If you are a scientist yourself or simply an inquisitive person, and you often watch or read the latest news in the field of science or technology. It is for you that we have created such a section, which covers the latest world news in the field of new scientific discoveries, achievements, as well as in the field of technology. Only the latest events and only verified sources.
In our progressive times, science moves at a fast pace, so it is not always possible to keep up with them. Some old dogmas are crumbling, some new ones are being put forward. Humanity does not stand still and should not stand still, and the engine of humanity is scientists and scientific figures. And at any moment a discovery can occur that can not only amaze the minds of the entire population of the globe, but also radically change our lives.
Medicine plays a special role in science, since man, unfortunately, is not immortal, is fragile and very vulnerable to all kinds of diseases. Many people know that in the Middle Ages people lived on average 30 years, and now 60-80 years. That is, life expectancy has at least doubled. This was, of course, influenced by a combination of factors, but it was medicine that played a major role. And, for sure, 60-80 years is not the limit of an average life for a person. It is quite possible that someday people will step over the 100-year mark. Scientists from all over the world are fighting for this.
Developments are constantly underway in the field of other sciences. Every year, scientists from all over the world make small discoveries, little by little moving humanity forward and improving our lives. Places untouched by man are being explored, primarily, of course, on our home planet. However, work is constantly happening in space.
Among technology, robotics is especially rushing forward. The creation of an ideal intelligent robot is underway. Once upon a time, robots were an element of science fiction and nothing more. But already at the moment, some corporations have real robots on their staff that perform various functions and help optimize labor, save resources and perform hazardous activities for humans.
I would also like to pay special attention to electronic computers, which 50 years ago took up a huge amount of space, were slow and required a whole team of employees to maintain them. And now there is such a machine in almost every home, it is already called more simply and briefly - a computer. Now they are not only compact, but also many times faster than their predecessors, and anyone can understand it. With the advent of the computer, humanity opened a new era, which many call “technological” or “information”.
Remembering about the computer, we should not forget about the creation of the Internet. This also gave a huge result for humanity. This is an inexhaustible source of information, which is now available to almost every person. It connects people from different continents and transmits information at lightning speed, something that would have been impossible to even dream of 100 years ago.
In this section, you will certainly find something interesting, exciting and educational for yourself. Perhaps even someday you will be able to be one of the first to learn about a discovery that will not just change the world, but will change your mind.
Currently, it is difficult to keep up with the latest radio electronics technologies. A variety of electronic devices can now be modified to suit your taste from one to another. There would be desire and ability. Even from an old electronic clock you can make a simple tester for many electrical circuit parts, not to mention tablets and computers. Many radio amateurs and professionals often have to use precision electronic instruments, among which the oscilloscope is very popular. Such a good device is not cheap. Although making it yourself using a tablet and Android will not be difficult even for a radio amateur.
What is an oscilloscope and its functions
For those who are not particularly familiar with the operation of an oscilloscope and its visual views, I will explain. This is a device (in the old version like a mini-TV, in the new version - a tablet design, etc.) that measures and tracks frequency fluctuations in the electrical network. In practice, it is widely used by many specialized laboratories and professional radio and television technicians. Since precise settings of many electrical appliances are made only with its help.
Its readings in electronic or paper form allow you to see sinusoidal waveforms. The frequency and intensity of this signal, in turn, allows determine the malfunction or incorrect assembly of the electrical circuit. Today we will look at a two-channel oscilloscope, which you can assemble with your own hands based on the existing circuits of a smartphone, tablet and the corresponding software.
Assembling a pocket oscilloscope based on Android
The measured frequency must be audible to the human ear, and the signal level must not exceed standard microphone sound. In this case, you can assemble an Android-based oscilloscope with your own hands without additional modules. Disassembling the headset, on which there is a microphone. If you do not have this headset, you will need to purchase a 3.5 mm audio plug with four contacts. Solder the probes according to the connectors of your gadget.
Download software from the Market that will measure the frequency of the microphone input and draw a graph based on this signal. The presented options will be enough to choose the best one. After calibrating the application, the oscilloscope will be ready for use.
Pros and cons of the “Android” build:
Assembling an oscilloscope from a tablet
To stabilize the signal and expand the input voltage range, you can use an oscilloscope circuit for a tablet. It has been used for a long time and successfully to assemble devices for the computer.
For this purpose, KS 119 A zener diodes with resistors of 10 and 100 kOhm are used. The first resistor and zener diodes are connected in parallel. Second and more powerful resistor connected to the input of the electrical circuit. This expands the maximum voltage range. Ultimately, additional interference disappears and the voltage increases to 12 volts.
A special feature of the tablet oscilloscope is that it works directly with sound pulses and unnecessary interference (shielding) of the circuit and probes in this case will be undesirable.
Necessary software for assembling an oscilloscope based on a tablet and Android
To work with such a circuit, you will need a program that can draw graphs based on the incoming audio signal. Many such options can be easily found in the Market. With their help you can select additional calibration and achieve maximum accuracy for a professional oscilloscope from a tablet or other functional device.
Wideband frequency using a separate gadget
A wide range of frequencies using a separate gadget is achieved by its set-top box with an analog-to-digital converter, which provides signal transmission in digital version. Due to this, higher measurement accuracy is achieved. In practice, it is a portable display that accumulates information from individual devices.
Oscilloscope from an Android tablet
Bluetooth channel
Currently, with electronic progress, consoles appear in stores that perform the functions of an oscilloscope. They transmit a signal using a Bluetooth channel to a tablet or smartphone. Such an oscilloscope is an attachment, connected to tablet via Bluetooth has its own characteristics. The measured frequency limit of 1 MHz, the probe voltage of 10 V and the range of about 10 meters are not always sufficient for the professional range of work activities. In such cases, you can use an oscilloscope - a set-top box with data transmission using Wi-Fi.
Transfer data using Wi-Fi
Wi-Fi significantly expands the capabilities of measuring devices. This type of information exchange between the tablet and the set-top box is especially popular. This is not a fashion statement, but pure practicality. Since the measured information is transmitted without delay to the tablet, which instantly displays any graph on its monitor.
A clear user menu allows you to quickly and easily navigate the controls and settings of the electronic device. A recording device allows you to reproduce and transmit information in real time and to all points for all participants in this process.
Usually, along with the purchased oscilloscope set-top box, a disk with software is supplied. These drivers and program You can quickly download it to your tablet or smartphone. If there is no such disk, find this data in the application store or search on the Internet on forums and specialized sites.
DIY USB oscilloscope circuit diagram
Assembling a USB oscilloscope will cost you only 250–300 rubles and you can make it yourself.
The advantages of this device are its low cost, mobility and small size. But, unfortunately, there are more significant disadvantages. These are low sampling rate, presence of a PC, low bandwidth and memory depth.
For professionals this electronic “toy” obviously won't do. And for beginner radio amateurs, this is a very good oscilloscope simulator for acquiring certain practical skills.
A series of publications dedicated to oscilloscopes. Today I will talk about the main types of oscilloscopes, talk about their advantages and disadvantages, consider the main characteristics of oscilloscopes and try to give advice on how to choose a tool that suits the tasks being solved.
Choosing a new oscilloscope can be quite a daunting task as there are quite a few models on the market at the moment. Here are some basic points that will help you make the right decision and understand what you really need.
Before you decide to buy a new oscilloscope, try to answer the following questions for yourself:
- Where are you going to use the device?
- How many points in the circuit will you need to measure at the same time?
- What is the amplitude of the signals you typically measure?
- What frequencies are present in the signals you are measuring?
- Do you need to measure periodic or single signals?
- Are you studying signals in the frequency domain and do you need the Fast Fourier Transform function?
Analog or digital oscilloscope?
You may still be a fan of analog instruments, but in today's digital world, their features cannot match the capabilities of modern digital storage oscilloscopes. In addition, analog models may use outdated technology with very limited capabilities. There may also be problems with the availability of spare parts.
The advantage of an analog oscilloscope is the absence of noise that is inherently digital in nature, namely, there is no ADC noise, which appears in the form of a stepped oscillogram on digital instruments. If accuracy in transmitting the shape of the signal under study is very important to you, then your choice is an analog device.
The advantages of a digital oscilloscope are obvious:
Digital oscilloscopes also provide the opportunity for high-speed data acquisition and can be integrated into automatic testing systems (relevant for production).
Also, often digital devices can include additional devices in one housing:
- Digital (logical) analyzer (these devices allow, in addition, to analyze digital data packets, for example, transmitted through various interfaces I 2 C, USB, CAN, SPI and others)
- Function (arbitrary waveform) generator
- Digital Sequence Generator
If the oscilloscope is made in the form of a portable device, then it is often combined with a multimeter; they are also called scopmeters (sometimes with very good characteristics). The undeniable advantages of such devices are independence from the power supply, compactness, mobility and versatility.
USB oscilloscopes
PC-based oscilloscopes, or USB oscilloscopes as they are also called, are becoming increasingly popular because they are cheaper than traditional ones. Using a computer, they offer the benefits of a large color display, a fast processor, the ability to save data to disk, and keyboard operation. Another big advantage is the ability to quickly export data to spreadsheets.
Among USB set-top boxes, you often come across real combines that combine several devices in one housing: an oscilloscope, a digital analyzer, an arbitrary waveform generator, and a digital sequence generator.
The price of convenience and versatility is worse performance than their autonomous counterparts.
Important Features of Oscilloscopes
Let's look at what characteristics of devices you should pay attention to when choosing an oscilloscope.
1. Bandwidth
Choose an oscilloscope that has enough bandwidth to capture the high frequencies contained in the signals you are measuring.
Bandwidth is perhaps the most important characteristic of an oscilloscope. It is this that determines the range of signals that you plan to examine on the screen of your oscilloscope, and it is this parameter that significantly affects the cost of the measuring device.
For oscilloscopes with a bandwidth of 1 GHz and below, the amplitude-frequency response (AFC) of the device is the so-called Gaussian frequency response, which is the frequency response of a single-pole low-pass filter. This filter passes all frequencies below a certain cutoff frequency (which is the oscilloscope's cutoff frequency) and rejects all frequencies present in the signal above this cutoff frequency.
The frequency at which the input signal is attenuated by 3 dB is considered the oscilloscope's bandwidth. A signal attenuation of 3 dB means approximately 30% amplitude error! In other words, if you have a 100 MHz sine wave at the oscilloscope input, and the oscilloscope bandwidth is also 100 MHz, then the 1V peak-to-peak voltage measured by that oscilloscope will be about 700 mV (-3 dB = 20 lg(0.707 / 1.0). As the frequency of your sine wave increases (while maintaining a constant amplitude), the measured amplitude decreases. Therefore, you cannot make accurate measurements on signals that have high frequencies near your oscilloscope's passfrequency.
So how do you determine the required bandwidth of a device? To measure purely analog signals, you need an oscilloscope that has a stated bandwidth of at least three times higher than the highest frequency sine waves you might need to measure. At 1/3 of the oscilloscope's bandwidth, the level of signal attenuation is minimal. To measure more accurately, use the following rule: bandwidth divided by 3 is approximately 5% error, and bandwidth divided by 5 is approximately 3% error. In other words, if you will be measuring frequencies at 100 MHz, choose an oscilloscope that is at least 300 MHz, and preferably 500 MHz. But, unfortunately, this will entail an increase in price...
What about the required bandwidth for digital applications, which is where modern oscilloscopes are mostly used? As a general rule, you should choose an oscilloscope that has at least five times the bandwidth of the processor/controller/bus in your system. For example, if the maximum frequency in your own designs is 100 MHz, then you should select an oscilloscope with a bandwidth of 500 MHz or higher. If the oscilloscope meets this criterion, it will be able to capture up to the fifth harmonic with minimal signal attenuation. The fifth harmonic of a signal is critical in determining the overall shape of your digital signals. Let's look at an example: a 10 megahertz square wave consists of the sum of a 10 megahertz sinusoidal signal + a 30 megahertz sinusoidal signal + a 50 megahertz sinusoidal signal, etc. Ideally, you need to choose a device that has a bandwidth of at least the 9th harmonic frequency. So, if the main signals you work with are meanders, then it is better to take a device with a bandwidth of at least 10 times the frequency of your meanders. For 100 MHz meanders, choose a 1 GHz device, but, unfortunately, this will significantly increase its cost...
If you don't have an oscilloscope with the appropriate bandwidth on hand, when examining square wave signals, you will see rounded corners on the screen instead of the crisp, clear edges that characterize the high rise rate of the pulse. It is quite obvious that such a display of signals generally negatively affects the accuracy of the measurements performed.
Waveform distortion due to insufficient bandwidth (rectangular signal at input)
Meanders have fairly steep temporary rises and falls. There is a simple rule to find out the required bandwidth for your device if these peaks and valleys are important to you. For an oscilloscope with a bandwidth below 2.5 GHz, the steep rise (fall) can be measured as 0.35 divided by the bandwidth. Thus, a 100 MHz oscilloscope can measure a rise of up to 3.5 ns. For an oscilloscope from 2.5GHz to 8GHz, use 0.4 divided by the bandwidth and for oscilloscopes above 8GHz, use 0.42 divided by the bandwidth. If your rise is the starting point for calculations, then use the reverse: if you need to measure 100ps rise, you need an oscilloscope with a bandwidth of 0.4/100ps = 4GHz.
2. Sample rate
Select an oscilloscope that has a sufficient sampling rate on each channel to support the device's rated real-time bandwidth.
This parameter is also sometimes called sampling frequency or sampling rate.
Closely related to the real-time bandwidth of an oscilloscope is its maximum allowable sampling rate. “Real-time” means that the oscilloscope can capture and display once-acquired (non-repeating) signals commensurate with the instrument's bandwidth.
To proceed to determining the sampling frequency, you need to remember Kotelnikov’s theorem (in the West it is better known as Nyquist-Shannon theorem or sampling theorem), which states that in the case
if an analog signal has a limited spectral width, then it can be uniquely reconstructed without loss from its samples taken at the frequency title="Rendered by QuickLaTeX.com" height="16" width="84" style="vertical-align: -4px;">, где — максимальная частота, которой ограничен спектр сигнала и его можно представить в виде ряда!}
Where
and the sampling interval satisfies the condition
If the maximum frequency in the signal exceeds half the sampling frequency, then it is impossible to restore the signal without distortion.
It would be a mistake to assume that this is the oscilloscope's bandwidth. With this assumption, the minimum required sampling rate for an oscilloscope for a given bandwidth is only twice the real-time bandwidth of the oscilloscope.
Distortion of frequency components when the oscilloscope bandwidth is equal to half its sampling frequency for the case of Gaussian frequency response
as shown in the figure, this is not the same as , unless of course the oscilloscope filter works like a brick wall (doesn't cut frequencies above sharply to zero amplitude).
As I mentioned, oscilloscopes with a bandwidth of 1 GHz and below typically have a Gaussian frequency response. This means that although the oscilloscope attenuates the amplitude of the signal with frequencies above the -3 dB point, it does not completely eliminate these higher frequency components. The distorted frequency components are shown in red shading in the figure. Therefore always higher than the oscilloscope bandwidth.
It is recommended to select the maximum sampling rate of the oscilloscope at least four to five times higher than the real-time oscilloscope bandwidth, as shown in the figure below. With this setting, the oscilloscope's reconstruction filter can accurately reproduce the shape of high-speed signals with resolution in the range of tens of picoseconds.
Distorted frequency components when the oscilloscope bandwidth is set to ¼ of the instrument's sampling rate
Many wideband oscilloscopes have a sharper frequency response cutoff, as in the figure below. This is the “maximally flat” frequency response. Because an oscilloscope with the most flat frequency response attenuates frequency components outside much more, and begins to approach the ideal response of a theoretical "brick wall" filter, not many sample points are required to give a good representation of the input signal when using digital filtering to reconstruct the waveform. For oscilloscopes with this type of frequency response, it is theoretically possible to specify a bandwidth equal to .
Distorted frequency components when the oscilloscope bandwidth is set to 1/2.5 of its sampling frequency for devices with a “maximally flat” frequency response.
3.Memory depth
Choose an oscilloscope that has enough memory depth to capture your most complex, high-resolution signals
Closely related to an oscilloscope's maximum sampling rate is its maximum possible memory depth. Even though an oscilloscope's technical specifications brochure may claim a high maximum sample rate, this does not mean that the oscilloscope always samples at that high rate. The oscilloscope samples the signal at maximum speed when the sweep is set to one of the fast time ranges. But when the sweep is set to the slow range, in order to capture a larger time interval by stretching it across the oscilloscope screen, the instrument automatically reduces the sampling rate based on the available memory depth.
For example, let's assume that the oscilloscope has a maximum sampling rate of 1 Gigasample/s and a memory depth of 10 thousand points. If the oscilloscope sweep is set to 10 ns/div, then in order to capture 100 ns of the signal on the oscilloscope screen (10 ns/div x 10 sections = 100 ns time span), the oscilloscope only needs 100 memory points across the entire screen. At its maximum sampling rate of 1 Gigasample/s: 100 ns time interval x 1 Gigasample/s = 100 points. No problem! But if you set the oscilloscope sweep to 10 µs/div to capture 100 µs of signal, the oscilloscope will automatically reduce its sampling rate to 100 Megasamples/s (10 thousand points / 100 µs time span = 100 Megasamples/s). Maintaining the oscilloscope's high sampling rate over slow time ranges requires the instrument to have additional memory. A fairly simple equation will help you determine the amount of memory required, based on the longest time span of the complex signal you need to capture and the maximum sample rate at which you want the oscilloscope to sample.
Memory = Time Interval x Sampling Rate
While you may intuitively think that more memory is always better, oscilloscopes with greater memory depth tend to be more expensive. Secondly, processing long signals using memory requires additional time. This usually means that the waveform update rate will be reduced, sometimes significantly. For this reason, most oscilloscopes on the market today have a manual selection of memory depth, and the typical default memory depth setting tends to be relatively small (10 to 100 thousand points). If you want to use deep memory, then you have to manually enable it and compromise on waveform update speed. This means you need to know when to use deep memory and when not to.
Memory segmentation
Some oscilloscopes have a special operating mode called memory segmentation. Segmented memory can effectively extend the acquisition time by dividing the available memory into smaller segments, as shown in the figure below. The oscilloscope then selectively digitizes only the important parts of the waveform of interest at a high sampling rate and then timestamps it so you know the exact time between each occurrence of a trigger event. This allows the oscilloscope to capture many consecutive single-shot signals with very short repetition times without missing important information. This mode of operation is especially useful when capturing signal bursts. Examples of pulse-type signals are pulsed radar, laser flashes, and packetized serial data bus signals.
4. Number of channels
Choose an oscilloscope that has enough channels to make time-critical measurements between correlated signals.
The number of channels required in the oscilloscope will depend on how many signals you need to simultaneously observe and compare with each other. The heart of most embedded systems today is the (MCU), as simplistically shown in the figure below. Many microcontroller systems are, in fact, mixed-signal devices with multiple analog, digital, and serial I/O buses to communicate with the outside world, which is always analog in nature.
Today's mixed-signal designs are becoming more complex and may require more channels in the oscilloscope to capture and display them. Two and four channel oscilloscopes are in demand today. Increasing the number of channels from 2 to 4 does not lead to a doubling of the price of the device, but still the price increases significantly. Two channels are optimal, a larger number of channels depends on your needs and financial capabilities. More than four analog channels are very rare, but another interesting option is a mixed-signal oscilloscope.
Mixed-signal oscilloscopes combine all the measurement capabilities of an oscilloscope with some of the capabilities of logic analyzers and serial bus protocol analyzers. Most important is the ability of these instruments to simultaneously capture multiple analog and logic signals while simultaneously displaying the waveforms of those signals. Think of it as having several channels with high vertical resolution (usually 8 bits) plus several additional channels with very low vertical resolution (1 bit).
The figure below shows an example of capturing a digital-to-analog converter (DAC) input signal using the oscilloscope's digital channels, while simultaneously monitoring the DAC signal output using one analog channel. In this example, the mixed signal oscilloscope is configured such that it will trigger if the logic state of the DAC input reaches its lowest value of 0000 1010.
A mixed-signal oscilloscope can capture and display multiple analog and digital signals simultaneously, providing an overall picture of correlated processes
5. Waveform update rate
Choose an oscilloscope that has a high enough waveform update rate to capture random and infrequent events for faster debugging of projects.
Waveform update rate can be as important as the bandwidth, sample rate, and memory depth we've already discussed, although this is often an overlooked parameter when comparing different oscilloscopes before purchasing. Even though an oscilloscope's waveform update rate may appear high when viewing recaptured signals on your oscilloscope's display, this "fast rate" is relative. For example, an update of several hundred signals per second is certainly fast enough, but from a statistical point of view, it may not be sufficient to capture a random or rare event that may only occur once in a million signals captured.
When debugging new projects, waveform update speed can be critical—especially when you're trying to find and debug infrequent or intermittent problems. Increasing the waveform update rate increases the likelihood that the oscilloscope will capture “ghost” events.
An integral characteristic of all oscilloscopes is “dead time” ( dead-time) or "blind time" ( blind time). This is the time between each repeated acquisition of a signal by the oscilloscope during which it processes the previously acquired signal. Unfortunately, the dead time of an oscilloscope can sometimes be several orders of magnitude longer than the acquisition time. During the oscilloscope's dead time, any signal activity that may occur will be missed, as shown in the figure below. Note the pair of signal spikes that occurred during the oscilloscope's idle time, rather than during acquisition time.
Acquisition time and oscilloscope dead time
Because of dead time, capturing random and rare events with an oscilloscope becomes a game of chance, much like rolling dice. The more times you roll the dice, the higher the probability of getting a certain combination of numbers. Likewise, the more frequently an oscilloscope's waveforms are updated for a given observation time, the greater the likelihood of capturing and viewing an elusive event that you may not even suspect exists.
The figure below shows a surge that occurs approximately 5 times per second. Some oscilloscopes have a maximum waveform update rate of over 1 million waveforms per second, and such an oscilloscope has a 92% chance of capturing this glitch within 5 seconds. In this example, the oscilloscope captured the glitch multiple times.
Capturing spikes in an oscilloscope at 1 million waveform updates per second
For oscilloscopes that update 2-3 thousand times per second, the probability of capturing such spikes within 5 seconds is less than 1%.
6.Trigger
Choose an oscilloscope that has the various trigger types you may need to help highlight signal capture on the most complex signals.
If the oscilloscope's sweep trigger has nothing to do with the signal being examined, the image on the screen will fluctuate or be blurred. In this case, the oscilloscope displays different parts of the observed signal at the same place. To obtain a stable image, all oscilloscopes contain a system called a trigger. A trigger delays the start of an oscilloscope sweep until certain conditions are met.
The trigger capability is one of the most important aspects of an oscilloscope. Triggering allows you to synchronize the oscilloscope's acquisition of a signal and display individual parts of the signal. You can think of triggering an oscilloscope as synchronized snapshots.
The most common type of oscilloscope trigger is a trigger when a certain level is crossed. For example, channel 1 edge triggering occurs when the signal crosses a certain voltage level (trigger level) in the positive direction, as shown in the figure below. All oscilloscopes have this capability, and it is probably the most commonly used trigger type. But as digital projects become more complex, you may need to further define/filter the oscilloscope trigger with specific combinations of input signals in order to capture the signal at zero, as well as view the desired portion of the complex input signal.
Triggering the oscilloscope on the edge of a digital pulse
Some oscilloscopes have the ability to trigger on pulses, with specific timing characteristics. For example, only trigger when the pulse width is less than 20 ns. This type of trigger (with refined pulse width) can be very useful for triggering on unexpected faults.
Another type of trigger that most modern oscilloscopes use is pattern triggering. Pattern trigger mode allows you to configure the oscilloscope trigger to trigger on a logic/Boolean combination of high levels (ones) and low levels (zeros) on two or more input channels. This can be especially useful when using a mixed signal oscilloscope, which may have up to 20 analog and digital channels.
More advanced oscilloscopes even provide triggers that are synchronized with waveforms that have parametric disturbances. In other words, the oscilloscope is triggered only if the input signal violates a particular parametric condition, such as a decrease in pulse amplitude ("short trigger"), an edge speed violation (rise/fall time), or perhaps a data period time violation (setup time trigger). and retention).
The figure below shows the oscilloscope triggering a positive pulse with reduced amplitude using the short trigger mode. If this stub pulse occurs only once every million digital stream pulse cycles, then capturing this signal using standard edge triggering is like looking for a needle in a haystack. It is also possible to trigger with negative short pulses, as well as short pulses with a certain duration.
Triggering the oscilloscope with a short pulse
7. Working with serial interfaces
Serial interfaces such as I 2 C, SPI, CAN, USB etc. are common in many modern digital and mixed signal designs. An oscilloscope is required to verify that the message is being transmitted correctly on the bus, as well as to make analog measurements of the signal. Many technicians use a technique known as “visual bit counting” to test a serial bus with an oscilloscope. But this manual method of decoding the serial bus is quite labor-intensive and leads to frequent errors.
Many of today's digital and mixed-signal oscilloscopes have additional serial bus protocol decoding and triggering capabilities. If you plan to work heavily with the serial bus, then look into oscilloscopes that can decode and trigger data from the serial bus, which can save you a lot of time when debugging devices.
8. Signal measurements and analysis
One of the main advantages of a modern digital storage oscilloscope, compared to analog instruments, is the ability to perform various automatic measurements and analyze digitized signals. Almost all modern digital oscilloscopes have the ability to perform manual cursor/marker measurements, as well as a minimum set of automatic measurements of pulse parameters, such as rise time, fall time, frequency, pulse width, etc.
While pulse measurements typically perform time or amplitude measurements on a small portion of the signal to provide an "answer" such as rise time or peak-to-peak voltage, the oscilloscope's math functions perform math on the entire waveform or pair of signals to produce another signal.
The figure below shows an example of a fast Fourier transform (FFT) math function that has been applied to a clock signal (yellow curve). The FFT has translated the signal into the frequency domain (gray curve), which plots amplitude in dB on the vertical axis versus frequency in Hz on the horizontal axis. Other mathematical operations that can be performed on digitized signals are summation, difference, differentiation, integration, etc.
Although mathematical functions on a signal can also be performed offline on a PC (for example, in MatLab), having this capability built into the oscilloscope can not only simplify the execution of these operations, but also observe the behavior of the signal over time.
9. Oscilloscope probes (measuring leads)
The quality of measurements very much depends on what kind of probe you connected to the BNC input of the oscilloscope. When you connect any measurement system to the circuit under test, the test instrument (and probe) becomes part of the device under test. This means that it is possible to "load" or change the behavior of your signals to some extent. Good probes should not disturb the input signal and should ideally provide the oscilloscope with an exact duplicate of the signal that was present at the measurement point.
When you buy a new oscilloscope, it usually comes with a standard set of high-impedance probes—one probe for each input channel of the oscilloscope. These types of general purpose passive probes are the most common and can measure a wide range of signals relative to ground. But these probes have some limitations. The figure below shows the equivalent circuit of a typical 10:1 passive probe connected to the high-impedance input of an oscilloscope (1MΩ oscilloscope input).
Typical 1:10 passive probe model
The electrical model of any probe (passive or active) and oscilloscope can be simplified to a combination of one resistor and one capacitor connected in parallel. The figure below shows a typical oscilloscope/probe equivalent circuit for a 10:1 passive probe. For low frequencies or DC, the load is dominated by 10MΩ resistance, which in most cases should not be a problem. Although 13.5 pF does not seem like a lot of capacitance, at high frequencies the load generated by this capacitance can be significant. For example, at 500 MHz the reactance of the 13.5 pF capacitor in this model is 23.6 ohms, which is already a significant load and can lead to signal distortion.
For high frequency measurements it is necessary to use active probes. "Active" means that the probe includes an amplifier located behind the probe tip. It allows you to significantly reduce the capacitive load and increase the bandwidth of the probe. Disadvantages of high-frequency active probes include their dynamic range, as well as their cost.
There are other special measurement tasks that I would like to mention. If you need to make measurements on a high-speed differential serial bus, then you should consider using a high-frequency differential active probe. If you need to measure very high voltage signals, you will need a special high voltage probe. If you need to measure current, you should consider using a current sensor.
We decided to take an oscilloscope to a friend. We thought for a long time... Spend 5-10 thousand for a Soviet Tseshka, or save up for a normal stuffed one, which I now have on sale
For some reason, Soviet oscilloscopes on Avita are still very expensive, and a digital oscilloscope is even more expensive. And then we thought: “Why not take a USB oscilloscope from Aliexpress?” The price is a penny, the functionality is almost the same as that of a digital oscilloscope, and the dimensions are small. A USB oscilloscope is essentially a digital oscilloscope, but with one difference - it does not have its own display.
We scratched our heads and thought about it... The crisis will last for a long time. The dollar is not going to get cheaper. The best investments are in equipment and education. Well, said and done. More than a month later, this USB oscilloscope arrived:
In addition, 2 probes, a USB cable, consumables, a software disk, and a screwdriver for adjusting the probes were included with it.
On one side of the oscilloscope, we see two BNC connectors for connecting probes, and on the right we see two pins. These pins are a test signal generator for calibrating oscilloscope probes. One of them is ground, and the other is signal.
As we can see in the photo, the maximum voltage that we can supply to the BNC connectors is 30 Volts, which is quite enough for a novice electronics engineer. The test signal generator gives us a rectangular meander signal with a frequency of 1 kilohertz and a swing of 2 volts.
On the other side, you can see a signal LED signaling the operation of the oscilloscope, as well as an input for a USB cable, which clings to a PC with the other end.
In working order it all looks something like this:
Oscilloscope operation
After installing the software that came on the disk, we hook up our oscilloscope. Driver installation begins. Then we launch the program. The program interface is simpler than a steamed turnip:
On the left is the working field itself, and on the right is the horizontal and vertical scan for the first and second channels. There is also a magical “AUTO” button, which gives us a ready-made signal on the display.
Next, click on “CH1”, which means “first channel”, since I picked up the first channel connector. We attach the probe to the test pins and prepare the oscilloscope for work. We turn the screw on the probe and ensure that the waveform of the test signal is strictly rectangular
It should look something like this:
This is done the same way on all digital oscilloscopes. You can read how to do this.
You can also display the parameters that the oscilloscope would immediately show on the monitor. These are frequency, period, average, rms, peak-to-peak voltage, etc. You can read about these parameters in this article.
Sampling frequency
Sampling frequency– this is roughly speaking, at what frequency the oscilloscope records the signal. As you know, an oscillogram is a curve or a straight line. Most often a curve. Remember how in algebra you drew the parabola graph y=x 2? If we took 3-4 points, then our graph turned out with kinks (in red circles)
And if we took more points, then the graph would actually turn out more correct and beautiful:
Everything is the same here! Only by X do we display time, and by Y - voltage.
Therefore, in order for the signal to be displayed on the display as accurately as possible, it is necessary to have as many of these points as possible. And the more points, the better and more correctly the signal shape is displayed. In this regard, they win an absolute victory.
In order to have as many points as possible, the sampling frequency should be as high as possible. Also, the sampling frequency is most often called sampling rate. Sample from English– sampling. Every digital oscilloscope has this sampling rate marked right on the body. It is indicated in MegaSamples, which means a million samples. This USB oscilloscope has a maximum sampling rate of 48 Megasamples per second (48MSa/s), which means that in 1 second the signal is drawn (consists) of 48 million points. Now tell me, which oscilloscope will have the most correct signal? U with a sampling frequency of 500 MSa/s or our hero of the article at 48MSa/s? Same thing)
Bandwidth
Bandwidth is the maximum frequency after which the oscilloscope begins to show signal distortion. On this USB oscilloscope the declared bandwidth is 20 Megahertz. If we measure signals over 20 megahertz, then our signals will be distorted in amplitude. Although in reality this USB oscilloscope produces a maximum of 3 Megahertz without distortion. This is not enough.
Pros of an oscilloscope
- Reasonable price and functionality. Costs several times cheaper than cool digital oscilloscopes
- Setting up and installing the software takes about 10-15 minutes
- User-friendly interface
- Small size
- Can perform operations with both direct and alternating current
- Two channels, that is, you can measure two signals at once and display them on the display
Cons of an oscilloscope
- Low sampling rate. A small lyrical digression...
- PC required
- Low bandwidth
- Memory depth is also no
Conclusion
After the OWONa digital oscilloscope, this USB oscilloscope feels like a glamorous turd. I don’t want to say that it is generally bad and that it is better not to buy it. He is very good-looking and can produce an oscillogram according to the stated characteristics of up to 20 Megahertz, but in reality it is several times less. It cost us a little less than 4,000 rubles. If it cost around 1000-2000 rubles, then it would be worth the money. In principle, for novice electronics engineers this oscilloscope will be a more or less normal solution. For intermediate and professional electronics engineers, I’ll say right away: “Save your money for a normal digital oscilloscope!”
Here is also a short video review from Soldering Iron:
For more information about how to choose an oscilloscope and what parameters you should pay attention to, read this article.
When buying a new oscilloscope, you should start with the questions that you must first answer for yourself:
- Where will the device be used?
- For what purposes do you need it?
- Do you need to measure signals at multiple points simultaneously?
- What is the amplitude (in digital terms) of the signals you are measuring?
- What is the frequency of the signals you are measuring?
- Are you measuring repeating or single signals?
- Are you conducting signal research in the frequency domain?
The main question: Analogue or Digital?
The main advantage of an analog oscilloscope is the absence of ADC noise.
You may still be a fan of analog instruments, but the modern digital world dictates its conditions, and the capabilities of analog instruments cannot be compared with digital storage oscilloscopes.
If the accuracy of transmitting the shape of the signal you are studying is not a priority for you in your observations and research, then you can safely opt for digital.
USB oscilloscope is a representative of the class of digital oscilloscopes. And they, in comparison with analog ones, have a number of advantages.
Namely:
- Small and relatively light
- Wide Bandwidth
- Single signal can be measured
- User-friendly interface
- Color display
- Ability to save and print data
- Possibility of digital signal processing (fast Fourier transform, addition, subtraction, integration, etc.)
- Possibility of using digital filtering
Often digital oscilloscopes can include additional devices in the same housing:
- Logic analyzer (allows you to analyze data packets, for example, transmitted via I2C, USB, CAN, SPI and others)
- Function (arbitrary waveform) generator
- Digital sequence generator
If the oscilloscope is made in the form of a portable device, then it is often combined with a multimeter; they are also called scopmeters (sometimes with very good characteristics).
The undeniable advantages of these devices are versatility, autonomy and small size.
Choosing a new oscilloscope is quite a difficult task, due to the fact that there is a wide selection of manufacturers and their models on the market.
If you decide to replace an old oscilloscope or purchase a device necessary for work, and you do not have a big appetite, then a USB oscilloscope may be the best choice for you. All you need to do is study the characteristics and settle on a specific manufacturer and model.
First of all please pay attention to the manufacturer. Studying various models, you will see that you should pay attention to a manufacturer that is constantly improving the software of its products and adding new features, without changing the platform.
Today we will pay attention to such manufacturers as Hantek, Instrustar, SainSmart.
- SainSmart – although it is more of a distributor
When considering models, it is worth focusing on devices with a band of 40-60 MHz. Although the latest models of equipment, in particular new LCD TVs, may soon require 100-120 MHz.
And yet, having visited forums on foreign platforms, you will be convinced that the opinions reflected in them are practically the real state of affairs. As for the reviews found on Russian-language sites and video reviews, they consist mainly of “let’s unpack” and “finally got it”, and as a bonus: “let’s install the drivers” and “poke with a probe.” And how the completion is joy and “it works.”
But it is unlikely that after this reading and viewing, you will be able to draw any real technically sound conclusion as to where you will stop.
Let's return to the assessments on foreign forums.
SainSmart (third on the list) disappeared after a few hours of studying - the product was not bad, but there was a problem with the software. There are no updates, but the existing one works with bugs. We know firsthand that software makes all the difference.
Next – (first in the list),
A reputable company produces an impressive range of models, including budget options. However, both budget and some later models have the same software, although it is quite modest. Functionality: a regular two-beam oscilloscope + a simple set of tools. No bonuses in the form of additional software with analyzing programs, etc. No. This is sad.
The output, as you see: - an example of elementary minimalism, although with the help of software it would be possible to implement a considerable amount of additional functionality and capabilities.
Our (Russian-language) reviews claim that almost the entire range of 20,40,60 MHz models is based on one board with minor conversions, and everything else is done by software.
In principle, the usual Chinese move is to make one piece of hardware and limit the potential of the lower line of models with software. But no. Different lines of models run on different chips and have different software inside. And this is attractive.
For example, you can choose the Instrustar ISDS220B 60 MHz model plus DDS generator up to 20 MHz. If you download and install the software, even in demo mode, you will really be pleased with it. You will find many settings, starting from the color and background of the interface, to a spectrum analyzer, frequency response analyzer and a sea of various tricks that even in demo mode you will have something to deal with.
And in general, the software is fresh, despite the age of the model being produced. The conclusion is that the manufacturer “keeps its hand on” the software - corrects errors and adds new functions. And this is a huge plus.
As an example:
The window in professional mode opened four forms.
The conclusion from all of the above suggests itself:
take your time, analyze, research and shop wisely. It's up to you to use it! Until the next reviews of the best models.
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