Things to consider when choosing a Basic Oscilloscope
Basic oscilloscopes are used as windows into signals for troubleshooting circuits or checking signal quality. They generally go together with bandwidths from around fifty megahertz to two hundred megahertz and are found in nearly every design laboratory, education lab, service centre and manufacturing environment.
The digital storage oscilloscope
System bandwidth determines an oscilloscope’s ability to measure an analogue signal. Specifically, it determines the maximum frequency that the instrument can accurately measure. Bandwidth is also a key determining factor in price.
The probe and oscilloscope form a measurement system that has an overall bandwidth. Using a low-bandwidth probe will lower the overall bandwidth so be sure to use probes that are matched to the scope.
The sample rate of an oscilloscope is comparable to the frame rate of a motion-picture camera. It determines how much waveform detail the scope will capture.
The quicker you sample, the less information you’ll lose and the better the scope will represent the signal under test. But the faster you will fill up your memory, too, which limits the time you can capture.
Digital oscilloscopes sample analogue channels to store and display them. In general, the more channels the better, although adding channels adds to the price.
Some instruments share the sampling system between channels to save money. But beware: the number of channels you switch on will scale back the sample rate.
Good measurements begin at the probe tip. The scope and probe work together as a system, so be sure to consider probes when selecting an oscilloscope. During measurements probes actually become a part of the circuit, introducing resistive, capacitive, and inductive loading that alters the measurement. To minimise the effect it’s best to use probes that are designed for use with your scope. Select passive probes that have sufficient bandwidth. The probe’s bandwidth should match that of the oscilloscope.
A broad range of compatible probes will allow you to use your scope in more applications. Check to see what’s available for the scope before you buy.
The wider the variety of trigger choices obtainable the more versatile the scope (and the faster you get to the root reason for a problem!):
- Digital/pulse triggers: pulse width, runt pulse, rise/fall time, setup-and-hold
- Logic triggering
- Serial data triggers: embedded system designs use both serial (I2C, SPI,CAN/LIN…) and parallel buses.
- Video triggering
Record length is the total number of points during a complete waveform record. A scope can store only a restricted number of samples therefore, in general, the greater the record length the better.
A good basic scope can store over 2,000 points, which is quite enough for a stable sine-wave signal (needing maybe five hundred points). But to find the causes of timing anomalies in a complex digital data stream consider 1 Mpoints or more.
Zoom & Pan allows you to zoom in on an event of interest, and pan the area backwards and forwards in time. Search & Mark lets you search through the entire acquisition and automatically mark every occurrence of a user-specified event.
Oscilloscopes with record lengths in the millions of points can show many screens worth of signal activity, essential for examining complex waveforms.