Oscilloscope usage methods and techniques

How to use an oscilloscope

1. Obtaining a baseline: When the operator uses an oscilloscope without an instruction manual, he must first obtain a thin horizontal baseline before using the probe to perform other measurements. The specific method is as follows: (1) Preset the switches and knobs on the panel. Set the brightness to a moderate level, the focus and auxiliary focus to a moderate level, the vertical input coupling to "AC", the vertical voltage range selection to "5mv/div", the vertical working mode selection to "CH1", the vertical sensitivity fine-tuning calibration position to "CAL", the vertical channel synchronization source selection to the middle position, the vertical position to the middle position, the A and B scan time factors are preset at "0.5ms/div", the A scan time fine-tuning calibration position to "CAL", the horizontal displacement to the middle position, the scan working mode to "A", the trigger synchronization mode to "AUTO", the slope switch to "+", the trigger coupling switch to "AC", and the trigger source selection to "INT". (2) Press the power switch and the power indicator lights up. (3) Adjust the A brightness focus and other related control knobs to produce a thin and bright scan baseline. Adjust the baseline so that its position is in the middle of the screen and basically coincides with the horizontal coordinate scale. (4) Adjust the track parallelism control so that the baseline is parallel to the horizontal coordinate.

2. Display signal: In general, the oscilloscope itself has a 0.5Vp-p standard square wave signal output port. After obtaining the baseline, the probe can be connected here. At this time, there should be a series of square wave signals on the screen. Adjust the voltage range and scan time factor knobs, and the amplitude and width of the square wave should change. This shows that the oscilloscope has been basically adjusted and can be put into use.

3. Measure the signal: Connect the test line to the CH1 or CH2 input socket, and touch the test probe to the test point, and then you can observe the waveform on the oscilloscope. If the waveform amplitude is too large or too small, you can adjust the voltage range knob; if the waveform cycle display is not suitable, you can adjust the scanning speed knob.

Special usage method 1. AC peak voltage measurement (1) Obtain the baseline. (2) Adjust the V/div knob so that the waveform displays 5 div (i.e. 5 grids) in the vertical direction. (3) Adjust the "A trigger level" to obtain a stable display. (4) Use the following formula to calculate the peak voltage. Voltage (p-p): vertical deflection amplitude/degree x (VOLTS/div)/switch level x probe attenuation factor. For example: the measured upper peak to lower peak deflection is 5.6 degrees, the VOLTS/dir switch is set to 0.5, and the probe attenuation factor is x10, substitute the data into: voltage = 5.6X0.5X10 = 28 V. 2. Rise time measurement Rise time: horizontal distance (degrees) x time/degree (level)/expansion factor. For example: the distance between two points of the waveform is 5 degrees, the time/degree level is 1Us, and the x10 expansion is not expanded (i.e. x1), substitute the given value into: rise time I division; 5X1 / 1; 51xs. 3. Phase difference measurement Phase difference: horizontal difference (degrees) x horizontal scale calibration value (degrees/degrees). For example: the horizontal difference is 0.6 degrees, and each degree is calibrated to 45 degrees. Substitute the given value into the formula: Phase difference: 0.6x45:27

Tips for using an oscilloscope

1. How to measure DC voltage ?

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

2. Users reported that the amplitude exceeded the screen range when measuring 220V AC power? How to measure the phase difference of three-phase power ?

A: The maximum input peak-to-peak voltage of the DS5000 series is 400V. According to the formula for converting the peak-to-peak value from the effective value, the 220V AC power exceeds the 400V peak-to-peak value. It is normal that the amplitude exceeds the screen range. When using an oscilloscope to measure the phase shift of a three-phase power supply, you can set the trigger source to the AC power supply, use one channel to measure the AB waveform first, then store it as a reference waveform, and then use the probe to connect BC. At this time, the phase shift can be measured.

3. What is confounding inhibition ?

A: Aliasing refers to a condition that occurs when the frequency collected by the oscilloscope is lower than twice the maximum frequency of the actual signal. Aliasing suppression is specially designed to prevent aliasing. Aliasing suppression can determine the maximum frequency of the signal and collect the signal at twice the maximum frequency.

4. How to capture non-periodic signals ?

A: ①. Set the trigger level to the required value. ②. Click the main control button SINGLE, the machine starts waiting. If a signal reaches the set trigger level, it will be sampled once and displayed on the screen. This function can easily capture accidental events, such as sudden glitches with large amplitudes: set the trigger level to just above the normal signal level, click the SINGLE button, and when the glitch occurs, the machine will automatically trigger and record the waveform before and after the trigger. Drag the trigger position mark 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 consistent with the channel of the actual measured signal input). ③. Click the A1 or A2 button and select the coupling mode as AC (alternating current) coupling. ④. Adjust the sampling rate and vertical sensitivity until a satisfactory display is obtained.

6. In what situations can the acquisition method of DS5000 oscilloscope be used ?

A: To observe a single signal, please use the real-time sampling method. To observe a high-frequency periodic signal, you can use the equivalent sampling method. To observe the envelope of the signal to avoid confusion, please use the peak detection method. To reduce the random noise in the displayed signal, please use the average sampling method. The number of averages can be selected. To observe a low-frequency signal, select the rolling mode method. To display a waveform close to the effect of an analog oscilloscope, please use the analog acquisition method.

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

A: For different types of oscilloscopes, different capture modes, and different relationships between triggering and waveform acquisition. If it is a sampling oscilloscope or a real-time oscilloscope in equivalent time sampling mode, the acquisition of a waveform requires multiple triggers. For the real-time sampling mode of a real-time oscilloscope, the waveform will definitely be acquired once it is triggered. Even if it is not triggered, the waveform may still be acquired. This is the AUTO mode of the trigger. (There are three trigger modes, one is AUTO. Even if it is not triggered, the waveform will be refreshed, but the waveform will be unstable on the screen. Another is NORMAL, which is refreshed only when it is triggered. The last one is SINGLE. The waveform is captured for the first time it is triggered, and it will not be captured again in the future.).

8. Can RIGOL products automatically generate EXCEL tables after saving waveform data ? Answer: Yes. Ultrascope software can automatically save the waveform data after downloading as an Excel table file format. The RVO virtual instrument does not have the function of automatically generating Excel tables in the software, but we provide a conversion tool (free download on the official homepage of RIGOL, software name: DatKit for RVO3000&4000 Series). With this tool, you can convert RVO saved in "*.dat" file format to "*.txt" text file format, and modify txt to xls to save the data in an Excel table.

9. After collecting the signal, the signal waveform does not appear on the screen. How to deal with it ?

A: You can check and handle it according to the following steps: 1. Check whether the probe is properly connected to the signal connection line; 2. Check whether the signal connection line is properly connected to the BNC (i.e. channel connector); 3. Check whether the probe is properly connected to the object under test; 4. Check whether the object under test generates a signal (you can connect the channel with the problematic channel together to determine the problem). 5. Collect the signal again.

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

A: There are two typical applications for glitch/pulse width triggering. One is to synchronize circuit behavior, such as using it to synchronize serial signals, or for applications with very serious interference, edge triggering cannot be used to correctly synchronize signals, and pulse width triggering is an option; the other is to find abnormal phenomena in signals, such as narrow glitches caused by interference or competition. Since this abnormality appears occasionally, it must be captured by glitch triggering (another method is peak detection, but the peak detection method may be limited by its maximum sampling rate, and at the same time, it can generally be seen but not measured). If the pulse width of the object being measured is 50ns, and there is no problem with the signal, that is, there is no signal distortion or narrower caused by interference, competition, etc., the signal can be synchronized using edge triggering without using glitch triggering.

11. When choosing an oscilloscope, the most important consideration is usually bandwidth. Under what circumstances should the sampling rate be considered ?

A: It depends on the object being measured. Under the premise of satisfying the bandwidth, it is hoped that the minimum sampling interval (the inverse of the sampling rate) can capture the signal details you need. There are some empirical formulas for sampling rate in the industry, but they are basically derived for the bandwidth of the oscilloscope. In practical applications, it is best not to use an oscilloscope to measure signals of the same frequency. If you are selecting a model, for a sine wave, the bandwidth of the oscilloscope should be 3 times the frequency of the sine signal being measured. The sampling rate is 4 to 5 times the bandwidth, which is actually 12 to 15 times the signal. For other waveforms, ensure that the sampling rate is sufficient to capture the signal details. If you are using an oscilloscope, you can verify whether the sampling rate is sufficient by the following methods: Stop the waveform and enlarge the waveform. If you find that the waveform has changed (such as certain amplitudes), the sampling rate is not enough, otherwise it is fine. You can also use point display to analyze whether the sampling rate is sufficient.

12. How to eliminate glitches when using an oscilloscope ?

A: If the burr is inherent in the signal itself, and you want to use edge triggering to synchronize the signal (such as a sine signal), you can use the high-frequency suppression trigger method, which can usually synchronize the signal. If the signal itself has burrs, but you want the oscilloscope to remove the burrs and not display the burrs, it is usually difficult to do so. You can try to use the bandwidth limitation method, but if you are not careful, you may also filter out part of the signal itself. If you use a logic analyzer, generally speaking, using the state acquisition method, some of the glitches collected in the timing mode will not be visible.

13. What kind of signals are suitable for measuring the various trigger applications of the DS5000 oscilloscope, such as edge trigger, pulse width trigger and video trigger ?

A: Edge triggering can set the trigger level, rising edge or falling edge. Edge triggering is also called basic triggering. Pulse width triggering can determine the triggering time according to the pulse width. You can capture abnormal pulses by setting the pulse width condition. Video triggering can trigger on the field or line of NTSC, PAL or SECAM standard video signals.

14. Using the DS5000 series oscilloscope, how can you completely capture and save a one-time random signal, and then replay and analyze it ?

Answer: If the so-called random signal being measured is a single signal, then just set the vertical and horizontal scales to match the signal, adjust the trigger level, use a single trigger to wait for the signal to appear, and then use the waveform saving function of the STORAGE storage type to store the captured waveform. If you need to replay the saved waveform, you only need to call out the waveform to replay the analysis.

15. Why do we need to store the settings when the waveform storage has already stored them? What is the use of storing the settings ?

A: First of all, the main difference between the two is that the storage space occupied by waveform storage is much larger than that of setting storage. Therefore, considering the storage space and cost, the two need to be saved separately. Secondly, there are also differences in the call-out of the two. The waveform call-out oscilloscope is in the STOP state, and the saved running state is not changed when the setting is called out, which can facilitate direct observation of the waveform.

16: Every oscilloscope has a frequency range, such as 10M, 60M, 100M... The oscilloscope I use is nominally 60MHz. Can it be understood that it can measure up to 60MHz? But I can't measure the 4.1943MHz square wave with it. What's the reason ?
Answer: A 60MHz bandwidth oscilloscope does not mean that it can measure 60MHz signals well. According to the definition of oscilloscope bandwidth, if a 60MHz sine wave with a peak-to-peak value of 1V is input to a 60MHz bandwidth oscilloscope, you will see a 0.707V signal on the oscilloscope (30% amplitude measurement error). If you test a square wave, the reference standard for selecting an oscilloscope should be the signal rise time. The oscilloscope bandwidth = 0.35/signal rise time × 3. At this time, your rise time measurement error is about 5.4%. The probe bandwidth of the oscilloscope is also very important. If the system bandwidth of the oscilloscope probe used, including its front-end accessories, is very low, the oscilloscope bandwidth will be greatly reduced. If a probe with a bandwidth of 20MHz is used, the maximum bandwidth that can be achieved is 20MHz. If a 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 impact on square waves of about 4MHz because the speed is not very fast. In addition, you should also look at the oscilloscope manual. Some 60MHz oscilloscopes will have a sharp reduction in actual bandwidth to below 6MHz under a 1:1 setting. For a square wave of about 4MHz, its third harmonic is 12MHz and its fifth harmonic is 20MHz. If the bandwidth is reduced to 6MHz, the signal amplitude will be greatly attenuated. Even if the signal can be seen, it is definitely not a square wave, but a sine wave with attenuated amplitude. Of course, there may be many reasons for not being able to measure the signal, such as poor contact of the probe (this phenomenon is easy to eliminate). It is recommended to connect a function generator with a BNC cable to check whether there is any problem with the oscilloscope itself and the probe. If there is any problem, you can contact the manufacturer directly.

17: Oscilloscope Basics