What is the storage depth of the oscilloscope, and how to set the selection

When we measure a signal, a large part of it may be useless information, and we don’t need to record it at all. But this piece of information will take up storage depth. The function of segmented storage is to help us remove the waveform segments that we don’t need to see, and only keep the waveform segments that we need to see, so as to maximize the use of memory depth. For specific operations, please refer to our previous article “Digital Oscilloscope Segmented Memory Function” The role and usage of “.

A friend repurchased an oscilloscope, but he said that the newly purchased oscilloscope had a problem. The reason was that the same signal he measured was very different from the previous oscilloscope, and the square wave distortion was more serious. The following figure shows the signal he measured with the newly purchased oscilloscope. It can be seen that the square wave has indeed become a trapezoid.

What is the storage depth of the oscilloscope, and how to set the selection

And the effect he measured with the old oscilloscope before is like this. It can be seen that the difference is really big, so is there really a problem with this repurchased oscilloscope?

What is the storage depth of the oscilloscope, and how to set the selection

We noticed that the current sampling rate of the oscilloscope in the first picture is 500KSa/s, while the current sampling rate of the oscilloscope in the second picture is 500MSa/s, which is a thousand times difference! Although the measured signal is the same signal, the measurement conditions are obviously different.

At this time, someone will ask, why is the sampling rate different for the same oscilloscope? When many newcomers choose an oscilloscope for the first time, they usually only pay attention to the bandwidth and sampling rate of the oscilloscope. Many oscilloscope manufacturers also put these two indicators at the forefront. There is nothing wrong with this, but many novices do not know that the oscilloscope The sampling rate of is not a fixed value, it will change with the setting of the storage depth and the change of the acquisition time. Our previous article “The Influence of Different Sampling Rates ON Waveforms-Oscilloscope Actual Measurement Case Analysis” also illustrates this point by way of actual case demonstrations.

What is the storage depth of the oscilloscope, and how to set the selection

Memory depth is a concept only available in digital oscilloscopes, and this parameter does not exist in analog oscilloscopes. The signal entering the digital oscilloscope passes through the front-end Amplifier and then the analog-to-digital converter. The collected signal is stored in the memory through the trigger system, and finally the data is processed and displayed on the Screen. In this process, the memory capacity is the physical medium that represents the storage depth of the digital oscilloscope.

Memory depth is also called record depth. The general indicator is 28Mpts, which means there are 28 million sampling points (pts=points).The storage depth, sampling rate, and waveform recording duration meet the following formula: sampling rate = storage depth ÷ waveform recording duration

It can be seen that if the oscilloscope wants to ensure that the sampling rate does not decrease under long time base recording, it must have sufficient storage depth. The sampling rate is also one of the important indicators to ensure that the signal is not distorted. So, when do you need a large storage depth? Obviously it is necessary to record a waveform for a long time, such as the measurement of power supply ripple and power supply noise, signal FFT analysis, spread spectrum clock analysis, etc., and the discovery of random or rare signals can also be solved with a long time base. .

So, is the greater the storage depth, the better? Obviously not. The oscilloscope’s memory depth selection has an automatic mode. In this mode, the oscilloscope will ensure that the sampling rate is sufficient, and try to select the smallest memory depth as far as possible. For example, when the oscilloscope records a 140ms waveform, the sampling rate must be 2GSa/s, then the storage depth must be 280M; but if only 14ms waveforms are recorded, then the 28M storage depth can meet the 2GSa/s sampling rate. At this time, even if we set the storage depth of 280M, the sampling rate will not change, because the maximum sampling rate of the oscilloscope is also fixed. The more waveform points the oscilloscope records, the greater the calculation pressure, which will affect the performance of the oscilloscope. The more obvious result is a decrease in the waveform capture rate. The automatic memory depth mode will find a balance between memory depth and operating performance. Point, try to ensure that the waveform is not distorted and does not affect the operating performance of the oscilloscope.

What is the storage depth of the oscilloscope, and how to set the selection

Therefore, when we choose an oscilloscope, we must also observe whether the operating performance of the oscilloscope at a large memory depth is still smooth and whether the acquisition is still real-time. I have encountered a more exaggerated oscilloscope. After the memory depth is increased, the oscilloscope will have to wait for 10 minutes or even half an hour to acquire a screen waveform, which is obviously not the result we expected.

Of course, the advantage of the large storage depth of the oscilloscope is that in addition to recording long-term waveforms, it can also cooperate with the segmented storage function to capture multiple waveform events at a sufficient sampling rate for effective analysis and help testers capture occasional signals and Save and Display the required data more optimally.

What is the storage depth of the oscilloscope, and how to set the selection

When we measure a signal, a large part of it may be useless information, and we don’t need to record it at all. But this piece of information will take up storage depth. The function of segmented storage is to help us remove the waveform segments that we don’t need to see, and only keep the waveform segments that we need to see, so as to maximize the use of memory depth. For specific operations, please refer to our previous article “Digital Oscilloscope Segmented Memory Function” The role and usage of “.

A friend repurchased an oscilloscope, but he said that the newly purchased oscilloscope had a problem. The reason was that the same signal he measured was very different from the previous oscilloscope, and the square wave distortion was more serious. The following figure shows the signal he measured with the newly purchased oscilloscope. It can be seen that the square wave has indeed become a trapezoid.

What is the storage depth of the oscilloscope, and how to set the selection

And the effect he measured with the old oscilloscope before is like this. It can be seen that the difference is really big, so is there really a problem with this repurchased oscilloscope?

What is the storage depth of the oscilloscope, and how to set the selection

We noticed that the current sampling rate of the oscilloscope in the first picture is 500KSa/s, while the current sampling rate of the oscilloscope in the second picture is 500MSa/s, which is a thousand times difference! Although the measured signal is the same signal, the measurement conditions are obviously different.

At this time, someone will ask, why is the sampling rate different for the same oscilloscope? When many newcomers choose an oscilloscope for the first time, they usually only pay attention to the bandwidth and sampling rate of the oscilloscope. Many oscilloscope manufacturers also put these two indicators at the forefront. There is nothing wrong with this, but many novices do not know that the oscilloscope The sampling rate of is not a fixed value, it will change with the setting of the storage depth and the change of the acquisition time. Our previous article “The Influence of Different Sampling Rates on Waveforms-Oscilloscope Actual Measurement Case Analysis” also illustrates this point by way of actual case demonstrations.

What is the storage depth of the oscilloscope, and how to set the selection

Memory depth is a concept only available in digital oscilloscopes, and this parameter does not exist in analog oscilloscopes. The signal entering the digital oscilloscope passes through the front-end amplifier and then the analog-to-digital converter. The collected signal is stored in the memory through the trigger system, and finally the data is processed and displayed on the screen. In this process, the memory capacity is the physical medium that represents the storage depth of the digital oscilloscope.

Memory depth is also called record depth. The general indicator is 28Mpts, which means there are 28 million sampling points (pts=points).The storage depth, sampling rate, and waveform recording duration meet the following formula: sampling rate = storage depth ÷ waveform recording duration

It can be seen that if the oscilloscope wants to ensure that the sampling rate does not decrease under long time base recording, it must have sufficient storage depth. The sampling rate is also one of the important indicators to ensure that the signal is not distorted. So, when do you need a large storage depth? Obviously it is necessary to record a waveform for a long time, such as the measurement of power supply ripple and power supply noise, signal FFT analysis, spread spectrum clock analysis, etc., and the discovery of random or rare signals can also be solved with a long time base. .

So, is the greater the storage depth, the better? Obviously not. The oscilloscope’s memory depth selection has an automatic mode. In this mode, the oscilloscope will ensure that the sampling rate is sufficient, and try to select the smallest memory depth as far as possible. For example, when the oscilloscope records a 140ms waveform, the sampling rate must be 2GSa/s, then the storage depth must be 280M; but if only 14ms waveforms are recorded, then the 28M storage depth can meet the 2GSa/s sampling rate. At this time, even if we set the storage depth of 280M, the sampling rate will not change, because the maximum sampling rate of the oscilloscope is also fixed. The more waveform points the oscilloscope records, the greater the calculation pressure, which will affect the performance of the oscilloscope. The more obvious result is a decrease in the waveform capture rate. The automatic memory depth mode will find a balance between memory depth and operating performance. Point, try to ensure that the waveform is not distorted and does not affect the operating performance of the oscilloscope.

What is the storage depth of the oscilloscope, and how to set the selection

Therefore, when we choose an oscilloscope, we must also observe whether the operating performance of the oscilloscope at a large memory depth is still smooth and whether the acquisition is still real-time. I have encountered a more exaggerated oscilloscope. After the memory depth is increased, the oscilloscope will have to wait for 10 minutes or even half an hour to acquire a screen waveform, which is obviously not the result we expected.

Of course, the advantage of the large storage depth of the oscilloscope is that in addition to recording long-term waveforms, it can also cooperate with the segmented storage function to capture multiple waveform events at a sufficient sampling rate for effective analysis and help testers capture occasional signals and Save and display the required data more optimally.

What is the storage depth of the oscilloscope, and how to set the selection

When we measure a signal, a large part of it may be useless information, and we don’t need to record it at all. But this piece of information will take up storage depth. The function of segmented storage is to help us remove the waveform segments that we don’t need to see, and only keep the waveform segments that we need to see, so as to maximize the use of memory depth. For specific operations, please refer to our previous article “Digital Oscilloscope Segmented Memory Function” The role and usage of “.

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