| Potentiometric sensor are widely used in chemical,environmental,sanitary,medical and other industries due to their simple structure and low cost.A wide variety of ion-selective electrodes have been developed since the study of glass membrane electrodes with selective responses to hydrogen ions by M.Cremer in 1906.In recent years,potentiometric sensors have become more intelligent and miniaturized,because of the advancement in materials,semiconductors,low-cost manufacturing technologies,Internet of Things and wireless communication technologies.Based on the current development status of potentiometric sensors,combined with embedded low-power Bluetooth wireless transmission technology this paper designed and developed a potentiometric embedded wireless sensor monitoring system based on Bluetooth low energy,which has a low-power function,powered by a 3.3V button battery,and uses an android phone or tablet with BLE function as the data receiving end to realize wireless real-time reading of the sensing potential.The monitoring system is divided into a hardware part and an embedded software part.The hardware part of the monitoring system consists of a consumption sensor and a bluetooth data acquisition board.According to the project requirements,the embedded system-on-chip(SoC)CC2541 was selected as the main controller of the monitoring system.The CA3140A was selected as the potential amplifier,and the related circuit was designed to realize real-time potential collection function of the system.The hardware circuit design mainly includes:voltage amplification module circuit design,power module circuit design,control transmission part circuit design,main controller external crystal oscillator circuit design,and on-board antenna design for data transmission and reception.The embedded software development environment has been successfully built including IAR Embedded Workbench,Bluetooth protocol stack,etc.On this basis,various functional programs were designed and developed to meet real-time update requirements of sensor data,which mainly includes:embedded initialization program design,power management program design,timing task program design,data reading and conversion program design,data transmission program design.Using the precision stabilized power supply and digital multimeter to test and verify the performance of the monitoring system,the results show that the monitoring system can respond quickly to potential changes in real time,the potential acquisition range is 0-0.75V,the potential output range is 0-5.3V,and the potential measurement can be accurate to 0.001V,the potential measurement fluctuation is±0.0004V,and the noise resistance is excellent.The pH change electrode was used to monitor the pH change in real time.The results show that the system can respond to pH changes in real time and can be used for real-time pH monitoring.The system and digital multimeter were applied to the wireless dynamic detection of L-cysteine in pig serum,and two dynamic response curves were obtained,which further showed that the Bluetooth monitoring system can realize rapid real-time monitoring of potential sensing signals.The wireless potentiometric sensor monitoring system designed and developed in this paper is compact in structure and small in size.It is easy to carry and is powered by button battery.It can be used in the field without external power supply.The monitoring system has been successfully applied to real-time monitoring of pH and the dynamic detection of L-cysteine in pig serum,which has important application prospects in the fields of life sciences. |
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