设计了一个检测食品质量的由两片纽扣电池供电、可持续工作30天左右的低功耗射频pH传感器.此传感器由一个由氧化铱(IrOx)电极和氯化银(AgCl)参比电极组成的pH电极、电压转换频率电路和无线通信电路三部分组成.电压转换频率电路将pH电极产生的灵敏度为-49.6 mV/pH的电压转换成灵敏度为-4.073 kHz/pH的频率信号,然后无线通信电路将频率信号调制后传送到阅读器.本文中用此传感器对储藏在5℃下的猪肉持续监测200 h,对储藏在30℃下的牛奶持续监测26 h,实验结果证明射频pH传感器可以用于食品pH随食品质量变化而变化的食品质量检测.射频pH传感器和阅读器系统可以实现准确、方便、长期的无线食品质量检测.%This paper designs a low-power radio-frequency pH sensor which consists of two pieces of button batteries and can work 30 days continually for monitoring the quality of food. The sensor is comprised of a pH electrode,volt-age/frequency( V/F ) convert circuit and wireless communication circuit, where the pH electrode contains iridium oxide(IrOx)and silver chloride(AgCl)sensing electrodes. The voltage/frequency(V/F)convert circuit converts a-49.6 mV/pH voltage that is produced by pH electrode into a frequency signal which sensitivity is -4.073 kHz/pH. Then,wireless communication circuit modulates the frequency signal into a modulation signal and sends it to the reader. The sensor was used to monitor the quality of pork stored under 5℃ for 200 h and milk stored under 30℃ for 26 h respectively in this paper. The experimental results show that low-power radio-frequency pH sensor can be used for monitoring the quality of food in which pH changes over food quality. The radio-frequency pH sensor and reader system is designed to achieve accurate,convenient,and long-term wireless monitoring of food quality.
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