Deep memory provides sustained high sample rates

Besides bandwidth, one of the most fundamental specifications in a digital storage oscilloscope (DSO) is its specified maximum sample rate. However, a DSO's sample rate is actually based on the scope's time base setting. At the faster time base settings, all oscilloscopes will capture waveforms using their specified maximum sample rates. But as you adjust the time base setting to slower ranges in order to capture longer waveforms, all scopes will automatically reduce their sample rates because of their limited memory depths. Deeper memory in an oscilloscope means that the scope can sustain its maximum sample rate on more time base settings enabling you to see more details of your signals.

These images show an example where MegaZoom III deep memory enables you to see subtle details of a complex signal. In the top image, you can see several cycles of a PWM (pulse-width modulated) signal. Notice the bright spots near the center of each burst. The lower photo shows a zoomed-in display on just one of the bright spots to reveal a runt pulse. With up to 8 Mpts of MegaZoom III acquisition memory, Agilent's 6000 Series oscilloscope is able to sustain its maximum sample rate in order to show us this signal anomaly.

With Agilent's MegaZoom III technology, the 6000 Series oscilloscopes provide the highest-definition display of oscilloscope waveforms in the industry, even exceeding the quality of traditional analog scopes. This is achieved by mapping up to 8,000,000 digitized points to a color XGA display (768x1024) with 256 levels of intensity grading.

Display intensity gradation can be extremely important when you are looking for signal anomalies, especially when you are viewing complex-modulated analog signals such as video, read-write disk head signals, and digitally controlled motor drive signals. Intensity gradation is also helpful in a wide variety of mixed-signal applications found in embedded microprocessor and microcontroller technologies common in the automotive, industrial, and consumer markets. But even when you are viewing purely digital waveforms, intensity gradation can show statistical information about edge jitter, vertical noise, and the relative occurrence of anomalies.

These two images show an example of capturing and displaying a composite video waveform (top photo) and a start-up cycle of a motor drive signal (bottom photo).

With Agilent's MegaZoom III technology, the 6000 Series oscilloscopes provide the fastest waveform update rates in the industry, without compromise. These scopes can produce up to 100,000 real-time waveforms per second, without the need to select special acquisition modes that may entail tradeoffs in oscilloscope performance and functionality.

Update rates in this range can be extremely important when you are trying to capture very infrequent events and signal anomalies such as dynamic jitter and random glitches. The image to the right shows an example of a high-speed signal that includes jitter (near left side of screen), vertical noise (top and bottom of waveform), and a very infrequent glitch (near center of screen). With fast waveform update rates, we can clearly see the dynamic nature of the jitter, which appears to be dominated by deterministic jitter (DJ). However, the biggest benefit of fast waveform update rates is this scope’s ability to easily capture the very infrequent glitch, which is actually a metastable state. This particular glitch only occurs approximately 1 time every 50,000 cycles of the input data signal that we are observing. With 100,000 real-time waveforms per second, we are able to see this glitch displayed on the scope’s screen multiple times a second.