The importance of deep memory in oscilloscopesFollow article
Acquisition memory depth, equals the number of samples that are stored with each acquisition. Memory depth, however, is specified in points (Mpoint) or samples (Msample).
What are the two key benefits of oscilloscopes with deep memory?
1. Capturing a longer period of time
Deep memory helps in instances where the cause and effect may be separated by a significant time period, and plays a key role in viewing events that simply take longer to transpire. You can determine acquisition time window using the following formula:
Acquisition time window = memory depth / sample rate
2. Retaining maximum bandwidth while capturing more time
As your oscilloscope acquires more time, more memory will be used to retain the maximum sample rate possible. As the amount of time captured increases, your oscilloscope will run out of additional memory. As a result, the oscilloscope begins reducing sample rate. Capturing twice as much time reduces the sample rate by a factor of two.
What is deep memory?
The oscilloscope’s memory depth is the maximum possible record length for one acquisition. Oscilloscopes with lower memory (screenshot 1) are forced to reduce sample rates sooner in order to capture more time. Thus, they have reduced bandwidths at slower time base. This can lead to insufficient sample rates to accurately slow signals.
However, deeper memory oscilloscopes (screenshot 2) retain full bandwidth. This means the scope can maintain maximum sample rate as the amount of captured time increases. A deep memory will provide more accurate and reliable measurements and users can be confident that no important signal events will be missed. Besides, they benefit from viewing longer periods of time and quickly finding signal anomalies or important events.
The following example illustrates the importance of memory depth: While the scope will capture 2 ms of time with 10 Msample memory and a sample rate of 5 Gsample/s (screenshot 3), it will capture 40 ms of time with the same sample rate of 5 Gsample/s and 200 Msample memory (screenshot 4).
What are benefits of maximum sample rates?
Typically, oscilloscopes are designed with a maximum sample rate to match the maximum analog bandwidth needed. When the sample rate is reduced, an undesirable consequence is that the sample rate may not be sufficient to accurately reconstruct the signals. This may lead to aliasing.
What is the relationship between sample rate, record length and acquisition time?