Basic principle and measuring method of analytical oscilloscope
Oscilloscope is a widely used electronic measuring instrument. It can transform the invisible electric signal to the naked eye into the visible image, which is convenient for people to study the change process of various electric phenomena. A oscilloscope USES a narrow beam of high-speed electrons, struck on a surface coated with fluorescent material, to produce tiny points of light (this is how a traditional analog oscilloscope works). Under the action of the measured signal, the electron beam ACTS like the tip of a pen and can plot the instantaneous value of the measured signal on the screen. Use oscilloscope to be able to observe all sorts of different signal amplitude the waveform curve that changes with time, still can use it to test all sorts of different electric quantity, be like voltage, current, frequency, phase difference, amplitude modulation.
(1) Presetting: rotate the brightness knob counterclockwise to the bottom, move the vertical and horizontal position to the middle, and the attenuation is placed in the highest level, and the scanning is placed in the "outer X gear";
(2) Turn on the power again, and wait for one or two minutes after the light is on for preheating before carrying out relevant operations;
(3) First adjust the grayscale, then focus, and then adjust the horizontal and vertical displacement to make the highlights in the center of the appropriate area;
(4) Adjust scanning, scanning fine tuning and X gain, observe scanning;
(5) Unplug the outer X gear to the appropriate position in the scanning range file, and observe the voltage waveform in the vertical direction changing according to the law of sines and cosines provided by the machine;
(6) To study the external voltage from Y input and indirectly into the oscilloscope, adjust each gear to the appropriate position, you can observe the voltage waveform (and time changes of the image)(synchronous polarity switch can make the starting point of the image from the positive half cycle or negative half cycle start;
(7) If you want to observe the vertical offset of bright spot (such as when applied with a constant current voltage), you can adjust the scan to "outer X gear".
(different oscilloscopes may operate in different ways), etc.
(1) Insert the oscilloscope probe into the socket of channel 1, and put the attenuation on the probe into "1" gear;
(2) Put channel selection in CH1 and coupling mode in DC file;
(3) Insert the probe into the pinhole of the calibration signal source, and the light trace appears on the oscilloscope screen;
(4) Adjust the vertical knob and horizontal knob to stabilize the waveform displayed on the screen, and put the vertical fine-tuning and horizontal fine-tuning in the calibration position;
(5) The number of cells occupied by the waveform in the vertical direction is multiplied by the indicating value of the vertical attenuation knob to obtain the amplitude of the calibration signal.
(6) The number of bars occupied by each period of the waveform in the horizontal direction is multiplied by the indicating value of the horizontal scanning knob to obtain the period of the calibration signal (the inverse of the period is the frequency).
(7) In general, the frequency of the calibration signal is 1kHz and the amplitude is 0.5v, which is used to calibrate the internal scanning oscillator frequency of the oscilloscope. If it is abnormal, the corresponding potentiometer of the oscilloscope (internal) should be adjusted until it is consistent.
Under what circumstances should oscilloscope consider the sampling rate?
The bandwidth is dependent on the object under test. You want the minimum sampling interval (the inverse of the sampling rate) to capture the signal details you need, provided the bandwidth is satisfied. There are some empirical formulas about sampling rate in the industry, but basically they are all based on oscilloscope bandwidth, in practical application, it is best not to use oscilloscope to measure the same frequency signal. When selecting the type, the bandwidth of the oscilloscope should be more than 3 times that of the measured sinusoidal signal, and the sampling rate should be 4 to 5 times that of the bandwidth, which is actually 12 to 15 times that of the signal.For other waveforms, ensure that the sampling rate is sufficient to capture signal details. If you are using an oscilloscope, you can verify that the sampling rate is sufficient by stopping the waveform, amplifying the waveform, and if there is any change in the waveform (such as some amplitude), the sampling rate is insufficient, otherwise it will be ok. Point displays can also be used to analyze the adequacy of the sampling rate.
High precision dither test of digital oscilloscope
Jitter can be described as the periodic change of edge period or phase of adjacent pulse edge or even non-adjacent pulse edge. These indicators are suitable for measuring long-term and short-term clock and data stability.The data transmission performance of complex system is predicted by analyzing the jitter index and using the jitter test results.
Periodic jitter is used to measure edge - to - edge timing of clock or data cycle samples. For example, by measuring the time between the rising edges of 1,000 clock cycles, you can sample the statistical cycles that will tell you the quality of the signal.The standard deviation becomes RMS periodic jitter, the maximum period minus the minimum period, to get peak to peak period jitter.The precision of each measurement period determines the precision of jitter measurement.
Phase jitter is used to measure the time deviation between the edge of the measured signal and the edge of a reference signal so that any change in the signal phase can be detected.This indicator is different from periodic measurement in many ways. First, it USES each edge alone, without saying "period" or "cycle."Second, it can measure large time shifts.The edge phase can be deviated by hundreds or thousands of degrees, but can still be measured with very high precision (360 degrees equals one cycle or cycle time). The commonly used measure of phase error is the time interval error (TIE), and the measurement results are expressed in seconds relative to degrees.TIE matches the signal edges to the reference edges, and sums up the differences between the edges.After comparing a large number of edges, a sample set can be provided for analysis.As with the above periodic measurements, the standard deviation becomes RMS TIE, the maximum time minus the minimum time to get peak to peak TIE and so on.