Basic principle and measuring method of oscilloscope
Oscilloscope is one kind of electrical measurement equipment with wide application. It could transfer invisible electrical signal to visible image to facilitate people research change processes of all kinds of electricity phenomenon. Oscilloscope use narrow electron beam which consists high-speed electronics and project onto screen coated with fluorescent substance to produce small spot (this is original working principle of analog oscilloscopes. Under the function of measured signal, electronics like the point of a pen which could on screen describe change curve of measured signal during instantaneous value. An oscilloscope can be used to observe the waveform curves of various signal amplitudes varying with time. It could also be used to measure various electricity, such as voltage, current, frequency, phase, amplitude modulation and etc.
(1) pre-adjusting: counterclockwise rotate the brightness button to the bottom, shift vertical and horizontal positions to the middle, set the attenuation gear at the highest level, place scan “outside X gear”
(2) turn on the power, do following steps waiting for one or two minutes after the indicator light is on
(3) adjust luminance first, then adjust the focus, adjust vertical and horizontal displacement to make the light point in center of suitable area.
(4) adjust scan, scan fine tuning and X gain, observe scan.
(5) adjust outside X gear to suitable scan range, observe the voltage waveform according to sine and cosines law on vertical direction inside the device.
(6) Connect the applied voltage to be studied to oscilloscope through Y input and earth. Adjust all gears to suitable position and observe waveform (the picture changes with time) (the synchronous polarity switch can make the starting point of the image start from positive half cycle or negative half cycle.)
(7) If you want to observe the vertical migration of light spot (with one added DC voltage), could adjust scan to “outside X gear”.
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.
The suspension ability of oscilloscope and the isolation ability between channels
For economical fault search application, usually need is double-channel oscillograph, however, the relationship of the requirements to observe several analog signals, will need a 4 channel oscilloscope, a lot of work in analog and digital two kinds of signal systems engineers can choose mixed signal oscilloscope (the oledata.mso), it will be logic analyzer channel count and triggered abilities associated with the comprehensive to have higher resolution time of oscilloscope display in a single instrument. If you measure three-phase electricity, thyristor and other active devices or lines, there is no absolute zero between the two ends, that is, the so-called floating signal, at this time from the safety and accuracy of operation, you should choose the isolated channel oscilloscope;If the timing and phase shift of multiple channels are compared, oscilloscopes with more than two channels should be selected, when the isolation between channels is more important.