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Analog & digital oscilloscope

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Asir Foysal
Asir Foysal

The oscilloscope is the most powerful instrument in our arsenal of electronic instruments. It is widely used for measurement of time-varying signals. Any time you have a signal that varies with time - slowly or quickly - you can use an oscilloscope to measure it - to look at it, and to find any unexpected features in it.

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Analog & Digital Oscilloscope ICE 251 (Electronic Circuit) Assignment SUBMITTED BY SUBMITTED TO ASIR FOYSAL SHAKIB MD.ARIF IFTEKHER asirfoysal@gmail.com
1 Oscilloscope The oscilloscope is the most powerful instrument in our arsenal of electronic instruments. It is widely used for measurement of time- varying signals. Any time you have a signal that varies with time - slowly or quickly - you can use an oscilloscope to measure it - to look at it, and to find any unexpected features in it. There are various types and models available. But we discuss here about two types of Oscilloscope. Analog and Digital oscilloscope. Analog Oscilloscope In analog technology, a wave is recorded or used in its original form. Analog oscilloscope uses the cathode ray tube (CRT). This form of display was for many years the only viable form of display that could be used to display images. Accordinglyit was used in television sets for many years, although other forms of display including LCDs, LEDs and many other format are now used, but these all require digital signal inputs to the display. Works: The analogue scope uses the cathode ray tube to display signals in both X (horizontal) and Y (vertical) axes. Typically the Y axis is the instantaneous value of the incoming voltage and the X axis is ramp waveform. As the ramp waveform increases in voltage so the trace moves across the screen in a horizontal direction. When it reaches the end of the screen, the waveform returns to zero and the trace moves backto the beginning. Advantages: Analog scopes are generally much less expensive than their digital counterparts. Thetechnologyis well established and is therefore less expensive than leading edge technologies where large
2 levels of development costs have to be recovered in addition to the component and production costs being higher Analog oscilloscopes are able to provide a good level of performance that is more than adequate for many laboratory and service situations. It is often found that analog oscilloscopes may be available in an equipment store when all the other digital scopes are in use. Provided that their performance is satisfactory, theanalogue option may provide an ideal way forwards. Digital Oscilloscope Most electronics engineers will have used an analog scope at some time and will be familiar with its layout and operation. In fact, many people purchasing oscilloscopes todayare replacing analog with digital. Modern DSOs, with their PC connectivity, can also be fully integrated into Automatic Test Equipment (ATE) systems. In addition, the DSO is often used as the front–end of a high speed data acquisition system, making the cost per channel much more economically viable. Work: The vertical input is digitized by an analog to digital converter to create a data set that is stored in the memory of a microprocessor. The data set is processed and then sent to the display, which in early DSOs was a cathode ray tube, but is now more likely to be an LCD flat panel. DSOs with color LCD displays are common. Thedata set can be sent over a LAN or a WAN for processing or archiving. The screen image can be directly recorded on paper by means of an attached printer or plotter, without the need for an oscilloscope camera. The oscilloscope's own signal analysis software can extract many useful time-domain features (e.g., rise time, pulse width, amplitude), frequencyspectra, histograms and statistics, persistence maps, and a large number of parameters meaningfulto engineers in specialized
3 fields such as telecommunications, disk drive analysis and power electronics. Advantages: Brighter and bigger display with color to distinguish multiple traces. Equivalent time sampling and averaging across consecutive samples or scans lead to higher resolution down to µV Peak detection Easy pan and zoom across multiple stored traces allows beginners to work without a trigger This needs a fast reaction of the display (some oscilloscopes have 1 ms delay) The knobs have to be large and turn smoothly Also slow traces like the temperature variation across a day can be recorded Allows for automation. ANALOG VS DIGITAL OSCILLOSCOPES With analog scopes life was simple: You just selected the bandwidth that you required. For digital scopes, sampling rate and memory depth are equally important. For DSOs, the sampling rate is usually specified in mega samples per second (MS/s) or giga samples per second (GS/s). The Nyquist criterion states that the sampling rate must be at least twice the maximum frequencythat you want to measure: for a spectrum analyzer this may be true, but for a scope you require at least Why a digital oscilloscope? The first feature to consider is bandwidth. This can be defined as the maximum frequencyof signal that can pass through the front–end amplifiers. It therefore follows that the analogue bandwidth of your
4 scope must be higher than the maximum frequencythat you wish to measure (real time).It is worth noting that most scope manufacturers define the bandwidth as the frequencyat which a sine wave input signal will be attenuated to 71% of its true amplitude (-3 dB point). Or, to put it another way, they allow the displayed trace to be 29% in error of the input before calling it a day. 5 samples to accuratelyreconstruct a waveform. Most scopes have two different sampling rates (modes) depending on the signal being measured: real–time and equivalent–time sampling (ETS) – often called repetitive sampling. However, ETS only works if the signal you are measuring is stable and repetitive, since this mode works by building up the waveform from successive acquisitions.

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Analog & digital oscilloscope

  • 1. Analog & Digital Oscilloscope ICE 251 (Electronic Circuit) Assignment SUBMITTED BY SUBMITTED TO ASIR FOYSAL SHAKIB MD.ARIF IFTEKHER asirfoysal@gmail.com
  • 2. 1 Oscilloscope The oscilloscope is the most powerful instrument in our arsenal of electronic instruments. It is widely used for measurement of time- varying signals. Any time you have a signal that varies with time - slowly or quickly - you can use an oscilloscope to measure it - to look at it, and to find any unexpected features in it. There are various types and models available. But we discuss here about two types of Oscilloscope. Analog and Digital oscilloscope. Analog Oscilloscope In analog technology, a wave is recorded or used in its original form. Analog oscilloscope uses the cathode ray tube (CRT). This form of display was for many years the only viable form of display that could be used to display images. Accordinglyit was used in television sets for many years, although other forms of display including LCDs, LEDs and many other format are now used, but these all require digital signal inputs to the display. Works: The analogue scope uses the cathode ray tube to display signals in both X (horizontal) and Y (vertical) axes. Typically the Y axis is the instantaneous value of the incoming voltage and the X axis is ramp waveform. As the ramp waveform increases in voltage so the trace moves across the screen in a horizontal direction. When it reaches the end of the screen, the waveform returns to zero and the trace moves backto the beginning. Advantages: Analog scopes are generally much less expensive than their digital counterparts. Thetechnologyis well established and is therefore less expensive than leading edge technologies where large
  • 3. 2 levels of development costs have to be recovered in addition to the component and production costs being higher Analog oscilloscopes are able to provide a good level of performance that is more than adequate for many laboratory and service situations. It is often found that analog oscilloscopes may be available in an equipment store when all the other digital scopes are in use. Provided that their performance is satisfactory, theanalogue option may provide an ideal way forwards. Digital Oscilloscope Most electronics engineers will have used an analog scope at some time and will be familiar with its layout and operation. In fact, many people purchasing oscilloscopes todayare replacing analog with digital. Modern DSOs, with their PC connectivity, can also be fully integrated into Automatic Test Equipment (ATE) systems. In addition, the DSO is often used as the front–end of a high speed data acquisition system, making the cost per channel much more economically viable. Work: The vertical input is digitized by an analog to digital converter to create a data set that is stored in the memory of a microprocessor. The data set is processed and then sent to the display, which in early DSOs was a cathode ray tube, but is now more likely to be an LCD flat panel. DSOs with color LCD displays are common. Thedata set can be sent over a LAN or a WAN for processing or archiving. The screen image can be directly recorded on paper by means of an attached printer or plotter, without the need for an oscilloscope camera. The oscilloscope's own signal analysis software can extract many useful time-domain features (e.g., rise time, pulse width, amplitude), frequencyspectra, histograms and statistics, persistence maps, and a large number of parameters meaningfulto engineers in specialized
  • 4. 3 fields such as telecommunications, disk drive analysis and power electronics. Advantages: Brighter and bigger display with color to distinguish multiple traces. Equivalent time sampling and averaging across consecutive samples or scans lead to higher resolution down to µV Peak detection Easy pan and zoom across multiple stored traces allows beginners to work without a trigger This needs a fast reaction of the display (some oscilloscopes have 1 ms delay) The knobs have to be large and turn smoothly Also slow traces like the temperature variation across a day can be recorded Allows for automation. ANALOG VS DIGITAL OSCILLOSCOPES With analog scopes life was simple: You just selected the bandwidth that you required. For digital scopes, sampling rate and memory depth are equally important. For DSOs, the sampling rate is usually specified in mega samples per second (MS/s) or giga samples per second (GS/s). The Nyquist criterion states that the sampling rate must be at least twice the maximum frequencythat you want to measure: for a spectrum analyzer this may be true, but for a scope you require at least Why a digital oscilloscope? The first feature to consider is bandwidth. This can be defined as the maximum frequencyof signal that can pass through the front–end amplifiers. It therefore follows that the analogue bandwidth of your
  • 5. 4 scope must be higher than the maximum frequencythat you wish to measure (real time).It is worth noting that most scope manufacturers define the bandwidth as the frequencyat which a sine wave input signal will be attenuated to 71% of its true amplitude (-3 dB point). Or, to put it another way, they allow the displayed trace to be 29% in error of the input before calling it a day. 5 samples to accuratelyreconstruct a waveform. Most scopes have two different sampling rates (modes) depending on the signal being measured: real–time and equivalent–time sampling (ETS) – often called repetitive sampling. However, ETS only works if the signal you are measuring is stable and repetitive, since this mode works by building up the waveform from successive acquisitions.
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