Multichannel subgrade temperature acquisition system based on LabVIEW and serial communication

Aimed at solving the problems of complicated external environment and impossible continuous automatic measurement in observation of subgrade temperature fields in seasonal frost region, a multichannel subgrade temperature measurement system was constructed with Pt100 RTD sensors, ATMEGA16L single chip, PCF8563 clock chip, AT45DB041D external memorizer, AD7709 AD converter and MAX3232 serial interface, the system was powered by lithium batteries. CD4051 and 74LS138 were employed to construct multichannel multiplexer, and with a 3-wire RTD improved circuit was employed to measure PT100. Automatically collecting, saving and continuously observing subgrade temperature are realized by this system. LabVIEW was used to design the PC software and exchange data with the measurement system from serial interface. Measurement experiment was carried at 10 min at interval. Nonlinear autoregressive (NAR) neural network method was employed to predict the future temperature. The result indicated both the measurement system and the PC software works correctly; NAR neural network was suitable to predict subgrade temperature. The multichannel temperature system can provide basis for analysis of subgrade temperature changing law and predict future data.