Description of the stability of oscilloscope waveform display
In order to make the graphics on the fluorescent screen stable, the frequency of the measured signal voltage should maintain an integer ratio relationship with the frequency of the sawtooth wave voltage, that is, a synchronous relationship. In order to achieve this, the frequency of the sawtooth wave voltage is required to be continuously adjustable in order to adapt to the observation of periodic signals of various frequencies. Secondly, due to the relative instability of the frequency of the measured signal and the frequency of the sawtooth wave oscillation signal, even if the frequency of the sawtooth wave voltage is temporarily adjusted to an integral multiple of the frequency of the measured signal, the graph cannot always remain stable. Therefore, oscilloscopes are equipped with synchronization devices. That is to say, a synchronization signal is added to a certain part of the sawtooth wave circuit to promote the synchronization of the scan. For simple oscilloscopes (such as the domestic SB-10 oscilloscope) that can only produce continuous scan (that is, generate a continuous sawtooth wave over and over). etc.), it is necessary to input a synchronization signal related to the frequency of the observed signal on its scanning circuit. When the frequency of the added synchronization signal is close to the autonomous oscillation frequency of the sawtooth wave frequency (or close to an integer multiple thereof), the sawtooth waveform can be Wave frequencies are "dragged into sync" or "locked". For oscilloscopes with the function of waiting for scanning (that is, no sawtooth wave is generated at ordinary times, and a sawtooth wave is generated for a scan when the signal under test arrives) (such as domestic ST-16 oscilloscope, SBT-5 synchronous oscilloscope, SR-8 type dual-trace oscilloscope, etc.), it is necessary to input a trigger signal related to the signal under test on its scanning circuit, so that the scanning process closely cooperates with the signal under test. In this way, as long as the appropriate synchronization signal or trigger signal is selected as needed, any process to be studied can be synchronized with the sawtooth wave scanning frequency.
