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.
The development of oscilloscope probe
In the past 50 years, the interface design of various oscilloscope probes has been evolving continuously to meet the requirements of increased instrument bandwidth speed and measurement performance. In the earliest days, banana plugs and UHF connectors were commonly used. In the 1960s, the common BNC connector became the common probe interface type because BNC was smaller and more frequent.
Later, some manufacturers put forward the common workarounds, BNC type probe interface design in the use of the BNC connector at the same time, additional provides a simulation code detection scale coefficients of stitching, as part of the mechanical and electrical interface design, which makes the oscilloscope is compatible with automatic detection and change the oscilloscope display of vertical attenuation range.
Requirements for oscilloscope current probe
Wide frequency range: from dc to tens or even hundreds of megabytes.
The range is large: from milliampere to kiloampere.
Small size: with the improvement of integration and the increase of signal frequency, the external size of components is getting smaller and shorter and pins are getting shorter and shorter. Easy operation and high accuracy.
Digital oscilloscope test accuracy
Any designer who chooses oscilloscope for parameter measurement will know its test accuracy through the product index to ensure enough tolerance error and measurement margin.Jitter testing is no exception. For example, the tekker TDS6804B oscilloscope indicates the precision and specifies the typical value of jitter measurement capability.Jitter measurement accuracy is affected by many factors, including timing stability of oscilloscope, sampling noise, instrument amplitude background noise and interpolation error.
Interpolation error is caused by linear interpolation between actual voltage samples.This error is less than 0.3ps RMS when measuring 100ps rise time signal and oscilloscope detects at 50% voltage threshold with 20GSa/s sampling rate.In many cases, this error can be improved by sine (X)/X sine interpolation in oscilloscope and other methods, such as making full use of the vertical dynamic range of oscilloscope, so that the input signal amplitude reaches the oscilloscope full scale.In most cases, the error for this reason is much smaller than for other error sources, and can be further reduced by using interpolation such as Sin(X)/X or Sinc.