Common problems encountered during the use of an oscilloscope

1. How to measure DC voltage?

A: First, you need to set the coupling mode to DC, adjust the vertical gear to a suitable value according to the approximate range, and then compare the displacement of the offset line with the channel mark.

2. When measuring 220V mains, the amplitude is beyond the screen range? How is the phase difference of the three-phase power supply measured?

Answer: The maximum input peak-to-peak voltage of the DS5000 series is 400V. According to the effective value, the peak-to-peak formula 220V is over 400V peak-to-peak, and the amplitude is beyond the normal range of the screen. When measuring the phase shift of the three-phase power supply with an oscilloscope, you can set the trigger source to be the mains, and use one channel to measure the AB waveform first, then store it as the reference waveform, and then connect the BC with the probe. At this time, the phase shift can be measured.

3. What is the inhibition of confusion?

A: Confusion refers to a situation in which the frequency acquired by the oscilloscope is less than 2 times the maximum frequency of the actual signal. Confusion suppression is specifically designed to prevent confusion, and the confusion suppresses the maximum frequency of the identifiable signal and acquires the signal at twice the maximum frequency.

4. How to capture non-periodic signals?

Answer: 1. Set the trigger level to the desired value. 2. Click the main control button SINGLE, the machine starts to wait. If a certain signal reaches the set trigger level, it will be sampled once and displayed on the screen. With this function, you can easily capture accidental events, such as a large burst of sudden glitch: set the trigger level just above the normal signal level, click the SINGLE button, the machine automatically triggers when the glitch occurs Record the waveform for a period of time before and after the trigger. Drag the trigger position marker line to get negative delay triggers of different lengths, which is convenient for observing the waveform before the glitch occurs.

5. How to observe the noise of low voltage DC power supply?

Answer: 1. Connect the oscilloscope probe between channel A1 (or A2) and the measured point. 2. Set the Trigger Source to A1 or A2 (must be the same as the channel input by the actual signal under test). 3. Click the A1 or A2 button and select the coupling mode as AC (AC) coupling. 4. Adjust the sampling rate and vertical sensitivity until a satisfactory display is obtained.

6. What is the application method of the DS5000 oscilloscope?

A: Please observe the real-time sampling mode for observing single signal. Observe the equivalent sampling method for observing high-frequency periodic signals. It is desirable to observe the envelope of the signal to avoid confusion. Please use the peak detection method. It is desirable to reduce the random noise in the displayed signal. Please use the average sampling method. The average number of times can be selected. Observe the low frequency signal and select the scroll mode mode. I want to display the waveform close to the analog oscilloscope effect, please choose the analog acquisition method.

7. What is the relationship between triggering and waveform acquisition?

A: For different types of oscilloscopes, the oscilloscope has different capture modes, and the relationship between trigger and waveform acquisition is different. In the case of an equivalent time sampling mode of a sampling oscilloscope or a real-time oscilloscope, the acquisition of one waveform requires multiple triggers. For the real-time sampling mode of the real-time oscilloscope, once triggered, the waveform will certainly be acquired once, without triggering, the waveform may also be acquired, which is the AUTO mode of the trigger. (There are three trigger modes, one is AUTO, no trigger, the waveform will be refreshed, but the waveform will be unstable on the screen, the other is NORMAL, only the trigger will refresh, the last one is SINGLE, the first trigger capture The waveform is not captured in the future.)

8. Can the RIGOL product automatically generate an EXCEL table after saving the waveform?

A: Yes. Ultrascope software can automatically save the downloaded waveform data to the file format of the Excel table. RVO virtual instrument does not automatically generate Excel table function in the software, but we provide a conversion tool (free download in the official homepage of RIGOL, software name: DatKit for RVO3000 & 4000 Series). Use this tool to save RVO as a text file format of "*.dat" file format converted to "*.txt", and modify txt to xls to save the data on the Excel sheet.

9. After the signal is acquired, the waveform of the signal does not appear in the picture. How to deal with it?

A: You can check the processing according to the following steps: 1. Check if the probe is properly connected to the signal cable; 2. Check if the signal cable is properly connected to the BNC (ie channel connector); 3. Check whether the probe and the object to be tested Normal connection; 4. Check if the signal is generated by the test object (the signal generated channel can be connected with the problematic channel to determine the problem). 5. Re-acquire the signal again.

10. What are the applications for glitch/pulse width triggering?

A: There are two typical applications for glitch/pulse width triggering. One is synchronous circuit behavior, such as using it to synchronize serial signals, or for applications with very severe interference, it is impossible to trigger the correct sync signal with edges. Pulse width trigger is One option; the other is to find anomalies in the signal, such as narrow glitch caused by interference or competition. Since the anomaly is occasional, it must be captured with a glitch trigger (another method is peak detection, but the peak value The method of detection may be limited by its maximum sampling rate, and at the same time, it can generally be seen and cannot be measured). If the pulse width of the measured object is 50 ns, and the signal has no problem, that is, there is no signal distortion or narrower caused by interference, competition, etc., the edge can be synchronized to trigger the signal without using glitch triggering. .

11. When choosing an oscilloscope, the most common consideration is bandwidth. Under what circumstances should you consider the sampling rate?

A: Depending on the object being tested, the minimum sampling interval (the reciprocal of the sampling rate) is expected to capture the signal details you need, provided the bandwidth is met. There are some empirical formulas about sampling rate in the industry, but basically they are all derived from the oscilloscope bandwidth. In practical applications, it is better not to use an oscilloscope to measure signals of the same frequency. If you are selecting, for sine wave, choose the oscilloscope bandwidth is 3 times the frequency of the measured sinusoidal signal. Above, the sampling rate is 4 to 5 times of the bandwidth, which is actually 12 to 15 times of the signal. If other waveforms, Ensure that the sample rate is sufficient to capture signal details. If you are using an oscilloscope, you can verify that the sampling rate is sufficient by: Stopping the waveform, amplifying the waveform, and if the waveform is changed (such as some amplitude), the sampling rate is not enough, otherwise it does not matter. It can also be analyzed by point display, and the sampling rate is enough.

12. How to eliminate burrs when using an oscilloscope?

A: If the glitch is inherent to the signal itself and you want to synchronize the signal (such as a sinusoidal signal) with an edge trigger, you can use the high frequency suppression trigger mode, which is usually synchronized. If the signal itself has a glitch, but you want the oscilloscope to take care of the glitch and not display glitch, it is usually difficult to do. You can try to use a method that limits bandwidth, but you may also be careful about the signal itself. If you use a logic analysis instrument, in general, using the state acquisition method, some of the glitch collected in the timed mode will not be visible.

13, DS5000 oscilloscope edge trigger, pulse width trigger and video trigger are suitable for measuring that kind of signal?

A: Edge trigger, you can set the trigger level, rising edge or falling edge. Edge triggering is also known as basic triggering. The pulse width trigger determines the trigger time based on the pulse width. Anomalous pulses can be captured by setting pulse width conditions. Video triggering can be triggered on the field or line of an NTSC, PAL or SECAM standard video signal.

14. Using the DS5000 series oscilloscope, how can I capture and save a random random signal and then re-analyze it?

A: If the so-called random signal is a single signal, then just set the vertical and horizontal scales that match the signal, adjust the trigger level, use the single-shot wait signal, and then use the storage type of STORAGE. The waveform save function can store the captured waveform, and the saved waveform needs to be re-displayed, and the waveform can be recalled to re-analyze the analysis.

15. Why is the waveform storage already stored settings, and what is the use of the storage settings?

A: First of all, the main difference between the two is that the storage space occupied by the waveform storage is much larger than the storage space. Therefore, considering the space and cost of the memory, you need to save the two separately. Second, there are differences in the recall of the two. The waveform is called out and the oscilloscope is in the STOP state. When the setting is called, the saved running state is not changed, and the waveform can be directly observed.

16. Each oscilloscope has a frequency range, such as 10M, 60M, 100M. . The oscilloscope I used at hand is nominally 60MHz. Can it be understood that it can measure up to 60MHz? But when I use it to measure the square wave of 4.1943MHz, I can't measure it. What is the reason?

A: A 60MHz bandwidth oscilloscope does not mean that a 60MHz signal can be measured very well. According to the oscilloscope bandwidth definition, if you input a 60MHz sine wave with a peak-to-peak value of 1V to a 60MHz bandwidth oscilloscope, you will see a 0.707V signal (30% amplitude measurement error) on the oscilloscope. If testing a square wave, the reference standard for the oscilloscope should be the signal rise time, oscilloscope bandwidth = 0.35 / signal rise time & TImes; 3, at this time your rise time measurement error is about 5.4%.

The probe bandwidth of the oscilloscope is also important. If the oscilloscope probe used, including its front-end accessory, has a very low system bandwidth, the oscilloscope bandwidth will be greatly reduced. If you use a 20MHz bandwidth probe, the maximum bandwidth that can be achieved is 20MHz. If the connecting wire is used at the front end of the probe, the performance of the probe will be further reduced, but it should not have much influence on the square wave around 4MHz, because the speed is not very fast.

Also look at the oscilloscope manual, some 60MHz oscilloscopes in the 1:1 setting, the actual bandwidth will be sharply reduced to below 6MHz, for the square wave around 4MHz, the third harmonic is 12MHz, the fifth harmonic is 20MHz If the bandwidth is reduced to 6MHz, the amplitude of the signal is greatly attenuated. Even if the signal can be seen, it is definitely not a square wave, but a sine wave whose amplitude is attenuated.

Of course, there are many reasons why the signal can not be measured. If the probe is not in good contact (this phenomenon is easy to eliminate), it is recommended to connect a function generator with a BNC cable to verify that the oscilloscope has any problems and that the probe has no problem. If you have any questions, you can contact the manufacturer directly.

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