Study Of Observation Platform Of Frozen Soil Acoustoelectric Effect Based On Virtual Instruments

At present acoustoelectric conversion is a method in front edge to confirm frost-thawing interface. The research about acoustoelectric effect on the frozen soil model with a simulative frost-thawing interface be concerned in three measurement task: measurement of temperature, ultrasonic measurement, acoustoelectric measurement. The measurement of temperature can provide a method to to confirm frost-thawing interface and judge that whether the interface is uniform with the interface confirmed by using acoustoelectric measurement. Ultrasonic measurement will be needed to determine the Ultrasonic propagation velocity in frozen soil. And acoustoelectric measurement is uppermost measurement task.For the measurement of temperature, considering comprehensive consideration of measurement range, repeatability and sensitivity, platinum thermal resistance is selected for temperature sensor. The hardware platform of the temperature measurement system is composed of four part: platinum thermal resistance, circuit board of temperature measurement, computer assembled with PCI-4472 and the connecting wire. The software programming adopted modularization design to increase flexibility and integral efficiency.For ultrasonic measurement, National Instruments M Series high-speed multifunction data acquisition (DAQ) device PCI-6251 is selected for collection hardware. The output of TTL level signal is solved. The digit I/O of PCI-6251 will output level by means of software programming. The level can be served as synchronized signal and control the transmitter to emit.For acoustoelectric measurement, as the amplitude value of received signal is quite small, the approved receiver electrodes are made and a fitting preamplifier is selected. In addition, favorable grounding and masking is arranged for the receiving of small signal.As the hardware platform is built up, the actuarial measurements on soil model with a simulative frost-thawing interface are done. The measured data indicates that the interface confirmed by measuring temperature and the one confirmed by using acoustoelectric measurement is uniform. This also indicates that the building of the whole hardware platform is a success.