|Topics covered in this article:|
|Ⅰ. What is Oscilloscope?|
|Ⅱ. How to use the Oscilloscope?|
|Ⅲ. How to optimize Oscilloscope performance?|
|Ⅳ. How to quickly choose the right Oscilloscope?|
An oscilloscope, formerly known as an oscillograph, is an instrument that graphically displays electrical signals and shows how those signals change over time. It measures these signals by connecting with a sensor。 It is composed of a tube amplifier, a scanning oscillator, a cathode ray tube, and so on. According to the difference of the signal, it can be divided into an analog oscilloscope and digital oscilloscope. According to the structure and performance, it can be divided into the ordinary oscilloscope, multi-purpose oscilloscope, multi-line oscilloscope, multi-trace oscilloscope, sampling oscilloscope, memory oscilloscope, digital oscilloscope. The oscilloscope is very versatile. It can be used to measure the shape of alternating current or pulse current waves. In addition to observing the waveform of the current, it can also measure the frequency, voltage intensity, etc. Any periodic physical process that can become an electrical effect can be observed with an oscilloscope.
1-screen display area; 2-multi-function knob; 3-common function area; 4-stop/run; 5-automatic setting; 6-trigger control system; 7-horizontal control system; 8-vertical channel control area; 9- Compensation signal output terminal/ground terminal; 10-analog channel and external trigger input terminal; 11-USB Host port; 12-menu soft key; 13-Menu on/off soft key; 14-power soft switch.
(1). Handle, pull up the handle vertically to easily carry the oscilloscope. When you don’t need it, just tap it down;
(2). Lock hole, you can use a safety lock to lock the oscilloscope in a fixed position through the lock hole;
(3). LAN interface, connect the oscilloscope to the network through this interface, and remotely control it;
(4). Pass/Fail or Trig Out output. When the oscilloscope generates a trigger, it can output a signal reflecting the current capture rate of the oscilloscope or output a Pass/Fail detection pulse through this interface;
(5). USB Device, this interface can be connected to a PC, and the oscilloscope can be controlled through the upper computer software.
(1). Press the "ROLL" key to enter the fast scroll mode, the time base range of the scroll mode is 50ms/div-100s/div;
(2). Horizontal Position, modify the trigger displacement;
(3). Horizontal gear, modify the horizontal time base gear.
(1). "1" analog input channel;
(2). Vertical "Position", modify the vertical displacement of the corresponding channel waveform;
(3). Vertical voltage gear, change the vertical gear of the current channel;
(4). "Math" Press this key to open the waveform calculation menu;
(5). "Ret" Press this key to turn on the waveform reference function.
(1). Press the "Setup" key to open the trigger function menu;
(2). Press the "Auto" key to switch the trigger mode to AUTO (automatic) mode;
(3). Press the "Normal" key to switch the trigger mode to Normal mode;
(4). Press the "Single" key to switch the trigger mode to Single (single) mode;
(5). Trigger level Level, set the trigger level.
(1). Press the "Auto Setup" button to turn on the waveform automatic display function;
(2). Press the "Run/Stop" key to set the operating status of the oscilloscope to "Run" or "Stop".
(1). First connect the probe, one end of the probe is connected to the signal under test, and the alligator clip is connected to the signal ground. Most oscilloscopes can quickly and automatically obtain waveforms through the Auto setup button of the oscilloscope. This is a convenient way and is very convenient for beginners.
(2). In addition to automatically acquiring the waveform, we also need to master the manual adjustment method. SDS1000X-E has a wealth of trigger types. We take the rising edge trigger as an example, select the appropriate gear, and adjust the vertical gear and time base gear. Adjust the size of the waveform in the vertical and horizontal directions. The Position knob can adjust the position of the waveform in the vertical and horizontal directions on the screen. You need to adjust the position of the level within the waveform range. The waveform that meets this trigger level will be displayed stably. On the oscilloscope screen.
The user can save the current settings, waveforms, screen images, and CSV files of the oscilloscope to the internal memory or an external USB storage device (such as a USB flash drive), and recall the saved settings or waveforms when needed. The front panel of this oscilloscope provides a USB Host interface for connecting a USB flash drive for external storage. Click to add text.
1. Let the oscilloscope work from a known state, turn off unused channels and unnecessary measurement, calculation, and analysis functions. For example, call the default setup (Default Setup), or call a saved setup file.
2. In the program-controlled environment, send the command "DISP OFF" to turn off the waveform display, and the oscilloscope can continue to trigger, read the waveform data or automatically save the waveform to the local hard disk.
3. It is usually the most time-consuming operation to transfer the waveform collected by the oscilloscope to the computer. Try to use the measurement, calculation, and XDEV function of the oscilloscope (the oscilloscope is embedded with a user-defined signal processing program) to process the waveform. The computer only needs to read Take the processed result.
4. If you need the computer to continuously read the not too long waveforms, you can make the oscilloscope work in the sequence mode (Sequence mode), so that several segments are continuously collected and then transmitted to the computer together. You can also make the oscilloscope work in a state where the waveform is automatically saved, and the waveform is saved on the local hard disk every time it is triggered. After the acquisition, the computer transmits the waveform files in batches.
5. If possible, let the program control software run directly in the operating system of the oscilloscope, which can greatly reduce the waveform transmission time.
6. If you need the oscilloscope to do a lot of measurements, calculations, and analysis, set the oscilloscope to "OpTImize analysis" (menu UTIliTIes "Preference Setup...).
7. If you need the oscilloscope to acquire a waveform and the computer to read the measurement parameters once, you can set the Trend function to record the measurement parameters. After the acquisition is completed, the computer reads all the measured values recorded by the trend function at one time.
8. Before the automatic test officially starts, set the oscilloscope to the vertical scale and sampling rate to be used in turn (it is recommended to work in the fixed sampling rate mode) so that the internal automatic calibration function can work in advance and can be reduced in the subsequent automatic test process. Frequency of small automatic calibration.
9. If the ambient temperature does not change significantly, send the command "AUTO_CALIBRATE OFF" to close the temperature calibration function
For hardware engineers, the standard configuration of their workbench is to have an oscilloscope, standard probes, a multimeter, signal source, and every instrument can work normally. When using an oscilloscope, each engineer’s test requirements are different, and the models they choose are also different. So how to quickly choose an oscilloscope that meets the test requirements? Rose shares ten steps to help you quickly select the model.
1. Understand the signal you need to test
What is the typical performance of the signal you want to capture and observe?
Does your signal have complex characteristics?
Is your signal a repetitive signal or a single signal?
What is the bandwidth or rise time of the signal transition you want to measure?
What signal characteristics do you plan to use to trigger short pulses, pulse widths, narrow pulses, etc.?
How many signals do you plan to display at the same time?
How do you deal with the test signal?
2. Bandwidth> 5 × the maximum frequency of the input signal
Oscilloscope bandwidth refers to the frequency at which the amplitude of the sine wave input signal is attenuated to -3dB, which is 70.7% of the true amplitude of the signal. Bandwidth determines the basic measurement capability of the oscilloscope for signals, and it is also a key determinant of price. When selecting the bandwidth, the rule of five can be used, that is, the oscilloscope bandwidth ≥ 5 X the maximum frequency of the input signal. If the oscilloscope does not have enough bandwidth, it will not be able to test high-frequency signals, the amplitude will be distorted, the edges will disappear, and the detailed data will be lost.
Three, the appropriate number of channels
The digital oscilloscope samples analog channels, stores, and displays data. Generally speaking, the more channels, the better, but adding channels will also raise the price. The more time-related analog and digital channels that an oscilloscope has, the more points can be measured simultaneously in the circuit, and the easier it is to decode in a parallel bus.
4. Sampling rate> 5 × (the highest frequency component)
The unit is the number of samples per second (S/s), which refers to the frequency at which the digital oscilloscope samples the signal. The faster the sampling speed of the oscilloscope, the higher the resolution, the better the displayed waveform details, and the less likely that key information or events will be lost. The sampling rate of the oscilloscope is at least four times the bandwidth of the oscilloscope, or at least 5 times oversampling to ensure the capture of signal details and avoid false signals.
5. Storage depth = sampling rate × display time
The memory depth is the number of samples that the oscilloscope can digitize and store in one acquisition. The deeper the oscilloscope's memory, the more time it can capture at the full sampling rate. The required memory depth depends on the number of displays you want to view and the sampling rate you want to maintain. If you want to view a longer period of time with a higher resolution between different points, you need to use a deep memory: storage depth = sampling rate × display time. After determining the memory depth, it is also important to examine how the oscilloscope operates when using the deepest memory setting.
6. Display function
The display performance of the oscilloscope depends to a large extent on the digital processing algorithm, rather than the physical characteristics of the display device. There is no good way to determine which oscilloscope is most suitable for the user's laboratory environment by studying the technical indicators of the oscilloscope. Only when the user's waveform is demonstrated and used in real-time on the user's workbench, can it be determined which oscilloscope is most suitable to meet the user's needs. The current digital oscilloscopes are divided into two categories: waveform viewing instruments and waveform analyzers [YD1]. Oscilloscopes designed for viewing waveforms are often used in testing and problem diagnosis applications. In these applications, the waveform image will provide all the information users need.
7. Trigger function
Most users who use oscilloscopes only use edge triggering, but in some applications, other triggering functions may be required. The advanced trigger function can isolate the event that you want to view. At the same time, advanced trigger options can also save a lot of time in daily debugging tasks. What if you need to capture rare events? Glitch trigger allows to trigger a positive or negative glitch, or trigger a pulse larger or smaller than the specified width. When diagnosing a problem, you can trigger the problem and look back at the root cause of the problem.
When the probe is installed, it becomes a part of the entire test circuit. As a result, the probe will cause resistive, capacitive, and inductive loads, making the oscilloscope show different measurement results from the object under test. Therefore, it is equipped with corresponding probes for different applications, and then choose one of them to minimize the load effect and get the most accurate reproduction of the signal. Choose the right probe:
Passive probe: economical in price, easy to use, and provides a wide range of measurement functions;
Active high-frequency probe: Active probe provides perfect versatility and accuracy when measuring high-frequency signals in current complex circuits;
Differential probe: Provides the highest CMRR, a wide frequency range, and the smallest time offset between inputs. It is the best choice for accurately measuring differential signals; Single-ended high voltage probe: The high voltage measurement solution expands the oscilloscope's ability to safely and accurately capture real-time signal information from elevated or floating voltage systems.
9. Analysis function
Automatic testing and built-in analysis functions can save users time and make work easier. Digital oscilloscopes usually have a series of measurement functions and analysis options that are not provided on analog oscilloscopes. Mathematical functions include addition, subtraction, multiplication, division, integration, and differentiation. Measurement statistics (minimum plant, maximum value and average value) can verify measurement uncertainty, which is an important resource when verifying noise and timing margin. Many digital oscilloscopes also provide the FFT function.
10. Seeing is believing, a trial is very important
The last one, if you have considered the first nine factors, you may have narrowed the scope to a small number of oscilloscopes that can meet the standard. Now you should use an oscilloscope for comparison, including ease of use and display response. If it is a mid-to-high-end oscilloscope, it is recommended that you apply for a prototype demonstration or trial first, so that it has a more intuitive effect, and then buy it.