Spectrum adds increased sensitivity option to digitizers

Hackensack, NJ. Spectrum Instrumentation Corp. has announced an option (M4i.22xx-ir40m) for its high-speed 22xx Series digitizer products that increases their sensitivity and therefore provides better absolute resolution for low amplitude signals in the ±40-mV to ±0.5-V range. The current products are optimized to acquire, store, and analyze signals from ±200 mV up to ±2.5 V.

Oliver Rovini, Spectrum’s CTO, said, “The modular way that we design and build our products means that we can provide this front-end option very easily as a new daughter board within the 22xx range. Matching the digitizer’s range to the signal under test is important as it ensures maximum dynamic range as well as better measurement accuracy and resolution.”

Rovini continued, “For example, if a signal only covers half of a digitizer’s selected full-scale range, then only half of the digitizer’s available analog-to-digital converter resolution is used. Smaller, or lower level, signals will use even less of the ADC’s capabilities and further reduce the digitizer’s overall signal-to-noise performance. This new option lets users select more sensitive, full-scale ranges so that, even for low-amplitude signals, the ADC’s complete dynamic range is available.”

He explained the example of a 10-bit digitizer with a lowest 50-Ω range at ±0.5-V full scale input range that has to acquire a signal with an amplitude of around 50 mV. The 10-bit ADC offers 1,024 (210) levels of resolution, each of about 1 mV (1V/1,024). The signal would therefore only cover about 50 levels of the 10-bit ADC’s available range.

Spectrum’s 22xx Series digitizers use 8-bit ADCs that give 256 (28) levels of resolution. So, by using this new low-range option, the digitizer becomes more sensitive with around 0.3 mV (80 mV/256) of resolution. This enables the 8-bit ADC to capture the 50-mV signal with around three times more resolution than the more expensive 10-bit unit.

For extremely low-amplitude signals, the 22xx Series digitizers can also be used with Spectrum’s high-bandwidth (up to 2 GHz) external SPA Series amplifiers. These free-standing units offer an additional x10 (20 dB) or x100 (40 dB) gain making it possible to capture and analyze signals that go down into the low mV ranges.

Spectrum’s 22xx Series digitizers come in a variety of popular form factors including PCIe, PXIe, and LXI. Models are available with sampling rates of 1.25, 2.5 and 5 GS/s and bandwidths of 500 MHz or 1.5 GHz (700 MHz with the low-input-range option). Versions with one, two, and four channels are available for units in the PCIe and PXIe formats, while the larger LXI-based instruments offer models that have from 2 to 24 fully synchronous channels.

All Spectrum digitizers are designed so that each channel features its own ADC, large acquisition memory (1 GS/channel), and independent, front-end, signal conditioning circuitry. The ADCs are clocked synchronously to ensure inter-channel timing measurements can be made with the best possible accuracy as well as maintaining a constant phase relationship. The combination of fast sampling rate, wide bandwidth, and long acquisition memory enables the digitizers to capture long, complex, high-frequency signals. It also makes it possible to characterize and measure fast events that go down into the nano- and sub-nanosecond timing ranges.

Advanced acquisition modes

Designed to acquire and analyze a wide range of signals, the digitizers also include a host of acquisition modes: Single Shot mode for capturing transient events, Multiple Recording for storing numerous signals that arrive in bursts or packets, Gated Sampling to synchronize the acquisition with another event, and ABA mode for mimicking the operation of a chart recorder and enabling segments with fast and slow sampling rates to be recorded simultaneously. All the acquisition modes can be used with FIFO streaming that allows acquired data to be continuously transferred to a host PC.

Each channel of the digitizer, as well as two external inputs, can act as a trigger source with the capability of combining all sources by AND/OR logic functions. The logic feature makes it possible to trigger only when specific patterns are seen on the inputs, simplifying complex trigger situations. Trigger events can also be date and time stamped to identify exactly when, and how often, they occurred.

Software support

The digitizers come with tools necessary to capture, digitize, and analyze electronic signals. The products are fully programmable and come with drivers that allow users to write their own control programs with a variety of popular programming languages, including C++, Visual Basic, VB.NET, C#, J#, Delphi, IVI, Java, and Python code. Third-party software support is also provided for LabVIEW, LabWindows, and MATLAB.

If users do not want to write their own programs, Spectrum offers SBench 6—an easy-to-use, graphical user interface. SBench 6 provides control all of the digitizer’s operating modes and settings. The software has a number of built-in features for waveform display, data analysis, and documentation. Acquired and analyzed waveforms can be stored and exported to other devices, or other software programs, in a number of formats such as MATLAB, ASCII, binary, and wave.

The 22xx Series digitizer products, together with the new M4i.22xx-ir40m front-end option, are available for immediate delivery. All units are shipped factory-tested and include a base version of Spectrum’s SBench 6 software, support drivers, a full SDK, and a two-year manufacturer’s warranty.

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