Feature: T&M


Figure 3: An 8-channel DAQ system with hybrid ADC technology


2. Alias-free, high dynamic mode: Sampling up to 1MS/s and up to 150dB dynamic range. The data is totally alias-free, so all higher frequencies are fully rejected. This alias-free filter with a bandwidth close to the Nyquist criterion is used for frequency domain analysis of signals such as sound and vibration. There is some ringing/overshoot on square waves and other impulse signals, a behaviour similar to classical sigma-delta ADCs, except with a much higher sample rate and bandwidth. Even though test operators may


select some channels to be high bandwidth and some to be alias- free and high dynamic range, and potentially select different sample rates for each channel, filtering is designed in such a way that signals are time-aligned with each other. Preventing phase shift is an important consideration, especially when channels are used for phase comparison, for example in modal analysis, power quality, torque vs. angle and related applications. Several instruments have taken


advantage of hybrid ADC technology so far, the first being the Sirius XHS high-speed data-acquisition system from Dewesoft. Higher sampling rates create a


demand for faster data transfer. USB 3.0 is used in these new systems, because it provides ten times the data rate of USB 2.0. Additionally, a


gigabit LAN interface allows multiple DAQ systems to be distributed and synchronised using PTPv2 (Precision Time Protocol) technology. PTPv2 provides ~1µs clock accuracy across the network, essential for synchronising DAQ and other systems. Breakthroughs in one area often


cause a cascade effect of technology advances in related areas. For example, it would be self-defeating to use signal conditioners with lower bandwidths in front of an ADC with 15MS/s sampling and a 5MHz bandwidth. So, products incorporating hybrid ADC technology require upgraded signal conditioners for popular input types such as low voltage, high voltage, IEPE accelerometers and microphones. Applications that directly


benefit from hybrid ADC technology include: Electric motor power studies –


the combination of high-bandwidth inputs with high voltage and current signal conditioning is critical in this demanding application field. Ever-increasing inverter frequencies require DAQ bandwidths of over 2MHz for sufficient acquisition and analysis. The better-than-24bit vertical axis resolution makes possible detailed harmonic analysis, normally not achievable with 16-bit systems. The rapidly-advancing technologies behind electric vehicles has made this


24 February 2022 www.electronicsworld.co.uk


an imperative field of study today. Impact testing – impact tests are


performed across a wide range of industries. For example, there are “drop shock test” applications for all kinds of products. Applications include vehicle crash testing, packaging and product life testing, and more. These tests involve one or more initial transient impulses followed by vibrations that need to be captured with the highest possible vertical axis resolution. Explosive testing – These are ballistics


and ordnance tests, which produce high- speed transients. In these applications, high-impulse signals are combined with seismic vibration data, taking full advantage of the ability to set some channels for maximum bandwidth at 16- bit resolution and others for maximum dynamic range at 24-bit resolution or better. All of these important tests benefit


from the hybrid ADC’s ability to simultaneously record very fast signals at the highest possible bandwidth, and slower signals with the highest possible dynamic range. This eliminates the need for two different DAQ systems in parallel, then finding a way to analyse and manage two sets of data.


A step forward Hybrid ADC technology is a huge step forward in the world of data acquisition. It combines the best capabilities of SAR and delta-sigma ADCs: ring-free high- speed sampling, very high dynamic range and anti-aliasing.


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