What does the ch value in the lower left corner of xy oscilloscope mean?

Oscilloscope, like other instruments (such as multimeter, etc. ), must be calibrated before use. The so-called calibration of oscilloscope is to debug the original waveform of oscilloscope correctly before testing. In other words, the corrected waveform should be consistent with the parameters set by the oscilloscope itself (these parameters are usually marked at the calibration test point). Take GW GOS-602 oscilloscope as an example (left): In the lower left corner of its panel are the parameters that need waveform correction, such as voltage value of 2V and frequency of 1KHz (right). The oscilloscope is required to correct waveforms (sine wave, cosine wave and square wave) with a peak-to-peak voltage of 2V and a frequency of 1KHz. However, oscilloscopes usually can't directly display the frequency of waveforms. Instead, they convert the frequency into a period (T= 1/f) according to the conversion between frequency and period, and then use a periodic wave to represent the frequency (the equivalent period of frequency 1KHz is 65440).

In the process of correcting the waveform, in order to facilitate the observation of the waveform, the center position of the waveform should be adjusted first, that is to say, the switch connecting the modal signals between inputs should be set at GND position (lower left). At this time, if the power supply is turned on normally, a horizontal bright line should be displayed. If it is not displayed, it is necessary to adjust the position, DC Bart and Inter Milan are up and down. In which, POSITION is the waveform up-and-down adjustment button (middle picture), DC BAL is the center adjustment of the horizontal bright line, and INTER is the brightness level. If the bright line is unbalanced (relative to the X axis), use a non-inductive screwdriver to adjust the rotation of TEACE near the focus (bottom right), and then adjust the convergence to the best state by adjusting the focus.