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.
Analog technique that determines the performance height of an oscilloscope
Although the oscilloscope is not instrument on the top of the hardware requirements, given the oscilloscope is the most familiar with many engineers is one of the biggest single instrument of test equipment market segment, so we interviewed in the world to do the oscilloscope bandwidth GHz level several representative, from the analysis on the oscilloscope hardware, with everyone together to understand the core of the oscilloscope design unit.
Bandwidth, sampling rate and storage depth, is the most intuitive decision an oscilloscope market value of the three features, including bandwidth can reflect the performance of the oscilloscope is the most obvious indicators, sampling rate values and bandwidth have been linked, while the two numerical oscilloscope is directly related to the final price, its value is basic it is decided by simulation unit of hardware performance.
The suspension ability of oscilloscope and the isolation ability between channels
For economical fault search application, usually need is double-channel oscillograph, however, the relationship of the requirements to observe several analog signals, will need a 4 channel oscilloscope, a lot of work in analog and digital two kinds of signal systems engineers can choose mixed signal oscilloscope (the oledata.mso), it will be logic analyzer channel count and triggered abilities associated with the comprehensive to have higher resolution time of oscilloscope display in a single instrument. If you measure three-phase electricity, thyristor and other active devices or lines, there is no absolute zero between the two ends, that is, the so-called floating signal, at this time from the safety and accuracy of operation, you should choose the isolated channel oscilloscope;If the timing and phase shift of multiple channels are compared, oscilloscopes with more than two channels should be selected, when the isolation between channels is more important.