Data acquisition
Using the formula in Equation 1 to solve for the equivalent referred-to-output total noise would result in as low as 1.12µVrms (OSR = 1024× at the lowest gain setting). Thus, higher dynamic range measurements signify low overall system noise. Similarly, parameters such as signal-to-noise ratio (SNR) and total harmonic distortion (THD) were acquired, with a –0.5dBFS sinusoidal signal applied at both inverting and non-inverting inputs of the device. First, SNR is defined as the ratio of the rms signal amplitude to the mean value of the root- sum-square (rss) of all other spectral components, excluding harmonics and DC. This can be further understood through Equation 2.
On the other hand, total harmonic distortion is defined as the ratio of the rms value of the fundamental signal to the mean value of the root-sum-square of its
Figure 10. Single-capture FFT, fully differential input, −0.5dBFS 1kHz sine.
harmonics (generally, only the first 5 harmonics are significant), as depicted in Equation 3.
Figure 7. Dynamic range.
Figures 8 and 9 show the respective SNR and THD values across various gain settings. The entire signal chain achieves a maximum SNR of 98dB and THD of –118dB. However, these parameters degrade at high input frequencies and high gain settings. An example FFT is likewise displayed in Figure 10. The isolated signal chain displays a flat noise floor at around 140dB below full scale and spurs buried below it. This denotes that the signal chain has good signal strength with a clean and comparable noise performance vs. its non-isolated equivalent.
Figure 8. SNR.
APPLICATIONS AND IMPACT The impact of an isolated precision signal chain spans across various industries and applications. In scientific research, it enables precise measurements in fields such as physics, chemistry, and biology, where accuracy and repeatability are paramount. In industrial automation, the signal chain ensures accurate process control, quality monitoring, and equipment diagnostics. In medical applications, it enables precise monitoring of physiological signals and accurate diagnosis. The impact also extends to areas such as environmental monitoring, energy management, and telecommunications, where reliable data acquisition is crucial for decision- making and optimisation.
FLOATING DAQ SYSTEMS Figure 9. THD. Instrumentation Monthly September 2025
Floating DAQ systems are best used for electronic test and measurement (ETM) applications. A common voltage measurement involves two reference points: high and low/zero potential (referred to as the earth ground). However, using
the earth ground as a reference creates risky high voltage measurements. Signals with high common- mode voltages are harmful to the individual components in the signal chain. This may result in damaging both the equipment and the data. High voltages also impose hazards on the person using the equipment. Moreover, noise, coupling, and interference introduced by ground loops also raise concerns for earth grounded systems. Floating DAQ addresses these risks by having a separate reference floating ground point. Floating measurements enable shorter paths to the point of acquisition, and, at the same time, allow the acquisition of signals with common-mode voltages. The different ground pins in the board can be observed in Figure 11.
CONCLUSION
An isolated precision signal chain has a profound impact on data acquisition: preserving accuracy, minimising noise and interference, and ensuring
data integrity. Incorporating precision amplification, isolation techniques, high resolution ADCs, and low-noise, low emission power management enables precise measurements, even in challenging environments. The impact of an isolated precision signal chain extends to various industries, enabling advancements in scientific research, industrial automation, healthcare, and beyond. As the demand for accurate and reliable data acquisition continues to rise, the significance of an isolated precision signal chain becomes increasingly evident in driving innovation and unlocking the full potential of data-driven applications.
Analog Devices
www.analog.com
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