How to choose digital oscilloscope?
How to choose oscilloscope reasonably as the price difference of oscilloscope nearly 50 times between low-grade with high-grade.
The relationship between the bandwidth selection and the highest signal frequency to be measured is needed if accurate measurements are required. Let’s check below example, there is one pulse signal with 50 MHZ, to ensure scope of signal and accuracy of rising delay, the bandwidth of oscilloscope should be 3-5 times of measured signal’s frequency and the accurate measurement should be 8-10 times or more.
Sine wave: as usual, need more than 5 sampling sites during one period as the waveform will be more close to the actual one with more sampling sites.
Pulse wave: rising delay should be more than 5 sampling sites.
Accurate measurement rising delay should be more than 10 sampling sites.
3. Record length: record length=sample*scanning speed*10, it could also be called waveform observation time.
4. Trigger function: ensure that the measured signal can be captured and synchronized to facilitate the observation and analysis of the measured waveform
Trigger methods: automatic trigger, normal trigger and single trigger
Two kinds of trigger function
1) Edge trigger: all digital oscilloscopes have this function, It refers to positive edge, negative edge trigger, window trigger, before trigger and after trigger.
2）Smart trigger：This is considered perfectly in high-grade oscilloscopes. currently there are: delay trigger, sequence trigger, burr trigger, interval trigger, leakage logic surface trigger, TV trigger, this trigger......
5. Analysis function: Should have very strong automatic processing, computation, test and analysis ability of signal
1）Shape and parameters pass/fail automatic test function
2) Advanced function processing: average, differential, polar, exponential, logarithm, power, square root, envelope, high score system, etc.
3）FFT spectrum operation function from 10k-4m point, with power spectrum, power density, phase vector, imaginary part, real part and other measurements;
4）The direct square analysis can be used for the stability calculation of the direct square test signal from 500 points to 8M points according to various parameters
5）Waveform parameter Trend analysis function, Jitter and time analysis;
6) Could open 2-8 windows to observe original waveform and processed waveform simultaneously.
X-Y display and X-Y+X-T and Y-T display are provided, can also carry on the vernier measurement makes it specially suitable for vector diagram analysis of digital communication signals.
6. Record and print signal
1) Can be stored in a test line on a floppy and hard disk, and can be read on a PC. Some digital oscilloscopes are equipped with built-in, convenient to print and analyze long time signal;
2) Some oscilloscopes also provide VGA interface.
Advantages and disadvantages of using digital oscilloscope
The development of oscilloscope probe
In the past 50 years, the interface design of various oscilloscope probes has been evolving continuously to meet the requirements of increased instrument bandwidth speed and measurement performance. In the earliest days, banana plugs and UHF connectors were commonly used. In the 1960s, the common BNC connector became the common probe interface type because BNC was smaller and more frequent. Currently, the BNC probe interface is still used for test and measurement instrument design, and the current higher quality BNC connector provides a maximum available bandwidth function of nearly 4GHz.
Later, some manufacturers put forward the common workarounds, BNC type probe interface design in the use of the BNC connector at the same time, additional provides a simulation code detection scale coefficients of stitching, as part of the mechanical and electrical interface design, which makes the oscilloscope is compatible with automatic detection and change the oscilloscope display of vertical attenuation range.
Requirements for oscilloscope current probe
Wide frequency range: from dc to tens or even hundreds of megabytes.
The range is large: from milliampere to kiloampere.
Small size: with the improvement of integration and the increase of signal frequency, the external size of components is getting smaller and shorter and pins are getting shorter and shorter.
Easy operation and high accuracy.