A Portable Contactless Conductivity Detector Based On ARM9

A portable contactless conductivity detector for the detection of microfluidic chips is presented in this study. The detector is developed on an ARM9embedded platform. All the functions of the detector are accomplished by an ARM9processor and an independent personal computer is not required. Therefore, the detector meets the requirements of the on-site detection of microfluidic chips because of its integration and portability.The hardware of the detector includes the signal excitation part, signal conditioning part, data acquisition and display part. The excitation signal is generated by MAX038function generator chip; Signal conditioning part includes rectification, filtering, amplification; The microcontroller controls analog-digital converter; Finally, the signal is displayed on the touch screen.The software of the detector includes operating system, drivers and application programs. Operating system is made up of various system modules, such as the kernel, the object storage module, the communication module etc; drivers include the driver of analog-digital converter and digital-analog converter; application programs perform a variety of functions, such as data acquisition, real-time display of signal map, data storage function, and so on.The detector provides oscillation frequency of0-2MHz and oscillation voltage of0-20Vpp (peak to peak, Vpp). The motherboard of the detector is130mm long,102mm wide,35mm high. In order to demonstrate the analytical performance of the detector, the excitation frequency and voltage were optimized with the use of a homemade microfluidic chip. The detection limit for KC1was9.1μM at the optimal frequency of50kHz and voltage of20Vpp. Compared to the results reported previously, the detector reported in this paper not only has a smaller dimensions, which makes it truly portable, but does not compromise the detection performance.