“Of all the test equipment that Electronic engineers and technicians use, the most useful is undoubtedly the oscilloscope. Oscilloscopes are powerful enough to help electronics engineers and technicians quickly and accurately capture time-varying Voltage (or other parameters such as current) measurements that no other device in the lab can easily accomplish.
Of all the test equipment that electronic engineers and technicians use, the most useful is undoubtedly the oscilloscope. Oscilloscopes are powerful enough to help electronics engineers and technicians quickly and accurately capture time-varying voltage (or other parameters such as current) measurements that no other device in the lab can easily accomplish.
Oscilloscopes are widely used in manufacturing, circuit design, and other industries, and are essential tools for troubleshooting, signal integrity, and a simple understanding of how electronic circuits work.
Although the entire set of keys, knobs, probes, and associated probe accessories and color displays of modern oscilloscopes can seem complicated, it can be repulsive to anyone who wants to learn. But in fact, don’t let the complex appearance of the oscilloscope intimidate, it is a very simple and easy-to-use device with a few basic skills. Moreover, the current advanced oscilloscopes will also have full touch function, which means that all the original complex button and knob operations can be replaced by Touch Screen operations. If you’ve experienced the early pushbutton phones and today’s smartphones, you’ll quickly understand the advantages of touchscreens.
The key to becoming an oscilloscope expert is to first understand the basics of oscilloscopes, and then use that basic knowledge to expand your learning. The following brief article will introduce these aspects, some key points and common problems encountered by some new users in the basic use of the oscilloscope. This will help us quickly understand the oscilloscope and find the right learning direction. As the learning time lengthens, after a certain time with an oscilloscope, we can make almost any measurement and eventually become more proficient and professional in the field of testing.
For the sake of simplicity, this article only introduces the smart oscilloscope with full touch and Android system, the STO1104C, as an example. For old-fashioned traditional analog oscilloscopes, they have been obviously eliminated with the progress of the times, and they will no longer be used. repeat.
Grounding and Safety
Before learning the basics of an oscilloscope, let’s learn about proper grounding and safety of the oscilloscope to avoid personal injury and damage to the oscilloscope or any accessories connected to the oscilloscope. Improper connection of the probe can create a current path that can damage the probe. To avoid electric shock, the oscilloscope must be connected to the earth through the ground wire. In short, the metal part of the probe is connected to the oscilloscope directly through the oscilloscope’s power lead to safety ground.
You can try changing the connection yourself using an ohmmeter. This is a low impedance connection, when the circuit under test is also connected to ground, a loop is formed, and very low impedance can cause excessive current in the circuit. The current-carrying capacity of the probe’s ground lead quickly exceeds its rating, the lead is suddenly disconnected, and you may hear a loud bang!
The best way to fix this is to break the ground loop by isolating the circuit under test or isolating the oscilloscope ground. If the oscilloscope’s safety ground fails, your best bet is to ensure that the circuit under test is not connected to the ground safety ground. Use an isolated oscilloscope or differential probe, or choose to use an isolated power supply or battery to power your test circuit. Be careful when using something like a USB connector to power the circuit under test, as these kinds of devices are usually not isolated from ground and still suffer from ground loop problems.
What is an oscilloscope?
An oscilloscope can measure the voltage waveform of the signal under test by means of a voltage sensor (i.e. the most common oscilloscope voltage probe) or some other sensor such as a pressure sensor, current probe, noise meter, etc. The graph produced by an oscilloscope measures voltage on the vertical axis and represents signal time on the horizontal axis. From the captured waveform, we can obtain data such as frequency, amplitude, period, phase, distortion, noise, DC, AC, duty cycle, rise/fall time of the signal, etc.
In addition to the Display, there are three other important functions that make up an oscilloscope. These functions are oscilloscope triggers, volts per division vertically, and time per division horizontally.
The trigger function is used to synchronize the horizontal sweep of the signal, which is very important for us to observe the signal. Triggers make repeating waveforms appear stationary on the Display by repeating the triggered portion of the input signal. The most basic and common triggering method in an oscilloscope is edge triggering. This is the trigger method most people will most likely use when they first start using an oscilloscope. In addition to this, oscilloscopes have many other special and even complex triggering methods for responding to specific conditions and can really make an oscilloscope a powerful measurement tool. These triggers include pulse width trigger, logic trigger, N-edge trigger, runt trigger, slope trigger, timeout trigger, video trigger, serial bus trigger, etc.
Vertical scale (volts/div)
By adjusting the vertical scale of the oscilloscope, you can zoom in and out the shape of the waveform in the vertical direction. For example, if we set the vertical scale to 1V/div, and the oscilloscope has 10 divisions in the vertical direction, then the entire screen of the oscilloscope can display a waveform of up to 10V. It should be noted that this value is also related to the attenuation ratio of the probe. If we use a 10X probe, but we do not adjust the attenuation ratio of the oscilloscope channel (the default is 1X), then the correct reading will be the actual reading. The difference is 10 times. Therefore, when using the oscilloscope, you should also pay attention to the attenuation ratio of the probe. It is only necessary to adjust the attenuation ratio of the channel and the attenuation ratio of the probe.
Input coupling is another simple yet commonly overlooked or misunderstood feature in oscilloscopes. It refers to the connection method used to connect electrical signals from one circuit to another, that is, from the circuit under test to the oscilloscope. You can set the input coupling method to DC coupled DC, AC coupled AC or ground coupled. AC coupling only blocks the DC portion of the signal from passing, and you’ll see a waveform centered on zero scale on the display. Ground coupling disconnects the input signal of the vertical control, allowing you to see where the zero level is on the display. The DC-coupled setting allows all input signals to be displayed, both DC and AC.
Horizontal scale (time/div)
The horizontal scale function, also called the time base, can determine the time the waveform occupies on the display. Similar to the above-mentioned vertical scale control, the horizontal scale control can also scale the waveform. Relative to the vertical scale control, the vertical direction of the waveform is controlled, and the horizontal scale control is the horizontal direction of the waveform. If the time base is set to 10ms, each horizontal grid on the display represents 10ms, and the entire screen (assuming a total of 14 grids on the display) is equal to 140ms, which means that the entire waveform displayed is 140ms long. By changing the time The base size makes it easy to observe longer or shorter time intervals of the input signal.
In the attitude towards the speed of the signal, most people generally only care about the frequency of the signal, but do not care about the rise time of the signal. In a standard sine wave, rise time versus frequency is a simple mathematical relationship, and a typical formula for determining whether an oscilloscope’s bandwidth is sufficient is 0.35 divided by the rise time. For example, a pulse with a rise time of 1ns needs to be measured, which means that the minimum bandwidth of the oscilloscope should be around 350MHz. But in practice, Fourier tells us that the actual waveform is the product of a mixture of fundamental and higher harmonics. Therefore, the higher the harmonic proportion of the waveform, the shorter the rise time. Compared with the frequency of the signal, the rise time can better represent the speed of the signal. So don’t underestimate the low-frequency signal, as long as its rising edge bursts in an instant, it is enough to cause a series of problems such as signal ringing, reflection, and overshoot.
Sample rate (Samples/second) and memory depth are another important consideration for an oscilloscope. The sample rate represents the ability of the oscilloscope to acquire the number of data points per second. The higher the sample rate, the more realistic and detailed the oscilloscope will display the waveform, and the less likely it is that critical information will be lost. If you are measuring a sine wave, a general rule of thumb is that the sampling rate of the oscilloscope should be at least 2.5 times the highest frequency component of the signal you are measuring. Whereas if measuring square waves, pulses and other signal types, the sampling rate should be at least 10 times the highest frequency component of the signal to be measured. The memory depth represents the maximum number of sampling points that the oscilloscope can save on one screen. If the oscilloscope’s ability to sample data is sufficient, but the ability to store data is insufficient, then a larger sampling rate is in vain. It’s like pouring a glass of water, no matter how big the opening of the kettle is and how fast the water is poured, if our glass is too small, it can’t hold much water. Sampling rate = storage depth ÷ waveform recording duration, this is the relationship between the three. The waveform recording duration is a parameter we control. The other two items are generally fixed parameters (oscilloscopes with large memory depth can also adjust the memory depth, but the upper limit is fixed).
About the knowledge of the probe of the oscilloscope, it is no exaggeration to start another article. The probe that most of us use the most should be a passive probe with a 1X or 10X attenuation ratio. When using the probe, pay attention to the maximum peak-to-peak voltage that the probe can withstand to prevent the capacitive load of the circuit under test from being too large. To measure high-speed signals, we often need active probes or differential probes.
With the development and rise of domestic oscilloscopes, oscilloscopes are no longer a luxury for ordinary electronics enthusiasts, but become a test instrument that most people can own. In the low-end field of oscilloscopes, the cost-effectiveness of domestic oscilloscopes has completely beaten those imported oscilloscopes. Therefore, for most people, buying a domestic oscilloscope is a very good choice!
write at the end
Oscilloscopes are the main instrument for product development and testing. They may seem complicated at first, but they are actually very easy to get started with. Just remember a few basics, use her a lot, and you’ll soon be considered your company’s oscilloscope expert. With the continuous improvement of the complexity and operating frequency of electronic equipment systems, there are bound to be more and more application scenarios that require oscilloscopes. Considering the long service life of oscilloscopes, it is very cost-effective to own and use an oscilloscope early.