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The concept of vertical resolution: The first step in measuring analog signals with a digital oscilloscope is to convert the analog signal received by the probe into a digital signal using an ADC (Analog-to-Digital Converter). The resolution of this ADC chip directly determines the sampling accuracy in the vertical direction of the oscilloscope. For example, if the ADC is 8-bit, then the signal in the vertical direction can be divided into 256 segments, ranging from 00000000 to 11111111, which is 2 to the power of 8. The vertical resolution of the analog-to-digital converter is the same as that of the digital oscilloscope; it indicates the precision with which the oscilloscope converts the input voltage into digital values. What determines the vertical resolution displayed on a digital oscilloscope? In order of priority from highest to lowest: 1. The resolution of the front-end ADC; 2. The resolution of the display screen: it determines how much of the processed signal can be shown. For example, although an ADC can display 256 segments in the vertical direction, the resolution of the display screen in that direction might be only 240 pixels; as a result, some of those points are combined into 1 pixel for display. 3. Interpolation algorithm: On actual oscilloscopes, not all of the pixels displayed are generated by actual sampling; some are virtual points calculated using an interpolation algorithm. A good interpolation algorithm results in minimal differences between the interpolated points and the actual points. Vertical accuracy: When we use the same oscilloscope to measure the same signal at different vertical settings, the measurement results tend to vary. For example, when we measure a 2V square wave signal, the amplitude measured at a vertical setting of 2V might be 1.960V. https://pic1.zhimg.com/80/v2-c2ca68a39b3dc49b0d846b2499e4c084_720w.jpg At a vertical setting of 500mV, the amplitude measured was 1.980V. https://pic2.zhimg.com/80/v2-4fb1606003ba7c3657366ad7718f6989_720w.jpg Why is this happening? Since it involves the issue of vertical resolution, assuming that when the vertical scale is set at 500 mV/div, there are 10 divisions in the vertical direction, the vertical resolution is determined by the resolution of the ADC. This gives (500 mV * 10) / 256 = 19.531 mV; in other words, the ADC is unable to detect voltage signals smaller than 19.531 mV. When measuring the same signal with a vertical scaling of 2V/div, the voltage level that the ADC can resolve is (2000mV*10)/256 = 78.125mV; signals below this value cannot be measured. In other words, all digital measuring instruments have quantization errors in their data acquisition. The higher the number of bits in the ADC, the smaller these quantization errors become, but they can only be reduced to an infinite degree – they cannot be eliminated entirely. Therefore, when measuring waveforms, we try to ensure that the waveform fills the oscilloscope screen, with the aim of improving vertical accuracy and thus yielding more accurate measurement results. https://pic1.zhimg.com/80/v2-ee2f37c4fc842d5f21b600c24f94753c_720w.jpg The resolution can be improved by changing the algorithm. In digital oscilloscopes, the higher the number of bits in the ADC, the greater the vertical resolution; this resolution is determined by hardware and cannot be changed once it is set. However, the resolution resulting from the effective digits of the entire oscilloscope system is different from the former, and we can improve the resolution using software. https://pic2.zhimg.com/80/v2-9f6926ed3b6a2580a91e9f60a2a2d3fd_720w.jpg Currently, the most common method used by most oscilloscopes to increase resolution after ADC sampling is the “averaging” approach. https://pic4.zhimg.com/80/v2-9d71cf8afabbe680a900c9c0e22722d7_720w.jpg In the average sampling method, a number of averaging iterations N can be set first; thereafter, the oscilloscope aligns the N captured waveforms based on their trigger points and performs an averaging operation on them, resulting in a single averaged waveform. https://pic1.zhimg.com/80/v2-bad51e62c119a27c28699819256d313c_720w.jpg This sampling method reduces random noise without sacrificing bandwidth, thereby improving the resolution of the oscilloscope system. However, the average mode takes longer to respond to changing waveforms; it trades off the oscilloscope’s speed in order to achieve higher resolution. Moreover, due to its specific processing mechanism, it can only be used with periodic wave signals. In summary, the vertical resolution of an oscilloscope’s display is inherently limited. Additionally, when measuring high-frequency signals, the amplitude values are not accurate; at the upper frequency limit, there can be an error of up to 30%. Moreover, too high a vertical resolution increases the analog-to-digital conversion time, which in turn affects the sampling rate and thus the bandwidth, making it counterproductive. The vertical resolution of a standard oscilloscope is 8 bits, while that of high-resolution oscilloscopes reaches 12 bits. If the precision of the oscilloscope’s analog circuitry itself isn’t improved, it is meaningless to simply focus on the resolution of the ADC. If accuracy in voltage measurement is required, a multimeter should be used. The main function of an oscilloscope is to observe the shape of waveforms, and its measurement accuracy is generally within 2%; such accuracy is more than sufficient for the vast majority of applications.