Low power AMT acquisition network based on ZigBee and GPS

Audio frequency magnetotullric (AMT) is widely used in the exploration of mineral and underground water. Three-dimension (3D) AMT exploration makes the imaging of underground geological body or structure with the best precision and resolution. And it needs a lot of AMT acquisition units to carry out exploration. Current commercial AMT unit was suffered from high power consumption and low work efficiency for 3D AMT exploration. We design and realize a low power AMT acquisition network based on ZigBee, GPS and ARM based embedded control system. Each AMT acquisition unit is composed of power supply module, GPS module, ARM module, and data acquisition module. The power supply module is controlled by the GPIO of the ZigBee Pro module. Power supply for GPS module, ARM module, data acquisition module, and induction coils can be switched on or off remotely by ZigBee network. The GPS module offers clocks and timing signals for the data acquisition module. The ARM based embedded control module is composed of AT91RM9200, 1GB NAND flash, 64 MB NOR flash, WI-FI, Ethernet and 64 MB SDRAM. It controls the data acquisition, calibration, and self-testing in AMT exploration. The data acquisition module is composed of 4 channels for the signal conditioning of weak AMT signals, 4 channels 24-bit ADC, and 24-bit fixed DSP. The low power differential amplifiers and low power audio amplifiers are used for the amplifying and filtering of the input signals. All AMT acquisition units are configured as ZigBee routers to build a wireless sensor network in mountain area successfully. A notebook with ZigBee router is used to control the AMT acquisition network. Software is developed in notebook to monitor network, send control command, retrieve the status of each AMT acquisition unit, and control the data acquisition process. One hundred AMT acquisition units are made, and tested in Tibet. The tests were successful in most area, but it was difficult to build a ZigBee network in some area where the tough topology was faced.