果蔬冻干水分在线无线监测装置设计与试验

Design and Experiment of Wireless Online Device which Monitors Moisture of Fruit and Vegetable during Freeze Drying

果蔬真空冷冻干燥技术的应用推广,进行低能耗冻干工艺优化具有着重要意义。果蔬冻干工艺优化中关键技术是果蔬冻干水分的在线监测,笔者对此进行了广泛深入的探索;介绍了基于介电方法的果蔬冻干水分无线实时监测系统的设计,基本思路是:无线采集果蔬冻干过程的相对介电常数,利用实验测取的果蔬介电常数与冻干过程的含水率相关关系,实现果蔬冻干过程含水率在线检测;在冻干仓内利用集成电容转换芯片对插入果蔬内部的电极探针间电容进行采样,经过Zig Bee收发芯片无线采集测量结果,并通过上机软件将电容测量值转换为相对介电常数;在不同温度下对传感器进行校准,保证在冻干仓内加热温度下介电常数的在线精确测量。同时,以苹果和土豆为试材的试验验证,结果表明:含水率与相对介电常数有极显著的线性正相关性,无线在线检测果蔬冻干过程含水率可行。

Real-time monitoring of the moisture content of fruits and vegetables in vacuum freeze -drying process, this can provide technical support for the freeze-drying process monitoring and optimization.In order to investigate the way based on relative dielectric constant monitor the moisture content, this paper designed a wireless and real-time monitoring system which can realize relative dielectric constant acquisition, calculation and storage, it can also draw the change curve of the relative dielectric of material.The test uses apple and potato as test material to validate moisture content and relative dielectric constant has an illustrious linear correlation.Experiment has built correlation association models based on relative dielectric constant and moisture content.Therefore, moisture content of fruit and vegetables can be monitored based on its relative dielectric constant.