12 must-know details about using an oscilloscope

西安安泰Agitek

12 must-know details about using an oscilloscope [Copy link]

As the first tool for electronic measurement, the oscilloscope is simple to use, but not everyone knows all the details. The following are 12 small details related to oscilloscope measurement, which can be used as a small document for quick self-check of oscilloscope common sense.

1. What is the most valuable indicator of an oscilloscope?
Bandwidth, a grade-level parameter. Improving bandwidth also increases the cost.

2. How high should the sampling rate be to meet the requirements?
Generally speaking, the sampling rate is 5 times the bandwidth. For example, an oscilloscope with a bandwidth of 200M can be equipped with a sampling rate of 1G. The
pursuit of a higher sampling rate is nothing more than to catch small glitches, but these high-frequency glitches have been filtered out at the bandwidth layer, and a higher sampling rate does not bring good benefits.

3. What is the difference between normal triggering and automatic triggering?
Normal: Normal (standard) triggering, a waveform will be sampled only if there is a trigger event that meets the conditions;
Auto: Automatic triggering, after waiting for a period of time, if no trigger event that meets the conditions occurs, it will be forced to trigger and sample the waveform;
because the trigger position is random, it often causes unstable waveform display. If the above situation occurs, please use Normal mode.

4. How to capture abnormal signals with uncertain conditions?
You can use template trigger to capture.
When the template trigger is turned on, the template is actually used as a layer. It will continuously detect whether there is a waveform that touches the template area. When a waveform touches the template, a signal will be detected, and then it will be filtered and displayed.

5. Are the channels of the oscilloscope isolated?
The channels of the oscilloscope are not isolated; the ground of the oscilloscope is connected to the earth and cannot be directly connected to the neutral line;
adding an isolation transformer can indeed directly measure 220V AC power, but it is not a recommended practice. The safest and correct practice should be to use a differential probe.

6. Which is more accurate for measuring voltage, an oscilloscope or a multimeter?
The vertical resolution of a general oscilloscope is 8bit. The measurement accuracy is related to the vertical resolution and vertical gear.
The accuracy of the multimeter is much higher. The ADC of a six-and-a-half-digit multimeter can reach 24bit, and the handheld meter is far more than 8bit. The voltage value measured by the multimeter is more reliable.

7. What is the difference between the X1 gear and the X10 gear of the oscilloscope probe?
There are two core points:
different attenuation bandwidths, the signal amplitude does not attenuate in the X1 gear, and the signal attenuates to one tenth of the original in the X10 gear;
different bandwidths, the bandwidth of the X1 gear is only about 10M, while the bandwidth of the X10 gear is about 250M.

8. Do general oscilloscope probes need to be calibrated regularly?
The standard does not have clear measurement regulations for probes, but for passive probes, at least when replacing probes and switching channels, probe compensation adjustment must be performed.

9. What are the main factors that determine the price of oscilloscope probes?
The main determinants of price are of course bandwidth and function.
There are many types of oscilloscope probes with different performances, such as high voltage, differential, active high-speed probes, etc., and the prices range from a few hundred RMB to nearly ten thousand US dollars.
The probe is the part of the oscilloscope that contacts the circuit, and a good probe can provide the fidelity required for testing. To achieve this, even passive probes must have a lot of passive device compensation circuits (RC networks) inside.

10. Is there any way to use an oscilloscope to measure the working conditions of high-frequency transformers or inductor cores?
You can rely on the power analysis software that comes with the oscilloscope. There is a function - BH curve analysis, which can reflect the working state of the core, measure the dynamic inductance value, and derive the core loss.

11. Can the oscilloscope perform Fourier decomposition?
Most modern digital oscilloscopes have FFT function, but you need to pay attention to the number of points that FFT can analyze, which directly determines the accuracy of the FFT analysis results and avoids spectrum leakage. The ZDS2000 series oscilloscopes come standard with 4M point FFT analysis.

12. Can the oscilloscope perform filtering? For example, low-pass filtering of PWM waves?

Oscilloscopes generally have a bandwidth limit of 20MHz, which is a hardware filter. Some oscilloscopes also support software filters with adjustable cutoff frequencies. The ZDS2024 Plus can be infinitely adjusted from 100Hz to 100MHz.

The above are all the small details related to oscilloscope measurement. Have you remembered them all?

links234

Very useful! Thank you!

led2015

Thank you for sharing. Some people may accidentally measure something they shouldn't when using an oscilloscope, which may cause the board to burn. This is something worth noting.

SensorYoung

Thanks for sharing. Many of the problems mentioned here are what I have thought about but never paid attention to when using an oscilloscope.