干燥过程中树盘含水率的在线检测

On-line Measurement of Moisture Content for Wood Disks during Drying

为实现干燥过程中树盘含水率的在线精准检测,分析了环境温度对电阻应变式称质量装置测量精度的影响规律,获得了利用环境温度和电测质量计算精准质量的二元回归方程,并用其将树盘的电测质量校正为精准质量。用树盘绝干质量、干燥过程中在线测算的精准质量计算含水率实际值,对HYD-B型含水率仪进行了实验校正。探讨了纤维饱和点之下探针深度、间距、位置及材温补偿和介质温度补偿对含水率仪测量精度的影响规律,确定适宜的探针深度和间距,得到了适宜探针深度、间距下含水率测值的修正公式。结果显示：称质量装置测量精度的二元回归校正方程的相关系数达0.99;纤维饱和点以下,探针插入木材深度距离上表面为木材厚度的1/2~2/3、间距30 mm时,含水率仪检测精度高;材温补偿和介质温度补偿对检测精度影响不大,可用方便的介质温度补偿代替材温补偿。

For improving the online detection precision of moisture content during wood drying,we studied the effect of work temperature on resistance strain type weighing device,and acquired the regression equation for evaluating exact weight based on temperature and electrical measuring weight,which was used to revise the electrical measuring weight to exact weight.We calibrated the HYD-B wood moisture content meter by accurate moisture content,which was calculated by oven dry weight and the exact weight from weighing device.We investigated the influence of the depth,interval and position of probe,temperature and medium compensation on the detection precision for wood moisture content,when wood moisture content was below fiber saturation point.The test value and actual value of wood moisture content were curve fitted and then the correction formulas were educed with the optimal probe depth and interval.The two-variable regression equation has high credibility with a coefficient of 0.99.Below fiber saturation point,there is a higher detection precision with the probe depth that is 1 / 2 to 2 / 3 of the wood thickness and the 30 mm probe spacing.The effect of temperature and medium compensation on test results is small,thus the material temperature compensation can be replaced by medium compensation.