Agilent Technologies' three 600 MHz and 1 GHz Infiniium oscilloscopes incorporate Agilent's MegaZoom deep-memory technology, which addresses the frustrations of current deep-memory users over slow responsiveness and manual setups.
The Infiniium 54830B, 54831B and 54832B models all have automatic deep memory with instant response.
Applications and use
Deep memory is required to find details buried in complex signals, to discover anomalies in the absence of good triggering events, and to correlate high-speed digital control signals with slower analogue signals.
Typically, R&D engineers in the communications and computer industries need deep-memory scopes when working with communications baseband signals, serial I/O data streams, and a mixture of analogue and digital signals found in microcontroller, digital signal processor and embedded systems designs.
Engineers have explained how they make do with the traditional deep-memory technology of existing oscilloscopes.
Typically, they are unable to use complex triggering, so they resort to edge triggering on the signal, and autoscale to size the signals onto the display.
They then increase the time displayed on the scope to make their entire signal viewable. Finally, they stop any acquisition activities to zoom in and make measurements or search the data for problems.
Frustrations with deep memory
Often, the first frustration that users experience with deep memory occurs as they zoom in on their data and discover that the waveform has been under-sampled, resulting in either an aliased or incorrect rendering of the signal.
This happens when the default memory on the scope is insufficient and the resulting sample rate used to capture the data has been too slow.
The user must manually open a menu, decide how much memory is required for an adequate sample rate, set the memory depth and then reacquire the waveform. This is sometimes not possible since some waveforms occur only once.
When the waveform is re-acquired with the deeper memory and users zoom in on the waveform to search through the data, they find themselves dealing with a second frustration: the display response time slows dramatically as front panel control changes.
It takes seconds before the display updates with every zoom and with every position change as users search through the captured data. Understandably, this poor response time has discouraged the use of deep memory on first-generation deep-memory oscilloscopes.
Traditional deep memory
User frustrations can be attributed to how traditional deep-memory oscilloscopes work. These instruments always set a predetermined, fixed-memory depth when the scope is autoscaled. The amount of memory never changes, and is preset by the manufacturer to an amount that generally will provide the user with a fast display update rate, but doesn't maximise the scope's sample rate.
When the user wants to view a longer time interval, the memory depth available does not change, so as the time interval is increased, the resolution - or sample rate - decreases. With traditional deep-memory oscilloscopes, users must manually increase the memory depth each time they work with complex signals because the default memory is usually insufficient to support the maximum sample rate required to accurately view and measure the signal. Also, the resolution is sometimes insufficient to capture fast events, which results in missed events.
A second problem with the traditional memory architecture is the responsiveness of the display with control changes.
Manufacturers set the memory depth to a fixed amount that is usually much less than the maximum available because the display responsiveness would be unacceptably slow when using the deepest memory.
When capturing a complex waveform with the deepest memory selected, these scopes can take up to eight seconds to respond to a control change.
This makes zooming into, and searching through, complex waveforms an extremely tedious task. Consequently, deep memory - a key and expensive feature - is relegated to a special mode and used only when needed the most.
MegaZoom deep memory
The Infiniium MegaZoom oscilloscopes use a deep-memory architecture designed to provide instant response to control changes, even with the deepest memories, and to always automatically set deep memory for maximum resolution.
Instant response to control changes means that the display updates as quickly with 16 M memory depths as with 50 K memory depths.
Users can quickly and easily zoom into, and then search through, long and complex signals without experiencing frustrating delays.
Deep memory can always be on during scope operation with no delays. With automatic deep memory, the maximum resolution is always available. Users need not stop what they are doing to calculate and manually set the memory.
When they select autoscale, MegaZoom begins to automatically calculate and set the memory depth. It then recalculates and resets the memory required for the maximum sample rate each time an engineer changes the horizontal scale (time/div) control.
When users need to view greater chunks of time, the system automatically adds memory to keep the maximum sample rate and resolution available.
It enables engineers to capture a waveform spanning a long time interval with the best resolution possible.
Hence, when they zoom into a signal, they see the true waveform, accurate measurements and the capture and display of fast events without using special modes or settings. This deep memory also addresses affordability, another important customer concern. Infiniium oscilloscopes come standard with 2 Mpts of MegaZoom deep memory on each channel, which is 20 times the depth of standard memory on some other deep memory scopes. Hence, users don't have to pay thousands of dollars for memory options to capture their signals.
Memory options of 4 M and 8 M on each channel allow users to extend the time window that can be captured by as much as 4 ms, at the maximum resolution of 4 GSa/s.
These options cost less than half that deep memory users have been paying. Obtaining the scope performance that an R&D engineer requires is now more affordable.
The heart of the MegaZoom deep memory architecture lies in a new proprietary custom application-specific integrated circuit (ASIC) that Agilent developed for its digital scope architecture.
To understand the full importance of this deep memory, it's useful to first consider the traditional deep-memory scope design.
Traditional architecture
With the older architecture, a single processor (scope CPU) is responsible for many tasks that are often performed sequentially.
In most cases, the processor has the primary responsibility of processing the samples from the front-end A/D to their storage in the acquisition memory, drawing the scope waveforms on the display, and monitoring front panel configuration changes.
The entire waveform record is then sent to the CPU, creating a serious bottleneck. This increases user frustration by slowing scope operation and missing important waveform anomalies due to a slow display update rate and a lot of dead time.
With the MegaZoom design, a custom acquisition and display system ASIC is connected to every input channel, and is responsible for fast analogue-like display updates.
The ASIC is able to capture up to 8 M points of data from the A/D at 2 GSa/s, or can be interleaved to double the sample rate to 4 GSa/s, capturing 16 M points of data. The ASIC contains a data processing engine for quickly reading the data from acquisition memory, and for processing it for display and measurement.
This greatly reduces the quantities of data transferred to the CPU, and also reduces any post-processing tasks.
The net result is that this memory substantially increases the waveform update rate and front panel responsiveness of these mid-range Infiniium scopes.
Continuing evolution
Enhancements are continually designed into the Infiniium oscilloscope family, and this latest series of mid-range instruments features a PC-based architecture with a new motherboard, a Pentium III 866 MHz processor and 256 MB RAM.
This non-proprietary architecture supports standard PC ports and devices, and offers remote connectivity, file-sharing capabilities and peripheral support.
Remote operation of test equipment has long been problematic, often requiring dedicated telephone lines and PCs running custom software and remote software packages. With the 54830B series - the first web-enabled deep memory oscilloscope - all that's necessary is access to the internet.
Web-enabled operation eliminates the need for special software, as well as any external computer connections to the oscilloscope.
Engineers can take advantage of the Infiniium's PC architecture by using the Windows 98 graphical user interface to assign the scope an IP address, and then connect the standard 10Base-T/100Base-T interface to their local area network.
Users can log onto the scope from a remote location by typing the IP address into any Java-enabled web browser.
Web-enabled operation allows engineers to sit at their desks and document reports by collecting screen shots from the scope in their laboratories or at remote sites. Up to three users can be logged onto an Infiniium scope at one time, enabling team members to simultaneously view and control the instrument, and to facilitate design and troubleshooting between various groups worldwide.
In addition to these web-enabled capabilities, the scope can use the internet with 'email on-trigger,' an action that sends an email with an attached screen shot to the user when a trigger occurs.
An engineer who receives an email from a scope while out of the office can use any web browser in a remote location to view and control a scope that is back on the laboratory benchtop.
The architecture also allows file and printer sharing on a user's LAN, and the use of external universal serial bus devices and peripherals, such as wireless trackballs and mice. Since the architecture is non-proprietary, users can take advantage of new features and peripherals as they become available.
When engineers decide to buy an oscilloscope, they usually look for a complete solution to match their unique measurement requirements. Infiniium offers a broad range of options and applications to help them efficiently do their jobs. These include:
- New low-mass high-performance active probes with a 1.5 to 4 GHz range, and a low cost, two-channel, 750 MHz probe;
- Differential probes from 200 MHz to 1 GHz;
- Wedge adapters for probing 3, 8 or 16 pins on quad flat packs (QFPs) and thin quad flat packs (TQFPs);
- A Logitech wireless trackball, wireless keyboard and mouse, for use when bench space is limited;
- A time-correlation fixture - another Agilent innovation - for deskewing, cross-triggering and importing scope waveforms and markers onto the 16700 logic analyser display.
