An embedded processing design for 192-channel 10–40 MS/s aero-engine optical tomography: Progress and continued DAQ characterisation

A Custom, High-Channel Count Data Acquisition System for Chemical Species Tomography of Aero-Jet Engine Exhaust Plumes

“…There are several application-level specifications necessitating a custom design in this context. The first is the ~70 m distance from photodiode preamplifiers to the test cell control room [12]. Naturally, noise pickup, cable costs and scalability for >256 beams requires a distributed DAQ architecture, similar to [13,15,16,17].…”

“…Assuming a 500 kHz maximum WMS sinusoidal dither (1f), the second harmonic will be at 1 MHz (Nyquist frequency of 2 MHz). However, this assumes only two points per period rendering a triangular wave rather than requirement of this system is that software control and in-the-field tuning of variables can be leveraged to allow adaptability of the instrument for different measurement methodologies [12,33].…”

“…5. [12]. This implements 16 fully-differential channels, each with a 1 st order 10 Hz high-pass and a 2 nd order 3 MHz low-pass response.…”

“…The lower 6bits can be truncated with minimal loss of precision. To provide software control and communications with a server within the control room, the backend of this design uses an embedded 32-bit RISC microprocessor [12]. The design of this is detailed in Fig.…”

“…While optical and mechanical challenges have been addressed [7,8] and issues surrounding tomographic reconstruction with a small number of beams and angular views have been targeted algorithmically [9,10], the increase in size and complexity of this setup has presented issues for electrical designs [7,8] and data acquisition [11]. Some of these have been covered in a 2018 I2MTC prelude to this paper [12]. The system is hosted at an aero-engine testing facility operated by Instituto Nacional de Técnica Aerospacial (INTA).…”