The difference between digital oscilloscope and analog oscilloscope
The afterglow time of P31 fluorescent substance on CRT of ordinary analog oscilloscope is less than 1ms.In some cases, a CRT using P7 fluorescent material can give about 300ms of afterglow time. As long as there is a signal shining on the fluorescent material, the CRT will continuously display the signal waveform.When the signal is removed, the scanning trace on the CRT using P31 material rapidly darkens, while the scanning trace on the CRT using P7 material stays a little longer.
So what if the signal only happens a few times in a second, or if the signal only goes off in a few seconds, or even once?In this case, it is almost impossible to observe these signals using the analog oscilloscopes we have described above.
Digital storage is the storage of signals in the form of digital coding in an oscilloscope.After the signal enters the digital storage oscilloscope, or DSO, the oscilloscope will sample the signal voltage at a certain time interval before the signal reaches the deflection circuit of CRT. The sampled values are then transformed by an analog/digital converter (ADC) to generate binary words representing each sampled voltage.This process is called digitization.
The acquired binary values are stored in memory.The rate at which the input signal is sampled is called the sampling rate.The sampling rate is controlled by the sampling clock.For general usage, sampling rates range from 20 megabits per second (20 ms /s) to 200MS/s.The data stored in the memory is used to reconstruct the signal waveform on the oscilloscope screen. Therefore, the circuit between the input signal connector and the oscilloscope CRT in DSO is not only an analog circuit.The waveform of the input signal must be stored in memory before being displayed on the CRT. The waveform we see on the oscilloscope screen is always the waveform reconstructed by the collected data, rather than the direct waveform display of the added signal on the input connection end.