Oscilloscope Channel Density

An important specification to consider when choosing an oscilloscope or digitizer is the numbers of channels the instrument has and its capacity to add more channels by synchronizing additional instruments. Your typical oscilloscope has two to four channels, each of which sample at a specific rate. Keep in mind that if your oscilloscope features time-interleaved sampling, which arranges multiple channels in alternating layers in order to boost the oscilloscope’s sample rate, and you are using all the channels at once, it may be impossible to reach the instrument’s maximum acquisition rate.

The number of channels you will need is determined by what applications you will be using the oscilloscope for. A traditional two- or four-channel oscilloscope is not always sufficient for certain applications, and there are two options for overcoming this limitation: the first, as you would expect, is to use an oscilloscope with a higher channel density; if you are cannot find an oscilloscope that suits your bandwidth, resolution, and speed requirements, you might consider using a platform that enables you to scale your test system by way of tighter synchronization and trigger/clock sharing.

Although synchronizing several boxed oscilloscopes over General Purpose Interface Bus (GPIB) or local area network (LAN) is nearly impossible as a result of high latency, finite throughput, and the necessity of external cabling, PCI eXtensions for Instrumentation (PXI) offers a noteworthy solution: an industry standard, PXI provides high-grade synchronization technology to extant high-speed buses including Peripheral Component Interconnect (PCI) and PCI Express.

Certain modular oscilloscopes and digitizers feature a technology known as T-Clock that provides incredible synchronization accuracy, which is to say tens of picoseconds. For example, when using T-Clock, you can build a thirty-four-channel, simultaneous, one giga-samples per second oscilloscope with NI PXI-5152 digitizers in an eighteen-slot chassis. In addition, you can synchronize multiple NI PXI-5105 digitizers in order to provide a system with one hundred thirty-six synchronized channels, each of which have twelve-bit resolution and run at sixty million samples per second. If you need an even higher count, PXI has timing modules for scaling multiple chassis up to five thousand channel-count systems.


George Leger has a Masters in Electrical Engineering from Stanford University, worked in private industry pioneering surface-mount technology and in government research labs for twenty years, published several papers on surface-mount technology, co-authored papers published in national symposiums on accelerator technology, was past president of SMTA and an adjunct professor at the community college level, holds a patent, and is a certified microchip design partner, serving as a consultant to many companies developing electronic circuits.

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