The Hardware Design Of Instrument Used For Trace Heavy Metals Detection Of Seawater

The paper is divided into two parts. Firstly, the design of a wireless sensor node based on light addressable potentiometric sensor (LAPS) is introduced. The measurement circuit of node differs because of the different demand. Then an on-line automatic analytical instrument used to detect four kinds of trace heavy metals (Zn, Cd, Pb, Cu) of seawater is introduced, which uses the method of differential pulse stripping voltammetry (DPSV).The developing wireless sensor network (WSN) can be involved to the detection of trace heavy metals. Wireless sensor network has provided a new method of getting and dealing with information. The wireless sensor node uses MSP430 as the control unit to achieve the detection with the measuring circuit and wireless transfer circuit. The LAPS node measures the weak AC signal while the electrochemistry node measures the weak DC signal. So the LAPS node uses MSP430FG4619 as the control chip, and AD5933 as the core of measurement circuit, and CC2500 as the wireless transfer chip. The electrochemistry node uses MSP430F5438 as the control chip, and ADS 1251 as the core of measurement circuit, and CC2420 as the wireless transfer chip which supports the Zigbee protocol.The instrument contains two parts in function, the measuring system and controlling system. The measuring system uses the method of DPSV. The electrochemical measurement system used to perform DPSV measurement is constructed with two parts. A low-current measurement system consists of low input bias current operational amplifier and a high resolution ADC and a potentialstat consists of high resolution DAC and high current buffer amplifier. The core of control system consists of MCU DS80C320 and Programmable System Device PSD854F2. The control system configs the parameters of the state of the pumps and valves to achieve complicated operation automaticly.A few performance testings of wireless sensor node and the instrument are carried out. Signal source resolution, current resolution, power consumption and the distance measurement of wireless transmition are implemented to the wireless sensor node. Current resolution and stability testing of potentiostat are implemented to the instrument. The testing results prove that the hardware design have met the requirements. Now our wireless sensor node and instrument are under testing in our lab. The results prove that our system is fit for our requirment.