Multipoint Data Acquisition System for Thermal Analysis of Electronic Modules

This paper focuses on the design and the implementation of a multi-input data acquisition system that is dedicated for thermal analyses of electronic assemblies. The acquisition module is capable to realize accurate, safe and reliable multipoint temperature measurements in a range from -35 degrees C until 140 degrees C. Thermal analysis is realized using multiple LM35 sensors placed in critical points of the tested modules. The main component of the system is the PIC18F4550 microcontroller, a low-power and versatile device that provides all necessary resources for acquiring and processing up to ten analog input signals. The number of input channels can be relatively easily increased by using an external high-speed multiplexer. Relying on the internal analog-to-digital converter existent in the structure of the microcontroller, the proposed system operates with a resolution of 10 bits and a maximum sample rate of 40 kS/s for each input channel. The acquired data are processed and graphically displayed using a dedicated Lab VIEW software application running on an external PC. The connectivity between the data acquisition system and the PC is realized through USB interface. Compared with the analysis methods based on thermal cameras, the proposed solution has the advantage of a lower cost, the obtained results are easy to interpret and, in many cases, the accuracy is similar or even better, especially when test are performed on series of electronic modules with configurations that generate reflections.