Data acquisition
Figure 9. Source measurement unit simplified block diagram.
Figure 10. ADAQ4003 dynamic range, with SNR vs. the oversampling rate (OSR) for various input frequencies.
accommodate the increased number of channels in parallel. The ADAQ4003 offers breakthrough precision performance, reduces the end system component count, and allows for improved channel density amid board space constraints while easing their calibration burden and thermal challenges for these types of dc measurement scalable test instruments. The ADAQ4003’s high precision combined with fast sampling rate reduces noise, and no latency makes it ideal for control loop applications to provide an optimal step response and fast settling to improve test efficiency. The ADAQ4003 helps ease the design burden by eliminating buffers for distributing the
reference voltage on instruments due to their own drift and for board space constraints. In addition, the drift performance and aging determine the accuracy of a test instrument, so the deterministic drift of the ADAQ4003 reduces the cost of recalibration and the instrument’s downtime. The ADAQ4003 meets these requirements, pushes instruments’ capability to measure lower voltage and current ranges, and helps them to optimise their control loop for a variety of load conditions, which directly translate into an improvement in operating specifications, test efficiency, throughput, and cost for the instruments. The high test throughput and shorter test times of these instruments directly translate into a lower test cost for end users. The SMU high level block diagram is shown in Figure 9 and its corresponding signal chain is shown in Figure 5. The high throughput rate enables oversampling
of the ADAQ4003 to achieve the lowest rms noise and detect small amplitude signals over the wide bandwidth. Oversampling the ADAQ4003 by a factor of four provides one additional bit of resolution (this is only possible because the ADAQ4003 provides sufficient linearity—see Figure 8) or a 6 dB increase in dynamic range—in other words, the DR improvement due to this oversampling is defined as: ΔDR = 10 × log10 (OSR) in dB. The ADAQ4003 typical dynamic range is 100 dB at 2 MSPS for a 5 V reference
with its inputs shorted to ground. Therefore, when the ADAQ4003 is oversampled by a factor of 1024× at an output data rate of 1.953 kSPS, it offers an unbeatable dynamic range of ~130 dB for a gain of 0.454 and 0.9, which can precisely detect very small amplitude µV signals. Figure 10 shows the dynamic range and SNR of ADAQ4003 for various oversampling rates and input frequencies of 1 kHz and 10 kHz.
ConClusion
This article presented a few key aspects and technical challenges associated with designing precision data acquisition systems and how Analog Devices is leveraging its domain expertise in linear and converters to develop the highly differentiated ADAQ4003 signal chain µModule solution to solve some of the toughest engineering problems. The ADAQ4003 eases engineering burdens such as component selection and building production- ready prototypes, while enabling system designers to deliver distinguished system solutions to their end customers faster. The ADAQ4003 µModule device’s breakthrough precision performance combined with a small form factor adds greater value for a wide range of applications focused on precision data conversion for applications as diverse as automated test equipment (SMU, DPS), electronic test and measurement (impedance measurement), healthcare (vital sign monitoring, diagnostics, imaging) and aerospace (aviation), as well some industrial uses (machine automation input/output modules). µModule solutions such as the ADAQ4003 significantly reduce the total cost of ownership for system designers (as illustrated in Figure 11 in each of the areas) and reduce the PCB assembly cost, increase manufacturing support by improving lot-to-lot yield, enable design reuse for scalable/modular platforms, and simplify the calibration burden in their end application, while accelerating their TTM.
Figure 11. Reduction in total cost of ownership using signal chain µModule technology. Instrumentation Monthly May 2021 Analog Devices
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