Introduction to the principles and functions of dual trace oscilloscopes
When the display mode switch is placed in the YA or YB position, the electronic switch is a monostable circuit. The preamplifier circuit YA or YB can work alone. At this time, the dual-trace oscilloscope can be used as an ordinary single-line oscilloscope.
When the display mode switch is placed in the YA+YB position, the electronic switch is inactive. At this time, the two channels YA and YB work at the same time, so the display of the addition of the two signals or the subtraction of the two signals can be obtained. However, whether the two signals are added or subtracted is selected through the polarity switch of the YA channel. This switch has two positions. In the first position, the graph on the fluorescent screen is the sum of the two signals; in the second position (-YA), the graph on the fluorescent screen is the difference between the two signals.
In order to observe the waveform of the measured signal changing with time, a linear scanning voltage (sawtooth wave voltage) must be applied to the horizontal deflection plate of the oscilloscope tube. This scan voltage is generated by the scan circuit. When a trigger signal is added to the trigger circuit, the scanning circuit is triggered, and the scanning circuit generates a corresponding scanning signal; when no trigger signal is added, the scanning circuit does not generate a scanning signal.
There are two types of triggers: internal trigger and external trigger, which are selected by the trigger selection switch. When the switch is placed in the inner position, the trigger signal comes from the measured signal sent through the Y-axis channel. When the switch is placed in the outer position, the trigger signal is sent from the outside. This signal should be in an integer ratio to the frequency of the signal being measured. In use, most oscilloscopes use internal triggering.
