Low-Cost Portable High-Speed Data Logging

This research describes a low-cost design for high-speed, portable, and configurable data acquisition and logging. Drone launch from in-flight aircraft produces short-duration, impactlike peak stresses in aircraft structure. Testing environments such as on aircraft require portable data acquisition hardware systems. Commercially available data acquisition systems typically have at least one drawback of being expensive, not portable, not high speed, or not configurable. These drawbacks make it difficult to use commercial systems in field experiments such as on aircraft in flight. This research describes a data logging system that is low-cost (materials < $200), portable (< 1kg), has one single-ended high-speed analog input channel (20k samples/second), and a resolution of 12 bits. The microcontroller used is a Digilent WiFire board with a microchip PIC32MZ2048EFG100 microcontroller. This microcontroller is programmed using Simulink and is configurable in its sample rate, data type, number of channels, and resolution. Data are logged locally on an SD card using an open-source OpenLager device that was developed by drone racing company dRonin for high-speed data. Data logging is in binary format, and the 12-bit value is logged as two 8-bit (upper and lower) bytes due to limitations of the OpenLager. A MATLAB script reassembles the bytes in a postprocessing step. Performance of the prototype is compared to commercial data logging systems by simultaneous logging of one event. A hammer strike force-impulse experiment is used as a proxy for the stresses in aircraft structure during impact-like events. Conclusions and recommendations on the use of the new system and existing commercial systems are made based on the results of the experiments. The experiment was designed to log signals from a strain gage-Wheatstone bridge-amplifier system, but the prototype is configurable and may be used in any applications that require portable logging of voltage signals with sample rates in the 20 kHz range.