Previously, an article mentioned "Why oscilloscope manufacturers never mention refresh rate", and described the market status of oscilloscope manufacturers in the market on refresh rate parameters. Many oscilloscope users are concerned about the refresh rate indicator of the oscilloscope. Recently, when our FAE communicates with customers, many customers are interested in the high refresh rate of the ZDS2022 oscilloscope with 330,000 frames per second. What is the high refresh rate? What did you do?
What is the waveform refresh rate?
The waveform refresh rate, also known as the waveform capture rate, refers to the number of waveform refreshes per second, expressed as the number of waveforms per second (wfms/s).
In fact, the process of the oscilloscope displaying the signal waveform from the acquisition signal to the screen is composed of several capture cycles. A capture cycle includes the sampling time and the dead time. The analog signal is converted to a digital signal by the ADC sampling quantization. The time of the entire sample storage process is called the sampling time. The oscilloscope must perform processing such as measurement and display on the stored data to start the next sampling. This time is called the dead time. During the dead time, the oscilloscope did not perform waveform acquisition. A capture cycle completes and enters the next capture cycle.
The reciprocal of the capture period is the waveform refresh rate, as shown in Figure 1.1. The waveform refresh rate is 1/(Tacq+Tdeat).
The sampling time and dead time are shown in Figure 1.1. The waveform refresh rate is the reciprocal of Tacq (sampling time) and Tdeat (dead time). The sampling time is determined by the sampling pane of the oscilloscope screen and multiplied by the horizontal time base. In the horizontal direction, the sampling time will be fixed when the horizontal time base is determined.
The dead time is determined by the processing capability of the oscilloscope. When the oscilloscope has insufficient data processing capability, the collected big data cannot be processed in time. The dead time will be longer and the refresh rate will be reduced; when the oscilloscope When the processing power of data is very strong, the dead time will be shorter and the corresponding refresh rate will be high. Therefore, the dead time is an important factor affecting the refresh rate.
Increased trigger hold-off time The trigger hold-off time is equivalent to an increase in dead time in disguise, because during the hold-off period, the trigger circuit is closed and the trigger function is suspended. Even if a signal waveform that satisfies the trigger condition is not triggered, the oscilloscope will not trigger. Affects the refresh rate. However, triggering holdoff time does not mean dead time.
When triggering a waveform with a large period of repetition, since there are many waveform points in the waveform that meet the trigger conditions, the trigger waveform is unstable. In order to obtain a stable trigger waveform, we can set the trigger holdoff time so that the waveform is always the same. A point trigger, stable display trigger waveform. As in Figure 1.2, the holdoff time can be set to a value >200ns but < 600ns.
How does the dead time, which has a significant effect on the refresh rate, be calculated?
When capturing an abnormal pulse with a pulse width of 40 ns to 60 ns, the appropriate horizontal time base can be set at 50 ns/div. At this time, the ZDS2022 oscilloscope has a waveform refresh rate of 330,000 frames per second, which means that each sample is triggered. The total captured time T = 1s/330KHz = 3.03us, the effective sampling time is 50ns/divX14 (the ZDS2022 oscilloscope has 14 squares in the horizontal direction) = 700ns. The percentage of dead time is then (3030-700)/3030 = 76.89%.
Capture the same abnormal pulse. If the T oscilloscope has a refresh rate of 50K frames/second under the same time base, it means that the total time occupied by each trigger sampling is T=1S/50KHz=20us. The sampling time is 50ns/divX10 (the oscilloscope has 10 squares in the horizontal direction) = 500ns, then the percentage of dead time is (20000-500)/20000 = 97.5%.
The longer the dead time, the lower the probability of catching the sporadic signal. When the small probability abnormal waveform appears in the dead time, the oscilloscope will not capture the anomaly, which will have a great impact on the debugging of the signal.
How can the ZDS2022 oscilloscope achieve high refresh rates. So why does the ZDS2022 oscilloscope achieve refresh rates of up to 330,000 frames per second? The dead time is as low as 76.89%, which is 21.13% lower than the normal oscilloscope 97.5% dead time!
The ZDS2022 oscilloscope adopts ultra-large-scale FPGA integrated waveform memory, high bus bandwidth, greatly reducing data processing time, and adopting multi-thread parallel processing.
The waveform synthesis of the ZDS2022 oscilloscope is all processed using an optimization algorithm.
Summarizing the refresh rate of the oscilloscope directly determines the ability to capture abnormal glitches. Only by truly grasping the nature of the refresh rate, can we correctly understand the oscilloscope refresh rate index. The ZDS2022 oscilloscope has a refresh rate of 330,000 frames per second and can quickly capture waveform anomalies. , efficient and practical!
Say no more, not as much as you personally test!
What is the waveform refresh rate?
The waveform refresh rate, also known as the waveform capture rate, refers to the number of waveform refreshes per second, expressed as the number of waveforms per second (wfms/s).
In fact, the process of the oscilloscope displaying the signal waveform from the acquisition signal to the screen is composed of several capture cycles. A capture cycle includes the sampling time and the dead time. The analog signal is converted to a digital signal by the ADC sampling quantization. The time of the entire sample storage process is called the sampling time. The oscilloscope must perform processing such as measurement and display on the stored data to start the next sampling. This time is called the dead time. During the dead time, the oscilloscope did not perform waveform acquisition. A capture cycle completes and enters the next capture cycle.
The reciprocal of the capture period is the waveform refresh rate, as shown in Figure 1.1. The waveform refresh rate is 1/(Tacq+Tdeat).
Figure 1.1 Oscilloscope sampling process
What are the factors that affect the waveform refresh rate? The sampling time and dead time are shown in Figure 1.1. The waveform refresh rate is the reciprocal of Tacq (sampling time) and Tdeat (dead time). The sampling time is determined by the sampling pane of the oscilloscope screen and multiplied by the horizontal time base. In the horizontal direction, the sampling time will be fixed when the horizontal time base is determined.
The dead time is determined by the processing capability of the oscilloscope. When the oscilloscope has insufficient data processing capability, the collected big data cannot be processed in time. The dead time will be longer and the refresh rate will be reduced; when the oscilloscope When the processing power of data is very strong, the dead time will be shorter and the corresponding refresh rate will be high. Therefore, the dead time is an important factor affecting the refresh rate.
Increased trigger hold-off time The trigger hold-off time is equivalent to an increase in dead time in disguise, because during the hold-off period, the trigger circuit is closed and the trigger function is suspended. Even if a signal waveform that satisfies the trigger condition is not triggered, the oscilloscope will not trigger. Affects the refresh rate. However, triggering holdoff time does not mean dead time.
When triggering a waveform with a large period of repetition, since there are many waveform points in the waveform that meet the trigger conditions, the trigger waveform is unstable. In order to obtain a stable trigger waveform, we can set the trigger holdoff time so that the waveform is always the same. A point trigger, stable display trigger waveform. As in Figure 1.2, the holdoff time can be set to a value >200ns but < 600ns.
Figure 1.2 trigger release time
How to calculate the dead time? How does the dead time, which has a significant effect on the refresh rate, be calculated?
When capturing an abnormal pulse with a pulse width of 40 ns to 60 ns, the appropriate horizontal time base can be set at 50 ns/div. At this time, the ZDS2022 oscilloscope has a waveform refresh rate of 330,000 frames per second, which means that each sample is triggered. The total captured time T = 1s/330KHz = 3.03us, the effective sampling time is 50ns/divX14 (the ZDS2022 oscilloscope has 14 squares in the horizontal direction) = 700ns. The percentage of dead time is then (3030-700)/3030 = 76.89%.
Capture the same abnormal pulse. If the T oscilloscope has a refresh rate of 50K frames/second under the same time base, it means that the total time occupied by each trigger sampling is T=1S/50KHz=20us. The sampling time is 50ns/divX10 (the oscilloscope has 10 squares in the horizontal direction) = 500ns, then the percentage of dead time is (20000-500)/20000 = 97.5%.
The longer the dead time, the lower the probability of catching the sporadic signal. When the small probability abnormal waveform appears in the dead time, the oscilloscope will not capture the anomaly, which will have a great impact on the debugging of the signal.
How can the ZDS2022 oscilloscope achieve high refresh rates. So why does the ZDS2022 oscilloscope achieve refresh rates of up to 330,000 frames per second? The dead time is as low as 76.89%, which is 21.13% lower than the normal oscilloscope 97.5% dead time!
Figure 1.3 waveform synthesizer block diagram
ZDS2022 oscilloscope adopts ultra-large-scale FPGA for waveform synthesis, and all hardware acceleration processing; The ZDS2022 oscilloscope adopts ultra-large-scale FPGA integrated waveform memory, high bus bandwidth, greatly reducing data processing time, and adopting multi-thread parallel processing.
The waveform synthesis of the ZDS2022 oscilloscope is all processed using an optimization algorithm.
Summarizing the refresh rate of the oscilloscope directly determines the ability to capture abnormal glitches. Only by truly grasping the nature of the refresh rate, can we correctly understand the oscilloscope refresh rate index. The ZDS2022 oscilloscope has a refresh rate of 330,000 frames per second and can quickly capture waveform anomalies. , efficient and practical!
Say no more, not as much as you personally test!
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