Digital storage oscilloscope
Encyclopedia
A digital storage oscilloscope is an oscilloscope
which stores and analyses the signal digitally
rather than using analogue
techniques. It is now the most common type of oscilloscope in use because of the advanced trigger, storage, display and measurement features which they typically provide.
The input analogue signal is sampled and then converted into a digital record of the amplitude of the signal at each sample time. The sampling frequency should be the Nyquist rate
or better to avoid aliasing
. These digital values are then turned back into an analogue signal for the display if this is a cathode ray tube
(CRT) or otherwise transformed as needed for the various possible types of output — liquid crystal display
, chart recorder
, plotter
or network interface
.
Digital storage oscilloscopes are usually large and expensive $400 USD or more. However, small, pocket-size models are now available which, though limited in function, may retail for as little as $50 USD.
, root mean square
(RMS) and frequencies. They may be used to capture transient signals
when operated in a single sweep mode — something that was normally difficult to achieve with an analogue oscilloscope.
Oscilloscope
An oscilloscope is a type of electronic test instrument that allows observation of constantly varying signal voltages, usually as a two-dimensional graph of one or more electrical potential differences using the vertical or 'Y' axis, plotted as a function of time,...
which stores and analyses the signal digitally
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
rather than using analogue
Analog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
techniques. It is now the most common type of oscilloscope in use because of the advanced trigger, storage, display and measurement features which they typically provide.
The input analogue signal is sampled and then converted into a digital record of the amplitude of the signal at each sample time. The sampling frequency should be the Nyquist rate
Nyquist rate
In signal processing, the Nyquist rate, named after Harry Nyquist, is two times the bandwidth of a bandlimited signal or a bandlimited channel...
or better to avoid aliasing
Aliasing
In signal processing and related disciplines, aliasing refers to an effect that causes different signals to become indistinguishable when sampled...
. These digital values are then turned back into an analogue signal for the display if this is a cathode ray tube
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
(CRT) or otherwise transformed as needed for the various possible types of output — liquid crystal display
Liquid crystal display
A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....
, chart recorder
Chart recorder
A chart recorder is an electromechanical device that records an electrical or mechanical input trend onto a piece of paper . Chart recorders may record several inputs using different color pens and may record onto strip charts or circular charts...
, plotter
Plotter
A plotter is a computer printing device for printing vector graphics. In the past, plotters were widely used in applications such as computer-aided design, though they have generally been replaced with wide-format conventional printers...
or network interface
Network interface
Network interface may refer to:* Network interface controller, the device a computer uses to connect to a computer network* Network interface device, a demarcation point for a telephone network...
.
Digital storage oscilloscopes are usually large and expensive $400 USD or more. However, small, pocket-size models are now available which, though limited in function, may retail for as little as $50 USD.
Advantages
Digital oscilloscopes will usually analyse and provide values as well as visual displays. These values will typically include averages, minima, maximaMaxima
Maxima is a computer algebra system based on a 1982 version of Macsyma. It is written in Common Lisp and runs on all POSIX platforms such as Mac OS X, Unix, BSD, and GNU/Linux as well as under Microsoft Windows...
, root mean square
Root mean square
In mathematics, the root mean square , also known as the quadratic mean, is a statistical measure of the magnitude of a varying quantity. It is especially useful when variates are positive and negative, e.g., sinusoids...
(RMS) and frequencies. They may be used to capture transient signals
Transient (oscillation)
A transient event is a short-lived burst of energy in a system caused by a sudden change of state.The source of the transient energy may be an internal event or a nearby event...
when operated in a single sweep mode — something that was normally difficult to achieve with an analogue oscilloscope.
Further reading
- Hickman, Ian (1997.) "Digital storage oscilloscopes." Newnes. ISBN 0-7506-2856-1
External links
Resources (White papers, technical papers, application notes)
- The Effective Number of Bits (ENOB) - This application note explains how to measure the oscilloscope ENOB.
- The Impact of Digital Oscilloscope Blind Time on Your Measurements - This application note explains the background of blind time and points out why a high acquisition rate is important.