Model: DSO 5202-P
Real Time sample rate: 1GSa/s
Display: Large (7.0-inch) color display
Innovative on screen HELP system
Sample Rate Range: 500MS/s--1GS/s
Record Length: 40K
FFT:Windows: Hanning, Flatop, Rectamgular, Bartlett, Blackman; 1024 sample point
Low Frequency Response (-3db):≤10Hz at BNC
Trigger mode: Auto, Normal, Single
Trigger type: Edge, Video, Pulse, Slope, Over time, Alternative
USB host and device connectivity, standard (note: USB port is NOT intended to be used to recharge cell phones or other usb charged devices.)
Multiple automatic measurements
Four math functions, including FFTs standard
Provides software for PC real-time analysis
The response characteristic of digital oscilloscope and its choose and buy skill
Another reason why high speed digital oscilloscope chooses brick wall reaction type is to avoid or minimize Aliasing phenomenon. When using digital oscilloscopes to measure high speed signals, graphics confusion can occur, mainly because some signals are mixed with unnecessary waveforms when reproducing the sampled high speed signals. These mixed signal frequency components can distort the original signal waveform and, in severe cases, cause measurement errors.
Most of the pattern confusion occurs in the analog to digital converter (adc) continuous signals, which contain components that exceed the Nyquist frequency, or half the sampling frequency.This component retraces in the Nyquist frequency domain and appears in the oscilloscope measurement bandwidth. It can be clearly seen from the frequency characteristic diagram that the figure confusion effect of the brick wall reactive oscilloscope is negligible.
Under the same conditions, it can be clearly seen that in the field beyond the Nyquist frequency of 2GHz, there is almost no signal, which can inhibit the occurrence of confusion.
In addition, if 20GHz, 10GHz and 5GHz sampling frequencies are used to measure waveforms with a period of 2.2ns and a rise time of about 90ps, different results will be obtained.The lower the sampling frequency is, the longer the actual measurement value of rising time is, and the waveform cannot be faithfully presented.
At present, the high-speed serial interface measurement USES the real-time sampling broadband digital oscilloscope, and the sampling frequency of the high performance machine equipped with the analog to digital converter is up to about 20GHz. Generally, in order to reduce the occurrence of graphics confusion, the sampling frequency of a gaussian reactive oscilloscope should be 4-6 times of the input signal, while that of a brick wall reactive oscilloscope only needs 2.5 times.
Generally, the frequency band is lower than 1GHz, so gaussian reaction system is mostly adopted, while the instruments higher than 1GHz are mostly brick wall reaction system.Table 2 shows the advantages and disadvantages of the two types of reactive oscilloscopes.
Choose oscilloscope according to performance requirement
So, how to choose the most suitable oscilloscope? There are four simple steps:
Calculate the highest frequency component fmax of the measured signal.The upper limit of the signal frequency component can be calculated by measuring the rising time of the signal.Assuming that the rise time is migrated from 20% to 80%, the approximate value can be estimated using the mathematical formula (0.4/ signal rise time) rather than directly from the data transmission rate.Take the popular third-generation bus PCIExpress, which in most cases has a rise time of about 100ps.
Select the response characteristics of the oscilloscope. That is to choose a suitable one between the gaussian reaction system and the brick wall reaction system.
The necessary input bandwidth must be secured. It is related to the measurement error of rise time. An instrument company has done simulation experiments: if the brick wall reactive system allows 3% error, the bandwidth can be calculated with (1.4 fmax); If the error is limited to 10%, use (1.2 fmax) to calculate. When the tolerance error is 20%, it is calculated by (1.0 fmax).
Estimate the lowest sampling frequency. This value takes advantage of the above bandwidth value, which is a minimum (2.5 bandwidth) for a brick wall reactive oscilloscope.
The above four points can be used to illustrate a case: the rise time of 100ps digital signal, its fmax is 4GHz, select the brick wall reaction oscilloscope, assuming that the error of the rise time is limited to 3%, then the bandwidth of the input signal is 5.6ghz, therefore, the minimum sampling frequency also needs 14GHz.
If the sampling frequency of 14GHz is applied to the gaussian reaction system, the input bandwidth becomes 3.5ghz, and the rising time of the measured signal is 220ps, which is half of the difference with the brick wall reaction system.Some wide-band real-time oscilloscopes rely on the active application of digital signal processing to realize the characteristics of brick wall reactive system.After all, circuit technology alone is unlikely to achieve desirable characteristics.
In a word, whether the bandwidth and sampling frequency are suitable or not is an important pointer when choosing expensive oscilloscope.In addition, understanding the characteristics of the test instrument is also the key to mastering the correct measurement.
Twelve tips of oscilloscope you must know
(1). The most valuable index of oscilloscope: Bandwidth, class parameter
(2). How high is the sampling rate?
Generally speaking, the sampling rate is 5 times the bandwidth, such as 200M oscilloscope, with 1G sampling rate is ok.
The pursuit of higher sampling rate is nothing more than to catch small burrs, but these high frequency burrs have been filtered out in the bandwidth layer, and higher sampling rate cannot bring good benefits.
(3) What is the difference between normal trigger and automatic trigger?
Normal trigger, it will sample the waveform only with trigger event satisfies the condition.
Automatic trigger, after wait for a moment, if there is no eligible trigger events occur, the oscilloscope will force the trigger function and start sampling. As random trigger position, the waveform will show unsteady. If above sequence occurs, please adopt normal mode.
(4) How to catch abnormal signal under uncertain condition?
You could catch the signal with template trigger.
When the template trigger is turned on, the template actually comes as a layer. It will constantly detect whether there is waveform that will touch the area of the template. When there is waveform that touches the template, a signal will be detected and it will be filtered and displayed.
(5) Are those channels isolated of oscilloscope?
No. Bottom of oscilloscope is connected with the earth, it could not be connected directly with the zero line.
To isolation, transformer could directly measure 220V city power, however, this is not recommended, and the safest and correct method it to use difference probes.
(6) Which is more accurate between oscilloscope and multimeter when measure voltage?
The vertical resolution ratio of general oscilloscopes is 8 bits. The measure accuracy is related to vertical resolution ratio and vertical gear.
The accuracy of multimeter is much higher. ADC of six and a half meter is up to 24 bits. That of handheld meter is far more than 8 bits. The voltage measured by the multimeter is more reliable.
(7) Differences between probe X1 and gear X10?
Two important points
Different attenuate bandwidth, signal x1 gear amplitude does not decay. X10 gear signal decay to 1/10 of original signal.
Different bandwidth, bandwidth of X1 gear is almost 10M, and 250M for X10 gear.
(8) Does the general oscilloscope probe need to be calibrated periodically?
The standard does not have a specific metering specification for the probe, but for passive probes, at least the probe compensation must be adjusted when the probe is replaced and the probe switches channels.
(9) What is main factor determines the price of oscilloscope probe ?
The main determinants of price are, of course, bandwidth and functionality.
There are many types of oscilloscope probe, different performance, such as high voltage, difference, active high-speed probe and so on, the price also from a few hundred yuan to nearly ten thousand dollars.
The probe is part of the oscilloscope contact circuit. A good probe can provide the fidelity required for testing.To do this, even passive probes must have a very large number of passive device compensation circuits (RC networks) inside.
(10) Is there any way to measure the working condition of high frequency transformer or inductor core by oscilloscope?
Can rely on the oscilloscope's own power analysis software to do, there is a function - B-H curve analysis, it can reflect the working state of the magnetic core, but also can measure the dynamic inductance value, and get the core loss.
(11) Can an oscilloscope perform Fourier decomposition?
Modern digital oscilloscope mostly has FFT function, but need to pay attention to FFT can analyze the number of points, which directly determines the accuracy of FFT analysis results, avoid spectrum leakage.ZDS2000 series oscilloscope is equipped with 4M point FFT analysis.
(12) Can oscilloscope filter? Such as low pass filtering of PWM wave?
Oscilloscopes typically have a 20MHz bandwidth limit, and this is a hardware filter.Some oscilloscopes also support software filters with adjustable cutoff frequencies.The ZDS2024Plus is adjustable from 100Hz to 100MHz.