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Feature Oscilloscopes Changing the way you test and debug


The latest technology in basic bench oscilloscopes will change the way you solve your measurement problems. This technology delivers value, functionality and flexibility by combining four instruments into one general purpose oscilloscope. Agilent Technologies explains


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scilloscopes are used as elec- tronic measurement instru- ments that monitor input signals and graphically display these signals on the oscilloscope in a voltage versus time format. They are critical for making measurements on a wide range of analogue and digital circuits and are the one tool used more than any other to test, verify and debug electronic designs. They are vital in determining which components of a system are behaving correctly and which are malfunctioning. They can also help you determine whether or not a newly designed component behaves the way you intended. Oscilloscopes are used in a wide range of fields including: universities, research laboratories, manufacturing lines and aerospace-defense industries.


What’s inside an oscilloscope? Common oscilloscope architectures like the one shown in Figure 1, is the architecture that Agilent (HP then) pio- neered in the early 90’s with the HP54600 series scopes and the same architecture that is used in any number of oscillo- scope products in the market- place today. While one can make an oscilloscope with more discrete functional blocks, performance is limited due to a variety of well know system integration issues such as heat, interconnect speeds, power dis- sipation and cost. To account for this, performance in a number of key areas can be compromised such as update rate, measurement throughput and scope unresponsiveness.


MegaZoom custom ASIC technology from Agilent uses an architecture that solves the compromised performance integration issues we see in the common architecture (see Figure 2). Notice several of the blocks have now been integrated on a custom ASIC chip. By integrating, Agilent can take advantage of higher performance internal busses, and enable a new architecture to emerge in their oscillo- scopes. Oscilloscopes that implement MegaZoom technology in their archi- tecture provide industry leading wave- form update rates and incredible signal


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increases performance while reducing cost. Now, more engineers and techni- cians have access to capabilities previously only available on much more expensive oscilloscope products, which will allow them to get their products to market more quickly and with a much higher reliability rate.


Update rate


visibility to the customer’s using them. This is possible because the integration places several key CPU and software functions in hardware rather than pro- cessing with software after the signals have been acquired. This allows for high performance for many common functions such as measurements, wave- form limit testing and serial decode. This increases performance directly for those modes while freeing up CPU bandwidth to more efficiently address remaining CPU tasks.


Whether you are an engineer, techni- cian or student, new functions and


Figure 2:


Block diagram of Agilent’s 3rd generation of MegaZoom III architecture, shows the integration of functionality into an ASIC chip


tasks get added to the current tasks you are asked to perform. Many times budget constraints and project sched- ules require solutions that will reduce test time. To meet the current and future needs, an oscilloscope needs to continue to add features that reduce test and debug times, while still being affordable. This is not an easy task for an oscilloscope architect. Still, not impossible for the technical expertise of Agilent’s custom ASIC designers. In Figure 3, the six blocks with white text are now all integrated into one custom ASIC chip. Now, all of the performance points have been improved yet again with more acceleration of functionality to preserve optimal operating ranges, productivity and increase insight. This very systematic inclusion of more oscil- loscope functionality onto one chip


Figure 3:


The MegaZoom technology architecture integrates even more functionality into the custom ASIC


Figure 1: A common oscilloscope architecture


If you are testing a device to analyse whether it is functioning correctly and you happen to probe a signal that had a ‘glitch’ wandering around on it, you’d want to see it so you could trace it to root cause and determine a fix. Oscilloscopes with faster update rate give you a much higher probability of capturing a glitch than those with slower update rate. This is due to the amount of ‘blind time’ an oscilloscope has. It is the amount of time it takes the oscilloscope to capture and display the signal. In architecture without MegaZoom technology, like that in Figure 1, the upper limits are up to 55,000 waveforms per second, but only in special modes. MegaZoom IV Custom ASIC technology as shown in Figure 3 can reach update rates of over one million waveforms per second. This translates into minimal blind time with this oscilloscope and gives you the highest probability of catching that infrequent glitch, the one that keeps you up at night worrying about and the one you do not want an end customer to find before you do.


In other cases, you just need to take a look at your signal and observe just how ‘good’ it is. Does it look right? Is it noisy? Is it stable? In an instant, you make the analysis in your mind, then a judgment, and then move on to the next signal. It’s in this mode where update rate is critically important. If your scope is rendering the signal informa- tion poorly – due to slow waveform update rate – then it’s blind to your input during a long portion of the time you are debugging. Using an oscillo- scope with MegaZoom technology will give you a much higher confidence


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