Dewesoft Unveils Delta-Sigma and SAR Hybrid ADC Technology Solution

Dewesoft released an innovation in the data acquisition world. For years engineers have faced a difficult choice between delta-sigma and SAR (successive approximation) ADCs (analog to digital converters) when choosing which data acquisition (DAQ) system to buy. Delta-sigma ADCs are well-known for their tremendous dynamic range, 24-bit resolution and built-in anti-aliasing filtering (AAF). However, they exhibit hysteresis, aka “ringing” when fast rising impulse signals, like the ones found in square waves, are input.

The other major ADC used in data acquisition applications is the successive-approximation (SAR) type. SAR ADCs are highly regarded for their higher sample rates, as well as for the fact that they do not exhibit ringing when impulse signals are input. But they are typically limited to 16-bits of resolution and therefore have inferior dynamic range compared to delta-sigma ADCs. SAR ADCs also lack the built-in anti-aliasing filtering of delta-sigma ADCs.

The dilemma that has faced test engineers for years is that applications that required a combination of both high-speed sampling and high-resolution with anti-aliasing filters were forced to either sacrifice one of these capabilities, or buy two completely separate DAQ systems and operate them simultaneously. Unfortunately, using two instruments doubles the amount of equipment and setup time required, increasing costs dramatically. It also makes data analysis much more complex afterwards, merging and time-aligning two completely data sets together.

Dewesoft has addresses this problem with Hybrid ADC technology, which is built into their SIRIUS XHS data acquisition system. Hybrid ADC combines the best capabilities of both major ADC types into a single unit. It also vastly increases the sample rate per channel from the typical 200 kS/s for delta sigma and 1 MS/s for SAR to 15 MS/s. Using SIRIUS XHS with its Hybrid ADC technology, engineers can stream eight analog channels at 15 MS/s per channel continuously to disk across USB 3.0. 

Using the SIRIUS XHS and Hybrid ADC, engineers can choose from among three performance modes on each channel independently, setting each one to exactly the desired configuration:

High Bandwidth Mode (Filter Off): 15 MS/s sampling rate and 5 MHz bandwidth. This mode can perfectly acquire impulse, step, and square signals without any ringing or overshoot. Ideal for transient recording and power analysis, this mode is similar to SAR ADC behavior, except with much higher sample rate and bandwidth.

Alias-free, High Dynamic Mode: Sampling up to 1.875 MHz and bandwidth up to 1 MS/s, with 150 dB dynamic range. All higher frequencies are fully rejected, therefore the data is totally alias-free. An anti-aliasing filter with a bandwidth close to the Nyquist frequency is used for frequency domain analysis of signals such as sound and vibration. There is some ringing on square waves and other impulse signals. This mode is similar to sigma-delta ADC behavior, except with a much higher sample rate and bandwidth.

Ring-free Filtering: in addition, Hybrid ADC offers ring-free filters with no overshoot on impulse signals, while still maintaining alias-free acquisition. The measurement remains alias-free because the cut-off frequency is set automatically to 20% of the sampling frequency.

One of the most powerful capabilities of the Hybrid ADC is that each channel can be set individually to any of the three modes, and each channel can be set to a different sample rate. Finally, engineers don’t have to choose between one instrument or another, but they can use a single instrument for all of their most important applications. Even though engineers may select some channels to be high bandwidth and some to be alias-free, and even select different sample rates, filtering is designed in such a way that all signals are perfectly time aligned, with zero phase shift.

SIRIUS XHS with Hybrid ADC technology is backwardly-compatible with other instruments within the Dewesoft ecosphere, and can be synchronized with instruments like the SIRIUS DualCore, SIRIUS HD, SIRIUS HS, KRYPTON, IOLITE, DEWE-43A, and more. Like all Dewesoft instruments, SIRIUS XHS includes DewesoftX software for system setup, data acquisition, monitoring and analysis.