PC-based oscilloscopes Oscilloscope types

a pc-based oscilloscope new type of oscilloscope emerging consists of specialized signal acquisition board (which can external usb or parallel port device, or internal add-on pci or isa card). hardware consists of electrical interface providing isolation , automatic gain controls, several high-speed analog-to-digital converters , buffer memory, or on-board digital signal processor (dsps). depending on exact hardware configuration, hardware best described digitizer, data logger or part of specialized automatic control system.

the pc provides display, control interface, disc storage, networking , electrical power acquisition hardware. viability of pc-based oscilloscopes depends on current widespread use , low cost of standardized pcs. since prices can range little us$100 as us$10,500 depending on capabilities, such instruments particularly suitable educational market, pcs commonplace equipment budgets low.

pco acquisition hardware, in cases, may consist of standard sound card or game port, if audio , low-frequency signals involved, though in many cases considerably more robust. pco can transfer data computer in 2 main ways — streaming, , block mode. in streaming mode data transferred pc in continuous flow without loss of data. way in pco connected pc (e.g., ieee1394, ethernet, usb etc.) dictate maximum achievable speed , thereby frequency , resolution using method. block mode utilizes on-board memory of pco collect block of data transferred pc after block has been recorded. pco hardware resets , records block of data. process happens quickly, time taken vary according size of block of data , speed @ can transferred. method enables higher sampling speed, in many cases hardware not record data whilst transferring existing block, meaning data loss occur.

the advantages of pc-based oscilloscopes include:

lower cost stand-alone oscilloscope, assuming user owns pc. professional-grade pco hardware (with bandwidth in mhz rather in khz range) tends more expensive typical pci sound card, , can cost more new pc (pco-chart).
easy exporting of data standard pc software such spreadsheets , word processors. or power tools numerical analysis software , tailored software.
ability control instrument running custom program on pc , thereby automate tests etc. or simple control setup remote location.
use of pc s networking , disc storage functions, cost lot when added self-contained oscilloscope.
pcs typically have large high-resolution color displays can easier read smaller displays found on conventional oscilloscopes. color can utilized differentiate waveforms. can show increased information including more of waveform or extras automatic waveform measurements , simultaneous alternative views.
portability when used laptop pc.
some smaller physically handheld oscilloscopes.

there disadvantages, include:

power-supply , electromagnetic noise pc circuits, requires careful , extensive shielding obtain low-level signal resolution.
data transfer rates pc, dependent upon connection method. affects maximum sampling rate , resolution achievable pco when streaming.
need owner install oscilloscope software on pc, may not compatible current release of pc operating system.
time pc boot, compared instant start-up of self-contained oscilloscope (although, modern oscilloscopes pcs or similar machines in disguise, distinction narrowing).

as more processing power , data storage included in oscilloscopes, distinction becoming blurred. mainstream oscilloscope vendors manufacture large-screen, pc-based oscilloscopes, fast (multi-ghz) input digitizers , highly customized user interfaces.

software pc may use sound card or game port acquire analog signals, instead of dedicated signal acquisition hardware. however, these devices have restricted input voltage ranges, limited precision/resolution, , restricted frequency ranges. ground reference these inputs same ground pc logic , power supply; may inject unacceptable amounts of noise circuit under test. however, these devices can useful demonstration, hobby use, or specific setups these factors won t interfere. ground reference can eliminated capacitor ac coupling or signal transformer.

if sound card used, frequency response limited audio range, , dc signals cannot measured without hardware modification. number of inputs limited number of recording channels , inputs can handle audio line-level voltages (usually ~1 vpp) without risk of damage.

if game port used acquisition hardware, possible sampling frequency low, typically below 1 khz, , input voltages can vary on range of couple of volts. in addition, game port cannot programmed specific sampling rate, nor can assigned precise quantization step. analog digital conversion accomplished triggering discharge of capacitor , measuring how long takes charge fixed threshold seen 0 1 transition on pc isa bus. means huge resistance @ input takes longer measure low resistance, results in asymmetrical sampling intervals. these limitations make suitable low-precision visualization of low frequency signals.