水下MEMS壁面剪应力传感器标定不确定度分析研究

Calibration and uncertainty analysis of MEMS wall shear stress sensor

针对MEMS壁面剪应力传感器进行了标定及其不确定度分析工作。标定基于压力梯度法,使用扁平校验水槽作为主要的试验装置。测量不同壁面剪应力下的MEMS输出电压信号,通过最小二乘拟合可获得标定系数。反复进行壁面剪应力及电压测量,同时查找相关产品说明书获得壁面剪应力及标定系数的不确定度。试验结果表明,剪应力测量的相对扩展不确定度小于7%,且外流速度越大,剪应力测量的不确定度越小,因此扁平校验水槽能够提供较高精度的剪应力输入;电压测量的相对扩展不确定度小于7%,且外流速度越大,电压测量的不确定度越小,因此传感器能够可靠地用于流体壁面剪应力的测量;标定曲线具有合理的形态且拟合相关性较高,因此标定公式具有较好的可靠性。

In this paper, the calibration and uncertainty analysis of the MEMS shear stress sensor are undertaken. Shear stress is generated by the pressure gradient method, the main testequipment is the flat verification water channel. Different voltage outputs are measured ferent wall shear stress conditions, and the calibration coefficient can be got through matching the shear stress and voltage with the least square method. The shear stress uncertainty and caii- bration coefficient uncertainty can be got through measuring the pressure and voand checking the related product manual. As the resutt indicated,the uncertainty of the shear stress measurement is within 7 % , it tends to be smaller as the free-stream velocity gets higher. The uncertainty of the voltage measurement is within 7 % , and it also tends to be smaller as the free-stream velocity gets higher, so that the sensor can be used to wall shear stress mreliably. The shape of calibration curve is reasonable, its correlation coefficient of fitting is large enough,it means that the calibration equation is reliably.