degree. phase difference =B
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
|
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| effects of B = 270 degree. phase difference =B
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
|
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| effects of B = 360 degree = 0 degree. phase difference =B
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
|
effects of D: Xoffset of wave signal detected
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D , effects of X offset = 16
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
|
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D , effects of X offset = 32
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
|
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D , effects of X offset = 48
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
|
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D , effects of X offset = 64
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
|
 |
D , effects of X offset = 80
EJSS Cathode Ray Oscilloscope CRO JavaScript Applet Model
author: +Fu-Kwun Hwang and +Loo Kang Wee
author of EJSS: +Francisco Esquembre
|
Y = C t + D not supported for an oscilloscope
Creative Commons Attribution Animated Gifs
https://en.wikipedia.org/wiki/OscilloscopeTimebase controls
Vertical position control
Horizontal position control
Dual-trace controls
Each input channel usually has its own set of sensitivity, coupling, and position controls, although some four-trace oscilloscopes have only minimal controls for their third and fourth channels.
Dual-trace oscilloscopes have a mode switch to select either channel alone, both channels, or (in some) an X‑Y display, which uses the second channel for X deflection. When both channels are displayed, the type of channel switching can be selected on some oscilloscopes; on others, the type depends upon timebase setting. If manually selectable, channel switching can be free-running (asynchronous), or between consecutive sweeps. Some Philips dual-trace analog oscilloscopes had a fast analog multiplier, and provided a display of the product of the input channels.
Multiple-trace oscilloscopes have a switch for each channel to enable or disable display of that trace's signal.
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