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Selection of Input Channel and Input Coupling for Oscilloscope
1. Selection of afferent channels
There are at least three ways to select the incoming channel: channel 1 (CH1), channel 2 (CH2), and dual channel (DUAL). When channel 1 is selected, the oscilloscope only displays the signal source of channel 1. When channel 2 is selected, the oscilloscope only displays the signal source of channel 2. When two channels are selected, the oscilloscope displays both channel 1 signal source and channel 2 signal source. When testing the signal source, the oscilloscope should be connected with the circuit under test. According to the selection of the incoming channel, the oscilloscope probe is inserted into the corresponding channel socket. The oscilloscope probe is connected with the circuit under test, and the oscilloscope probe contacts the measured point. There is a two-bit switch on the probe of the oscilloscope. When the switch is set to the position of'*1', the measured signal source is sent to the oscilloscope without attenuation. The voltage value read from the fluorescent screen is the actual voltage value of the signal source. When the switch is set to the position of'*10', the measured signal source attenuates to 1/10, which is then sent to the oscilloscope. The actual voltage value of the signal source is multiplied by 10 from the fluorescent screen.
2. Afferent coupling
There are three modes of afferent coupling: AC, GND and DC. When "ground" is selected, the scanning line shows the position of "oscilloscope ground" on the screen. DC coupling is used to measure the absolute value of DC signal source and to observe very low frequency signal source. AC coupling is used to observe AC and AC signal sources with DC components. In the digital circuit experiment, the "direct current" mode is usually used to observe the absolute voltage of the signal source.
trigger
The first section points out that after the input of the measured signal source from the Y axis, one part is sent to the Y axis deflection board of the oscilloscope, which drives the light point to move proportionally along the vertical direction on the fluorescent screen; the other part is diverted to the X axis deflection system to generate trigger pulses, trigger the scanning generator, and generate repeated sawtooth wave voltage to add to the X axis deflection board of the oscilloscope tube. On the other hand, the light point moves along the horizontal direction, and the two are in one. The figure depicted by the light point on the fluorescent screen is the figure of the signal source under test. Therefore, the correct triggering mode directly affects the effective operation of the oscilloscope. In order to get a stable and clear signal source waveform on the fluorescent screen, it is very important to master the basic triggering function and its operation method.